Patent Publication Number: US-10789137-B2

Title: Fast system state cloning

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/728,347, filed Oct. 9, 2017, which is a continuation of U.S. patent application Ser. No. 15/089,837, filed Apr. 4, 2016, which is a continuation-in-part of U.S. patent application Ser. No. 14/804,175, filed on Jul. 20, 2015, which in turn claims the benefit of U.S. Provisional Patent Application Ser. No. 62/148,160, filed on Apr. 15, 2015. U.S. patent application Ser. No. 15/089,837 also is a continuation: in: part of U.S. patent application Ser. No. 13/908,239, filed Jun. 3, 2013, which in turn is a continuation-in-part both of application Ser. No. 13/797,093, filed on Mar. 12, 2013, and of application Ser. No. 13/756,921, filed on Feb. 1, 2013. U.S. patent application Ser. No. 15/089,837 claims the benefit of U.S. Provisional Patent Application Ser. No. 62/202,983, filed on Aug. 10, 2015. The entire disclosure of each of the afore-referenced priority applications is incorporated by reference into the instant specification. 
    
    
     BACKGROUND 
     Field 
     Embodiments of the present invention generally relate to system cloning and, in particular, to a fast apparatus and method to clone a system for backup or replication. 
     Description of Related Art 
     Computer systems of varying scopes or deployment are used throughout a typical large enterprise. Enterprise-level computer systems are systems that may be used throughout an enterprise or to support enterprise-critical functions. For example, for an airline company, a reservation and booking system or a flight scheduling system may be an enterprise-level system. At a lower level of deployment, other systems (e.g., a department-level or functional-level system) may support a departmental-level organization or support a limited function. For example, department-level systems for an airline company may support one of accounting, sales and marketing, engineering, maintenance support, and so forth. At an even lower level, a computer system (either a real system or a virtual system such as a cloud-based system) may support individual employees. 
     A computer system may be characterized by its hardware and software assets, status, system state, and the like. Hardware characterization may include a list of servers used, memory and memory storage space available, communication links available, router connectivity, and so forth. Characterization of software assets may include a list of operating systems and application programs available on each server. Characterization of system state may include a list of what software is presently executing on each server, the state of each software (e.g., as indicated by a finite state machine model), data in volatile and non-volatile memory accessible to and/or used by each software, and so forth. 
     At times, it is necessary or desirable to clone a computer system, e.g., for backup or capacity purposes. For example, a backup of a computer system may be made by cloning all or part of the computer system, e.g., cloning at least the system state but not necessarily the hardware characterization. On the other hand, cloning by way of replication may be made when it is necessary to quickly ramp up processing capacity or capabilities. For example, an online retail merchant may want to replicate temporarily its computer systems devoted to sales and marketing during the period from Thanksgiving to Christmas, and release those assets later. However, the online retail merchant may want to replicate temporarily its computer systems devoted to accounting at the end of its fiscal year. 
     At times, it is necessary or desirable to restore a computer system from backups. For example, if a sales system or web site of an online merchant crashes, the merchant may not have any sales until the sales system or web site is restored. Therefore, there would be a need to restore such systems from backups as soon as possible. 
     Existing methods for cloning systems suffer from a variety of drawbacks. For example, a hot standby (e.g., a system that is constantly active and mirroring the state of a primary system) may be expensive in terms of hardware required, software licenses needed and maintenance cost (e.g., for utilities and staff), particularly for larger systems. Multiple virtual machines and hypervisors are also potentially expensive in terms of hardware and software if they are constantly kept hot. Cold standby backup systems (e.g., a backup brought online only when needed, such as upon primary system failure) may take an undesirably long time to take over for a failed system, and may not reflect the most recent state of the primary system prior to failure. 
     Therefore, a need exists to provide a system and method to clone computer systems quickly yet at low cost. 
     BRIEF SUMMARY 
     In one embodiment, a system clone is made by copying all or part of the present memory contents of an application server system, using fast methods and architecture described herein. The system clone then may be used as a backup, to increase enterprise capacity, to repurpose computing assets, and so forth. 
     A method to clone a source computing system in accordance with an embodiment of the present disclosure may include the steps of selecting a memory space coupled to the source computing system, retrieving uncoded data from the selected memory space, encoding the uncoded data by use of a bit-marker-based encoding process executing on a backup server, storing encoded data in a protected memory coupled to the backup server, wherein the protected memory is protected from a power interruption, retrieving the encoded data from the protected memory, and decoding the encoded data onto a target computing system, wherein the target computing system is separate from the source computing system. 
     A system to clone a source computing system in accordance with an embodiment of the present disclosure may include a processor coupled to a memory, the memory providing a memory space for the source computing system, a communication interface to support retrieval of uncoded data from the memory space, an encoder to encode the uncoded data by use of a bit-marker-based encoding process executing on a backup server, a storage module to store encoded data in a protected memory coupled to the backup server, wherein the protected memory is protected from a power interruption, a communication interface to support retrieval of the encoded data from the protected memory, and a decoder to decode the encoded data onto a target computing system, wherein the target computing system is separate from the source computing system. 
     The preceding is a simplified summary of embodiments of the disclosure to provide an understanding of some aspects of the disclosure. This summary is neither an extensive nor exhaustive overview of the disclosure and its various embodiments. It is intended neither to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure but to present selected concepts of the disclosure in a simplified form as an introduction to the more detailed description presented below. As will be appreciated, other embodiments of the disclosure are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and still further features and advantages of the present invention will become apparent upon consideration of the following detailed description of embodiments thereof, especially when taken in conjunction with the accompanying drawings wherein like reference numerals in the various figures are utilized to designate like components, and wherein: 
         FIG. 1  illustrates a functional block diagram of a personal computer (PC) based server as known in the art; 
         FIG. 2  illustrates a functional block diagram of a PC-based cloning server in accordance with an embodiment of the present disclosure; 
         FIG. 3A  illustrates a system in accordance with an embodiment of the present disclosure; 
         FIG. 3B  illustrates another system in accordance with an embodiment of the present disclosure; 
         FIG. 3C  illustrates a system with a virtual server, in accordance with an embodiment of the present disclosure; 
         FIG. 4  illustrates a memory model in accordance with an embodiment of the present disclosure; 
         FIG. 5A  illustrates a method to encode data in accordance with an embodiment of the present disclosure; 
         FIG. 5B  illustrates a method to decode data in accordance with an embodiment of the present disclosure; 
         FIG. 6A  illustrates a process to perform a blink backup of a source system, in accordance with an embodiment of the present disclosure; and 
         FIG. 6B  illustrates a process to restore a system from a blink backup, in accordance with an embodiment of the present disclosure. 
     
    
    
     The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include”, “including”, and “includes” mean including but not limited to. To facilitate understanding, like reference numerals have been used, where possible, to designate like elements common to the figures. Optional portions of the figures may be illustrated using dashed or dotted lines, unless the context of usage indicates otherwise. 
     DETAILED DESCRIPTION 
     The disclosure will be illustrated below in conjunction with exemplary use cases, method embodiments, and system embodiments. Although well suited for use with, e.g., a system using servers, networking equipment and/or specialized instrumentation, the disclosure is not limited to use with any particular type of electronic system or configuration of system elements. Those skilled in the art will recognize that the disclosed techniques may be used in any electronic system in which it is desirable to replicate, clone, backup or restore a computer system. 
     Embodiments in accordance with the present disclosure will be described in relation to associated hardware. However, to avoid unnecessarily obscuring the present disclosure, the following description omits well-known structures, components and devices that may be shown in block diagram form, are well known, or are otherwise summarized. It should also be noted the examples presented herein should not be construed as limiting of the scope of embodiments of the present invention, as other equally effective examples are possible and likely. 
     As used herein, the term “module” refers generally to a logical sequence or association of steps, processes or components. For example, a software module may comprise a set of associated routines or subroutines within a computer program. Alternatively, a module may comprise a substantially self-contained hardware device. A module may also comprise a logical set of processes irrespective of any software or hardware implementation. 
     A module that performs a function also may be referred to as being configured to perform the function, e.g., a data module that receives data also may be described as being configured to receive data. Configuration to perform a function may include, for example: providing and executing computer code that performs the function; providing provisionable configuration parameters that control, limit, enable or disable capabilities of the module (e.g., setting a flag, setting permissions, setting threshold levels used at decision points, etc.); providing a physical connection, such as a jumper to select an option, or to enable/disable an option; attaching a physical communication link; enabling a wireless communication link; providing electrical circuitry that is designed to perform the function without use of a processor, such as by use of discrete components and/or non-CPU integrated circuits; energizing a circuit that performs the function (e.g., providing power to a transceiver circuit in order to receive data); and so forth. 
     The parent of the present patent application (U.S. patent application Ser. No. 14/804,175, “the &#39;175 Application”) discloses a system for a high-capacity and fast transfer rate digital storage. Bit marker technology used in the &#39;175 Application and herein is described in CIP parent application U.S. patent application Ser. No. 13/908,239 (“the &#39;239 Application). When a computer system can be characterized at least in part by a digital state of its software assets, status and system state, then embodiments in accordance with the present disclosure may use the system of the parent disclosure in order to clone a digital state very quickly. System restoral may be performed commensurately quickly. 
     The methods, components and systems disclosed in the &#39;175 Application and used in the present embodiments include a hypervisor, a server processor, a customized operating system and/or a guest operating systems (OSs) in the hypervisor, data or drives associated with the guest OSs. Embodiments are able to integrate into substantially any network via networking components (e.g., Ethernet adapters). Embodiments may further include conventional RAM volatile memory, and a non-volatile DIMM memory (NV-DIMM) that is protected from data loss as disclosed in the &#39;175 Application. Systems may further include PCIe, peripheral devices and structuring. 
     The data being imaged and represented may include substantially any data stored in the volatile RAM, e.g., databases, application programs, logs, proprietary data, and so forth. Application programs may include: various services executing at an operating system level such as a firewall service, a document service, etc.; various software executing at a user level such as a spreadsheet, word processor, graphics editing, CAD/CAM software, accounting software, etc.; and various servers, such as a web server, a mail server, a database server, and so forth. 
       FIG. 1  illustrates a functional block diagram of a conventional computer system  100  as known in the art. System  100  may be used, for example, in a computer system based upon an Intel®-compatible architecture. As fabrication technology advances, various functional components may be fabricated in different integrated circuit (IC) configurations, depending upon factors such as generation of chipset, price-to-performance ratio of the targeted customer, targeted computing platform (e.g., mobile devices, servers, etc.), and so forth. Certain functions may be combined into various configurations such as in a single IC, such as an IC  116 . 
     System  100  includes a processor  102 , which may be a general-purpose processor such as Xeon®, Intel Core i7®, i5®, i3®, or processors from Advanced Micro Devices® (AMD) such as Athlon64®, and the like. In other embodiments, processor  102  may be a graphics processing unit (GPU). In the functional block diagram of  FIG. 1 , processor  102  as used herein may refer to the functions of a processor, and/or refer to the one or more hardware cores of a processor. Processor  102  may include multiple processing cores that operate at multi-GHz speeds. Processor  102  may include a cache memory  103  (e.g., L1 or L2 cache). Processor  102  also may be programmed or configured to include an operating system  104 . Examples of operating system  104  include various versions of Windows®, Mac OS®, Linux®, and/or operating systems or operating system extensions in accordance with an embodiment of the present disclosure, and so forth. The registered trademark Windows is a trademark of Microsoft Inc. The registered trademark Mac OS is a trademark of Apple Inc. The registered trademark Linux is used pursuant to a sublicense from LMI, the exclusive licensee of Linus Torvalds, owner of the mark on a world-wide basis. Operating system  104  performs conventional functions that include the running of an application program (not shown in  FIG. 1 ). Functionally, operating system  104  is illustrated as being a part of processor  102 , but portions of operating system  104  may physically reside in a non-volatile memory (e.g., a hard disk, solid-state drive (SSD), flash drive, NAND memory, non-volatile RAM, etc.), not illustrated in  FIG. 1 , and at least portions of operating system  104  may be read into RAM memory as needed for execution by processor  102 . 
     Processor  102  may use several internal and external buses to interface with a variety of functional components. System  100  includes communication bus  105  that links processor  102  to memory controller  106 . Memory controller  106  may also be referred to as a northbridge. Communication bus  105  may be implemented as one of a front side bus (FSB), a Non-Uniform. Memory Access (NUMA) bus, an EV6 bus, a Peripheral Component Interconnect (PCI) bus, and so forth. 
     System  100  further includes a nonvolatile memory  122  (e.g., a CMOS memory) coupled to processor  102 . CMOS memory  122  may include a basic input/output system (BIOS)  124 , which helps manage low-level communication among computer components, and may include storage of computer code to perform a power-on self-test. Conventionally, a power-on self-test may include a test of the data integrity of installed RAM. 
     Memory controller hub  106  typically handles communications between processor  102  and various high-speed functional components such as external RAM memory installed in dual in-line memory module (DIMM) slots  108   a ,  108   b  via communication bus  107 , and video graphics card  110  via communication bus  109 . Communication buses  107  and  109  may be high-speed interfaces, such as Peripheral Component. Interconnect Express (PCIe) or Accelerated Graphics Port (AGP). Memory controller hub  106  may also handle communications between processor  102  and controller hub  114 , via communication bus  112 . Controller hub  114  may also be known by other names such as a southbridge, an I/O Controller Hub (ICH), a Fusion Controller Hub (FCH), a Platform Controller Hub (PCH), and so forth. Controller hub  114  in turn manages further communication with additional and/or slower I/O devices or interfaces such as USB ports  131 , storage media  132  with standard interfaces (e.g., ATA/SATA, mSATA, SAS, etc.), Ethernet transceivers  133 , audio ports  134 , other PCI devices  135 , and so forth. 
     In some configurations of system  100  (not illustrated), processor  102  is designed to bypass memory controller  106  and communicate directly with controller hub  114  via a Direct Media Interface (DMI). Such configurations also may integrate the functions of processor  102  and memory controller  106  into a single IC  116 . In such configurations, controller hub  114  is typically a Platform Controller Hub (PCH). 
     Although the memory chips that make up RAM memory installed in DIMM slots  108   a ,  108   b  may have a very high maximum access speed (e.g., about 57 GBytes/sec), communication bus  109  normally cannot support such fast speeds. For example, the speed of PCIe 4.0 in a 16-lane slot is limited to 31.508 GBytes/sec. AGP is slower still than PCIe. Therefore, communication bus  107  is a bottleneck that prevents faster memory access. 
     The bottleneck of memory access is one drawback of the conventional art. Other drawbacks described above of a conventional computer include the mismatch in storage size between the size of RAM memory (typically on the order of a few Gbytes) and the storage size of a conventional hard disk (typically on the order of a few Tbytes), and the relatively small storage size of RAM memory to the storage size of a conventional hard disk. Another drawback of the conventional art is the volatile nature of the RAM memory. 
     Embodiments in accordance with the present disclosure break the density issue that RAM has today. Embodiments in accordance with the present disclosure address these drawbacks of the conventional art by providing a novel hardware interface for storage units, and a novel driver interface for the hardware interface. 
     Outside of the CPU, RAM is the fastest element in x86 and x64 computing systems, so embodiments allows for the alignment of today&#39;s high speed RAM performance with a new method of achieving high storage density. As this effect is applied, it completely changes the cost paradigm and allows low cost memory modules to replace the need for high-density, high cost memory modules. 
     A remaining issue is the volatility of standard memory modules. Since all RAM is volatile, it does not lend itself to becoming a long-term storage medium. Embodiments are similar to but differ from non-volatile RAM (NVRAM) technology, which circumvents the volatility issue found in standard DIMM devices. 
     Embodiments in accordance with the present disclosure use a basic inexpensive x64 motherboard that can be powered by Intel® or AMD® CPU processors. The motherboard has a modified CME and BIOS that gives it the intelligence required to be Non-Volatile Memory aware. In addition, the motherboard provides to each memory module a DC supply voltage (e.g., 1.2 v, 1.35 v, 1.5 v, etc.) that may be used to charge environmentally-safe low-load, slow-drain capacitors. This design allows for shutdown state (e.g., loss of power or safe shutdown) to maintain data persistence within the memory module, thus making the memory module a viable long-term storage device. 
       FIG. 2  illustrates a functional block diagram of a computer system  200  in accordance with an embodiment of the present disclosure. Computer system  200  may also be referred to herein as a blink server. Functional components already described in  FIG. 1  are assigned in  FIG. 2  the same reference number as that shown in  FIG. 1 . System  200  includes a memory interface  218 , which may be physically coupled to a DIMM slot (e.g., DIMM slot  108   b ) by use of a connector  208  such as a Molex® connector. Memory interface  218  communicates with processor  202  through DIMM slot  108   b  by use of conventional protocols on communication bus  107 . Memory interface  218  is coupled physically and communicatively to RAM storage unit  220 . Functions of memory interface  218  include communicatively coupling RAM storage unit  220  to communication bus  107 , monitoring for certain events like state of health related to RAM storage unit  220 , other hardware events, taking certain actions based upon detected signals or hardware events, and so forth. Functions of memory interface  218  also may include simple processing and housekeeping functions such as resolving memory addresses, reporting memory size, I/O control, keeping track of and reporting total power cycles, run time in an hour, reporting number of DIMMs, reporting status such as ultra capacitor (cap) current voltage, bus ready, last restore success or failure, device ready, flash status of the NAND area, cap connected, cap charge status, valid image present, DIMM init performed, read registers, and so forth. NAND may be known as a type of non-volatile IC-based storage technology that does not require power to retain data. 
     System  200  further includes a nonvolatile memory  222  (e.g., a CMOS memory) coupled to processor  202 . CMOS memory  222  may include a basic input/output system (BIOS)  224 , which helps manage low-level communication among computer components, and may include storage of computer code to perform a power-on self-test. Conventionally, a power-on self-test may include a test of the data integrity of installed RAM. Embodiments in accordance with the present disclosure may include a modified power-on self-test (as compared to the power-on self-test of BIOS  124 ), such that the power-on self-test may skip the test for at least some predetermined memory modules, e.g., if the test would be incompatible with the nature of data stored in the predetermined memory module. 
     Embodiments in accordance with the present disclosure also address the RAM volatility shortcoming of the known art by coupling an energy source  219  with RAM storage unit  220 . Energy source  219  may be incorporated with memory interface  218 . Energy source  219  is a source of backup power, such that if an external power supply to RAM storage unit  220  is lost (e.g., by way of an AC power failure affecting the entire computing system  200 , removal of a battery powering a mobile system  200 , motherboard failure, etc.), energy source  219  may provide sufficient power in order to maintain integrity of data stored in RAM storage unit  220 . 
     Embodiments in accordance with the present disclosure include random access memory (RAM) organized as a combination of traditional volatile memory and non-volatile RAM module memory (NV-DIMM). The NV-DIMM memory is disclosed in the parent U.S. patent application Ser. No. 14/804,175 (“the &#39;175 Application”), e.g., as the RAM storage unit  220 . The proportion of each type of memory of the whole that is installed in a system may vary from system to system. For example, the total memory size may be selected at installation to be within a range of 8 GB to 160 GB or more, organized in eight banks, with two of the banks configured as conventional RAM memory and six banks configured as NV-DIMM. 
     Embodiments in accordance with the present disclosure may provide a system that operates in two modes. In a first mode, the entire content or address range of a conventional volatile memory of a source system (either of the present system or of an external system) may be selected to be imaged and represented by use of the methods disclosed in the &#39;175 Application, and the representation stored in the NV-DIMM memory. This image or representation may also be known as a reference image. Embodiments may be communicatively coupled to an external system by use of a high-speed communication link such as 100 Gigabit Ethernet conforming to the IEEE 802.3ba-2010 standard. 
     In a second mode in accordance with an embodiment of the present disclosure, a subset of the entire conventional volatile memory address range of a source system may be selected to be imaged and represented, e.g., only a portion of the conventional volatile memory that is actively being utilized by processing running on the system being imaged and represented. In another variation of this embodiment, a fixed range subset of the entire conventional volatile memory address range may be imaged and represented. The fixed range subset does not necessarily need to be contiguous. In another variation of this embodiment, the subset of the address range being imaged and represented may represent a virtual server. For example, if a single physical server (e.g., used by a business enterprise) hosts more than one virtual server (e.g., one each for several departments in the business enterprise), embodiments may image and represent some but not all of the virtual servers. Such a capability may be useful if, e.g., the functions performed by the different servers have different backup needs (e.g., a virtual server for the finance department vs. a virtual server for the customer support department). 
     In some embodiments, the NV-DIMM may act as a repository to store a plurality of reference images representing, e.g., a single system over time, or multiple external systems, or a combination thereof. An NV-DIMM repository of multiple reference images may be used to support disaster recovery, e.g., an off-site location securely storing reference images for multiple enterprises. 
     After the data has been imaged, represented and stored in NV-DIMM memory, embodiments in accordance with the present disclosure may provide an “infrastructure in a box” capability. For example, once all the databases, applications, logs, proprietary data, and so forth that had been imaged and represented is replicated on a target hardware environment that mimics the original hardware environment, the system that had been imaged and represented may be replicated along with the system state of the original system at the time it had been imaged and represented. 
     A replicated copy may be useful for backup purposes with fast restoration, or to be able to provide expanded capacity on short notice. Whether a restoration is deemed fast may vary from one field of use to another, or one content to another. For example, a fast restoration for a CAD/CAM system may not be deemed to be a fast restoration for a computing system supporting financial market trading. A fast restoration for a computing system providing video distribution of movies on demand may not be deemed to be a fast restoration for a computing system providing video distribution of a live event like the Super Bowl. Similarly, what notice is deemed to be short notice may vary from one field of use to another or one content to another, and may be as short as a few seconds or less for a computing system that supports financial market trading. In some embodiments, short notice is less than about five seconds notice. In some embodiments, a fast restoration can be completed within about ten minutes of the detection of a need for restoration or receipt of a command to perform a restoration. In other embodiments, a fast restoration can be completed within about three minutes. In other embodiments, a fast restoration can be completed within ten seconds or less. 
     Traditional backups are a relatively infrequent occurrence (e.g., once per day, once per week, etc.) in which a system state must be frozen or at least changes to system state should be minimized during a traditional backup process (e.g., by users saving their work, exiting out of applications, etc., all of which cause disruption). In contrast, when replicated copies may be made more quickly, backups can be made more quickly, more timely, and more frequently, resulting in a more recent (i.e., less stale) copy of a system state in case a restoration is necessary. Frequent backups begin to resemble a snapshot of a system state. Frequent backups may be referred to herein as “blink” backups. 
     Changes to system state may be reduced during a blink backup, as described below in greater detail with respect to  FIG. 3C . The frequency of blink backups may be configurable by a user or system administrator. 
     Analogizing to photography, a traditional backup is like a formal holiday family portrait that requires preparation (e.g., interrupting other activities in order to have the portrait taken, and staging—i.e., special poses, lighting, props, etc.). In contrast, embodiments are more like a video recording of a family, with each individual frame of the video representing a separate blink backup (albeit at a relatively slow frame rate compared to a video recording). The blink backup occurs quickly without necessarily requiring undue preparation, and therefore can be made frequently without disrupting operation of the system being blinked. 
     A blink backup may proceed first by identifying memory resources to be backed-up. For example, suppose an application-specific server is to be backed up. For example, the application-specific server to be backed up may be a virtual server dedicated to accounting functions, the virtual server being hosted on a physical server along with other virtual servers dedicated to other functions respectively such as sales and marketing, engineering department, etc. The server to be backed up customarily will keep a list of application programs executing on itself, along with their respective system resource usage. Embodiments may identify all system resources used by the application-specific server, as indicated by RAM memory ranges allocated to or used by all application programs currently running on the application-specific server being backed-up, address ranges of program code stored in a nonvolatile memory (e.g., storage media such as hard disk, solid-state drive (SSD), flash drive, NAND memory, non-volatile RAM, etc.), operating system configuration, and so forth. Embodiments may perform this collection as a high-priority data collection task, in order to minimize state or data changes to other application programs running on the application-specific server while the collection is taking place. The data collection task does not need to report its own memory usage. 
     Next, embodiments may retrieve the memory contents indicated by the identification task. Embodiments may then encode and store the memory contents in accordance with process  500  of  FIG. 5A , described below in greater detail. 
     In some embodiments, a replicated copy may be generated by request from a source external to the system being replicated (e.g., a “pull” basis). In other embodiments, a replicated copy may be generated at a time determined by the system being replicated (e.g., a “push” basis). A push basis is similar to a scheduled backup. 
     Embodiments in accordance with the present disclosure also provide an ability to repurpose a computer hardware architecture upon short notice. For example, suppose that a web hosting company hosts several disparate web sites of interest, e.g., an e-commerce web site like Amazon™ using an average of 200 servers, an online trading web site like E-Trade™ using an average of 100 servers, and so forth. Further suppose that they use the same or similar computer hardware architecture constructed from standard components. The software components may be different, e.g., the e-commerce web site may be based upon an open-source operating system like Linux™, and the online trading web site may be based upon a commercial operating system like Microsoft Windows™. Utilization may vary over time, such that when one system is highly utilized the other system may be lightly utilized, and vice versa. In such a scenario, embodiments may quickly repurpose some servers from one web site to another. For example, if in the middle of a weekday the e-commerce web site is not busy but the online trading web site is busy, some number of servers (e.g., 40 servers) could be repurposed from e-commerce to online trading. Conversely, on a weekday evening when the e-commerce web site is busy but the online trading web site is not busy, some number of servers (e.g., 50 servers) could be repurposed from the online trading web site to the e-commerce web site. The repurposing may also be referred to as personality swapping. 
     For a server being repurposed from purpose “A” to purpose “B”, repurposing may involve first copying or cloning a system state of a server currently devoted to purpose “B”. The system state may include all memory currently being used, the operating system and all software currently executing, and so forth. Optionally, the current system state of the server currently devoted to purpose “A” but which will be repurposed may be saved for later restoration. Next, the system state cloned from purpose “B” will be restored on the server that was formerly devoted to purpose “A”, thereby substantially instantaneously repurposing that server to purpose “B”. 
     When repurposing, purpose “A” and purpose “B” may be substantially any server-based application, for either the same enterprise or different enterprises. For example, for a single enterprise such as a major toy retailer, purpose “A” may be sales systems that are in most demand before Christmas, and purpose “B” may be accounting systems that are in most demand at the end of the fiscal year. 
     Similarly, embodiments in accordance with the present disclosure may increase system capacity by repurposing servers from a spare status to an active status for a particular purpose. A spare status may be, e.g., a blank system that is populated with hardware but does not have usable software or data installed. 
     Embodiments in accordance with the present disclosure may facilitate combinations of system images. For example, a base system image may represent the operating system and/or certain computing infrastructure for the operating system, e.g., uncustomized servers such as a web server, a mail server, and so forth. The base system image may then be merged combined) with a custom image, which may represent system-specific customizations of the uncustomized servers, e.g., user accounts, histories, preferences, macros, specialized application programs, and so forth. Conversely, system blinks may be able to blink the customizations separately from the base system image, allowing the customizations to be backed up on a different schedule or with less latency compared to a backup of the base system image. 
       FIG. 3A  illustrates a system  300  in accordance with an embodiment of the present disclosure. System  300  may be used to perform fast cloning. System  300  as illustrated includes an enterprise A  301 -A, an enterprise B  301 -B and enterprise C  301 -C. Each enterprise may represent an entire company or organization, e.g., a gaming network, an online merchant, an online brokerage, a stock exchange, etc. System  300  may include fewer or more enterprise networks than depicted in  FIG. 3A . 
     Each enterprise  301 - n  may include one or more servers, e.g., servers  303 -A- 1  through  303 -A-n for enterprise A  301 -A, servers  303 -B- 1  through  303 -B-n for enterprise B  301 -B, and servers  303 -C- 1  through  303 -C-n for enterprise C  301 -C. Individual servers within an enterprise may be utilized by the enterprise for different functions. For example, if enterprise A  301 -A is an online merchant, then server  303 -A- 1  may be a web server, server  303 -A- 2  may be devoted to database and inventory management, server  303 -A- 3  may be devoted to billing and accounting, etc. 
     Each enterprise  301 - n  may be communicatively coupled to cloning server  305  through communication network  308 . Cloning server  305  may be, e.g., computer system  200  as illustrated in  FIG. 2 . In operation, cloning server  305  may perform the process embodiments described herein upon external servers  303 - m - n . For example, cloning server  305  may replicate server  303 -B- 1  onto server  303 -B- 2 , or cloning server  305  may make a blink backup of server  303 -C- 1 , and so forth. 
     In some embodiments, an optional separate blink repository  306  may store blink backups from one or more servers  303 . Without a separate blink repository  306 , blink backups may be stored within NV-DIMM memory of cloning server  305 . 
       FIG. 3B  illustrates a system  350  in accordance with an embodiment of the present disclosure. System  350  may be used to perform fast cloning of an application server  351  without the need for external access through a network. System  350  includes application server  351 , which may be ordinary functions, for example, a web server, or a database server, or an accounting server, etc. Application server  351  may include a processor  352  coupled to conventional volatile RAM memory  353  and storage media  354  to support operation of application server  351  in its ordinary function. Communication interface  355  may provide communication connectivity between application server  351  and an external communication link (e.g., an Ethernet interface to a WAN or LAN). 
     However, application server  351  may have further embedded within it the functionality of cloning server  355 , supported by conventional volatile RAM memory  307  and NV-DIMM  309 . Cloning server  355  may be, e.g., computer system  200  as illustrated in  FIG. 2 . In operation, cloning server  355  may perform the process embodiments described herein upon application server  351 . An advantage of system  350  compared to system  300  is that system  350  does not necessarily need access to a communication network such as communication network  308 , because cloning server  355  is embedded within application server  351 . Embedding may be accomplished by, e.g., processor  352  of application server  351 , which executes code modules for both application server  351  and cloning server  355 . 
     Alternatively, application server  351  may be implemented using computer system  200  as a starting point, then executing by operating system  204  additional software modules that provide the functionality of application server  351 . 
       FIG. 3C  illustrates a system  370  in accordance with an embodiment of the present disclosure. System  370  includes a physical server  371 , which in turn may include a cloning server  375  and one or more of the components of application server  351  (as indicated by like reference numbers), plus one or more virtual servers  378   a  . . .  378   n  (collectively, virtual servers  378 ). An individual but nonspecific one of virtual servers  378  may be referred to as virtual server  378 . A hypervisor or other virtual machine monitor operating in processor  352  may manage physical server  371  and its resources in order to provide the appearance of virtual servers  378  to remote users, e.g., remote users coupled through communication interface  355 . Virtual servers  378  may provide a respective guest operating system (“GOS”), e.g., for the benefit of a user (e.g., a remote user) who is coupled to the respective virtual server  378 , and to support execution of application program(s) on the virtual server  378 . Memory storage to support a virtual server  378  may be allocated from RAM  353 , storage media  354 , and/or provided by an external memory device (not illustrated in  FIG. 3C ). 
     In some embodiments, upon the occurrence of a blink backup, a virtual server  378 , its respective GOS, memory resources and any application programs running on the GOS may temporarily enter a locked or suspended state for the duration of time it takes to perform the blink backup. The locked or suspended state reduces changes to system state or system configuration while the blink backup is taking place. At conclusion of the blink backup, elements that entered a locked or suspended state may automatically return to their normal state. 
     In some embodiments, a virtual server  378 , its respective GOS, memory resources and any application programs running on the GOS may temporarily enter a quiescent state during a blink backup. A quiescent state may continue to execute transactions, but results may be held in resident memory rather than being committed to storage media. In contrast, a server in a hibernation mode may save a memory image to storage media and shut down without executing transactions while in hibernation mode. At conclusion of the blink backup, elements that entered a quiescent state may automatically return to their normal state. 
     In some embodiments, blink backups may be stored in an external blink repository, similar to blink repository  306 , accessible via communication interface  355 . 
       FIG. 4  illustrates a simplified flat physical address space model. The total amount of physical memory may differ from the amount depicted in  FIG. 4 . Embodiments in accordance with the present disclosure are able to create a fast clone of an entire address space  403  using processes described herein. Other embodiments are able to make fast clones of one or more portions  401   a ,  401   b  of the simplified flat physical address space model using processes described herein. 
       FIG. 5A  illustrates an encoding process  500  in accordance with an embodiment of the present disclosure. Process  500  may be performed by operating system  204  and data adaptation module  211 . 
     Process  500  begins at step  501 , at which a block of raw data to be stored is received from an application program that intends to store the raw data. The raw data may be in the form of a file, a streaming media, a fixed-size or variable-size block of data, and so forth. 
     Next, process  500  transitions to step  503 , at which portions of the raw data received in step  501  may be mapped or matched to candidate vectors of raw data. Matching the raw data to longer candidate vectors of raw data should produce greater data storage efficiency than matching the raw data to shorter candidate vectors of raw data. The candidate vectors may be stored as a table of (marker, vector) pairs in conventional memory. The goal is to represent each bit or byte in the raw data by at least one vector. Certain raw data bytes such as 0x00 or 0xFF may be deemed to be a default value, and for any raw data bytes equal to the default value, it is optional to represent bytes equal to the default value with a vector. 
     In step  503 , a minimum threshold length limit may exist on the length of a portion of the raw data that will be mapped to candidate vectors of raw data. For example, raw data consisting of only a single byte would be too short to attempt to match to a candidate vector of raw data, because a pointer to the vector of raw data would be longer than the raw data itself. For raw data whose length exceeds the minimum threshold, if the raw data does not match an existing candidate vector of raw data, the raw data may be added as a new vector of raw data. 
     Next, process  500  transitions to step  505 , at which vectors determined in step  503  may be mapped to a respective bit marker from the table of (marker, vector) pairs. The bit marker is a short way to refer to the associated vector. 
     Next, process  500  transitions to step  507 , at which the bit marker from the table of (marker, vector) pairs is stored in memory, such as RAM storage unit  220 . 
       FIG. 5B  illustrates a decoding process  550  in accordance with an embodiment of the present disclosure. Process  550  may be performed by operating system  204  and data adaptation module  211 . 
     Process  550  begins at step  551 , at which a block of encoded data to be decoded is read from a memory, such as RAM storage unit  220 . Addresses may be managed by virtual address adjustment methods and tables, as known to persons of skill in the art. 
     Next, process  550  transitions to step  553 , at which bit markers are extracted from the encoded data. 
     Next, process  550  transitions to step  555 , at which the extracted bit markers from step  553  are searched for in the table of (marker, vector) pairs. 
     Next, process  550  transitions to step  557 , at which a raw data vector is extracted from an entry in the table of (marker, vector) pairs, corresponding to the extracted bit marker from step  553 . 
     Next, process  550  transitions to step  559 , at which the extracted raw data vectors from step  557  are combined to form reconstructed decoded data. If the combined raw data vectors do not cover all addresses within an entire expected address range of the reconstructed decoded data, the uncovered addresses may be deemed to take on a default value in the decoded data, e.g., 0x00 or 0xFF bytes. 
       FIG. 6A  illustrates a process  600  to perform a blink backup of a source system, in accordance with an embodiment of the present disclosure. Process  600  may be performed by operating system  204  and data adaptation module  211 . 
     Process  600  begins at step  601 , at which memory resources to be backed up from the source system are identified. For example, the memory resources may correspond to an entire server, or a virtual server dedicated to a particular function or group. (e.g., accounting functions), or correspond to another similar computing system. More particularly, the memory resources may correspond to one or more processes executing on a source system (i.e., a system to be backed-up). A virtual server may be hosted on a physical server along with other virtual servers dedicated to other functions respectively such as sales and marketing, engineering department, etc. 
     Next, process  600  transitions to step  603 , at which the memory contents identified in step  601  are retrieved from the source system (i.e., the system to be backed up). Control of process  600  may then transfer to encoding process  500  for further processing. The memory contents identified in step  601  may be used as the blocks of raw data input to be encoded by process  500 . The blocks of raw data may be divided in substantially any convenient way prior to transfer to encoding process  500 . For example, blocks of raw data may have substantially uniform block size (e.g., 1 Mbyte per block of raw data), or a block of raw data may correspond to a memory space used by a respective process of the server being backed up, and so forth. In some embodiments, a marker table as described in the &#39;175 Application may be referenced by more than one blink backup. 
       FIG. 6B  illustrates a process  650  to restore a system from a blink backup, in accordance with an embodiment of the present disclosure. The blink backup may also be referred to as a target system, since it was the target of the backup when the blink backup was made. Process  650  may be performed by operating system  204  and data adaptation module  211 . 
     Process  650  begins at step  651 , at which embodiments identify a system to restore. 
     Next, process  650  transitions to step  653 , at which encoded contents corresponding to the server to be restored are retrieved from an encoded memory such as NV-DIMM  309 . 
     Next, process  650  transitions to step  655 , at which a decoding process such as decoding process  550  is invoked in order to decode the retrieved encoded contents from step  653 . 
     Next, process  650  transitions to step  657 , at which the decoded data is saved into the memory space of a target system. The decoded data may be stored at the same memory addresses as it occupied on the source system. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the present invention may be devised without departing from the basic scope thereof. It is understood that various embodiments described herein may be utilized in combination with any other embodiment described, without departing from the scope contained herein. Further, the foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. Certain exemplary embodiments may be identified by use of an open-ended list that includes wording to indicate that the list items are representative of the embodiments and that the list is not intended to represent a closed list exclusive of further embodiments. Such wording may include “e.g.,” “etc.,” “such as,” “for example,” “and so forth,” “and the like,” etc., and other wording as will be apparent from the surrounding context. 
     No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. Further, the terms “any of” followed by a listing of a plurality of items and/or a plurality of categories of items, as used herein, are intended to include “any of,” “any combination of,” “any multiple of,” and/or “any combination of multiples of” the items and/or the categories of items, individually or in conjunction with other items and/or other categories of items. 
     Moreover, the claims should not be read as limited to the described order or elements unless stated to that effect. In addition, use of the term “means” in any claim is intended to invoke 35 U.S.C. § 112, ¶ 6, and any claim without the word “means” is not so intended.