Abstract:
A method for defragmenting volumes in a mirrored system. The method includes suspending one or more updates from being mirrored from a first set of tracks on a first server to a second set of tracks on a second server. A defragmenting process is performed on the second server. The defragmentation process stores a before and after mapping of the second set of tracks, wherein the before and after mapping includes information identifying at least one track of the second set of tracks and a corresponding first location of the respective track before the defragmenting and a second location of the respective track after the defragmenting. The method further includes, upon the defragment process completion, relocating at least one track of the first set of tracks on the first server according to the stored before and after mapping of the corresponding second set of tracks on the second server.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to the field of defragmenting, and more particularly to shifting a defrag operation in a mirrored system. 
         [0002]    In today&#39;s data storage environments, operations against storage volumes, also referred to as a hard disk drives (HDD), require multiple passes of disk reads and writes. A single hard disk usually consists of several platters. Each platter has the same number of tracks, and a track location that cuts across all platters is called a cylinder. 
         [0003]    Disk reads/writes are performed by disk read/write heads that are the small parts of a disk drive that move above the disk platter and transform the platter&#39;s magnetic field into electrical current reading or writing to the disk. An example of disk read/writes would be a volume defragmentation (DEFRAG). In the maintenance of file systems, defragmentation is a process that reduces the amount of fragmentation by physically organizing the contents of the storage device into the smallest number of contiguous regions (i.e., fragments). The defragmentation process also attempts to create larger regions of free space using compaction to impede the return of fragmentation. Some defragmentation utilities try to keep smaller files within a single directory together, as they are often accessed in sequence. 
         [0004]    Many known data storage systems use mirrored volumes. In data storage, disk mirroring is the replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability. A mirrored volume is a complete logical representation of separate volume copies. 
       SUMMARY 
       [0005]    Embodiments of the present invention disclose a method, computer program product, and system for defragmenting volumes in a mirrored system. The method includes suspending one or more updates from being mirrored from a first set of tracks on a first server to a second set of tracks on a second server. The method further includes a defragmenting process being performed on the second server. The defragmentation process stores a before and after mapping of the second set of tracks, wherein the before and after mapping includes information identifying at least one track of the second set of tracks and a corresponding first location of the respective track before the defragmenting and a second location of the respective track after the defragmenting. The method further includes, upon the defragment process completion, relocating at least one track of the first set of tracks on the first server from a first location on the first server to a second location on the first server according to the stored before and after mapping of the corresponding second set of tracks on the second server. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a functional block diagram illustrating a data storage environment, in an embodiment in accordance with the present invention. 
           [0007]      FIG. 2  is a flowchart depicting operational steps of defrag operation, on a mirrored volume within the data storage environment of  FIG. 1 , in an embodiment in accordance with the present invention. 
           [0008]      FIG. 3  depicts a block diagram of components of the server computer executing the defrag operation, in an embodiment in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Embodiments in accordance with the present invention recognize that a defragmentation process can result in high CPU usage and delays in data or volume read/write access. Many computer clients in today&#39;s data storage environments mirror critical disk volumes to prevent data loss. Multiple pass DEFRAG writes in a defragmentation process are also mirrored to remote sites, which leads to an increase in network traffic. As such, an alternative is required to allow for DEFRAG activity to take advantage of spare CPU cycles at the remote site to perform the required multiple pass DEFRAG activity required. 
         [0010]    Embodiments in accordance with the present invention will now be described in detail with reference to the Figures.  FIG. 1  is a functional block diagram, generally designated  100 , illustrating a data storage environment, in an embodiment in accordance with the present invention. 
         [0011]    Data storage environment  100  includes server  102  and server  116 , all interconnected over network  114 . Server  102  includes RAM  104 , central processing unit  106 , and persistent storage  108 . Server  102  may be a Web server, or any other electronic device or computing system, capable of processing program instructions and receiving and sending data. In some embodiments, server  102  may be a laptop computer, a tablet computer, a netbook computer, a personal computer (PC), a desktop computer, a personal digital assistant (PDA), a smart phone, or any programmable electronic device capable of communicating over a data connection to network  114 . In other embodiments, server  102  may represent server computing systems utilizing multiple computers as a server system, such as in a distributed computing environment. In general, server  102  is representative of any electronic devices or combinations of electronic devices capable of executing machine-readable program instructions and communicating with server  116  via network  114  and with various components and devices within data storage environment  100 . 
         [0012]    Server  102  includes persistent storage  108 . Persistent storage  108  may, for example, be a hard disk drive. Alternatively, or in addition to a magnetic hard disk drive, persistent storage  108  may include a solid state hard drive, a semiconductor storage device, read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, or any other computer-readable storage medium that is capable of storing program instructions or digital information. Volume  110  is stored in persistent storage  108 , which also includes operating system software, as well as software that enables server  102  to perform defragmentation processes, and communicate with server  116 , as well as other computing devices over a data connection on network  114 . Volume  110  and mirroring software  112  are stored in persistent storage  108 . Volume  110  contains all the data stored on the logical drive. In the context of computer operating systems, a volume, also referred to as a logical drive, is a single accessible storage area with a single file system, typically, though not necessarily, resident on a single partition of a hard disk. Mirroring software  112  enables server  102  to mirror data written or updated on volume  110  to mirrored volume  124  on persistent storage  122  in server  116 . 
         [0013]    In  FIG. 1 , network  114  is shown as the interconnecting fabric between data protection server  102  and server  116 . In practice, network  114  may be any viable data transport network. Network  114  can be, for example, a local area network (LAN), a wide area network (WAN) such as the Internet, or a combination of the two, and can include wired, wireless, or fiber optic connections. In general, network  114  can be any combination of connections and protocols that will support communications between data protection server  102  and server  116  in accordance with an embodiment of the invention. 
         [0014]    Data storage environment  100  also includes server  116 . Server  116  includes RAM  118 , central processing unit  120 , and persistent storage  122 . In various embodiments of the present invention, server  116  can each respectively be a laptop computer, tablet computer, netbook computer, personal computer (PC), a desktop computer, a personal digital assistant (PDA), a smart phone, or any programmable electronic device capable of communicating with server  102  via network  114 . Persistent storage  122  includes mirrored volume  124  and defrag software  126 . Mirrored volume  124  is a logical representation of volume  110  on persistent storage  108  of server  102 . Defrag software  126  enables server  116  to perform defragmentation operations on persistent storage  122  and volume  110  on persistent storage  108  in server  102 . 
         [0015]      FIG. 2  is a flowchart, generally designated  200 , depicting operational steps of defrag operation, on a mirrored volume within the data storage environment of  FIG. 1 , in an embodiment in accordance with the present invention. In an example embodiment, defrag software  126  performs a defrag operation on a secondary volume, also referred to as mirrored volume  124 , by suspending mirroring of synchronous volumes (that is, primary volume  110  and mirrored volume  124 , as depicted in step  202 . The mirroring of synchronous volumes is suspended when updates to the primary volume are no longer sent to the secondary volume. In other example embodiments, the defrag operation may begin on the primary volume (e.g., volume  110 ), and all track updates, as discussed in step  210 , would be sent to, and recorded, on the secondary volume (e.g., mirrored volume  124 ). 
         [0016]    In step  204 , defrag software  126  enables change recording on the primary volume, also referred to as volume  110 , to track all writes and/or updates to the primary volume. Change recording is a process of tracking any writes and/or updates to the data stored in a volume. In the example embodiment, defrag software  126  enables the change recording on server  102  after minoring is suspended between volume  110  and mirrored volume  124 . In other example embodiments, the change records, also referred to as track updates, may be stored on server  116  or another computing device on network  114  while the defragmentation process is running on mirrored volume  124 . 
         [0017]    Defrag software  126  then begins a DEFRAG operation with multiple pass logic on volume  124  as depicted in step  206 . Multiple pass logic in a disk defrag uses a recursive approach where file fragments are moved as needed to free the necessary space to write an entire defragmented file. The defragmentation process restarts once it reaches the end of the disk, and repeats until there are no more files to move. The result is an operation that requires fewer CPU cycles and memory, but is slower because the file fragments need to be moved several times. In other example embodiments, the defrag software  126  may use single pass logic on volume  124 . In a single pass defrag, the HDD is analyzed and a “virtual cluster map” is created of the defragmented HDD. If a defragmentation is required, the defragmentation process will recreate intermediate steps in order to accommodate the new files. The result is an operation that requires more memory and CPU cycles but might be faster and able to work with less free space or a higher fragmentation ratio. 
         [0018]    In step  208 , defrag software  126  serializes volume  110  on server  102  with volume  124  on server  116 . Serializing volume  110  prevents any updates from occurring on either volume while volume  110  is being serialized with mirrored volume  124 . When the volumes are serialized, both volume  110  and mirrored volume  124  are locked, or exclusively reserved, to prevent applications or processes from reading/writing to the disks. During the serialization process, the information in a volume table of contents (VTOC) is updated regarding the track layout of mirrored volume  124 . A VTOC is a data structure that provides a way of locating the data sets that reside on a particular disk volume. It can reside within the first 64K tracks on the volume, and lists the names of each data set on the volume as well as size, location, and permissions. Additionally, it contains an entry for every area of contiguous free space on the volume. Because mirroring has been suspended, the tracks on mirrored volume  124  are now in a different location than they are on the suspended primary volume (i.e., volume  110 ). As such, defrag software  126  needs to keep a before and after mapping of each track location as it changes throughout the defragmentation process. When the defragmentation process is complete, the data sets on the primary system are serialized using standard data set lock via exclusive enqueues (ENQs) along with the VTOC on the volume. The data set lock occurs when the hardware (i.e., volume  110  and volume  124 ) is reserved exclusively for the enqueue (i.e., writes to the hard disk). This ensures that no users will have outdated control block information with obsolete track locations. 
         [0019]    When the defrag operation is completed on mirrored volume  124 , defrag software  126  applies the track updates from volume  110  to the new location on mirrored volume  124  using relocation mapping as depicted in step  210 . At this point, the tracks that had been updated on volume  110  after the mirror was suspended are now applied to the defragmented mirrored volume  124 . The tracks are applied to the new location using the before and after mapping to ensure they are relocated or placed at the updated location. In other example embodiments, the track updates on server  102  for volume  110  may be mirrored across to server  116  in real-time to speed up the defragmentation process. 
         [0020]    In step  212 , defrag software  126  performs a hyperswap process for volume  110  and mirrored volume  124 . Upon applying the track updates to the defragmented mirrored volume  124 , a hyperswap process takes place for only those volumes involved in the defragmentation process. A hyperswap process switches the order of the primary and secondary volumes for applications and/or processes using the logical volume. When a hyperswap occurs, the applications and/or processes access the secondary volume for read and write operations as if the secondary volume were the primary volume. Stated another way, a hyperswap reverses the mirroring direction of the primary and secondary volumes such that, upon the performance of the hyperswap, the secondary volume mirrors updates to the primary volume. In other example embodiments, the hyperswap process may be performed across multiple servers in data storage environment  100 . 
         [0021]    Defrag software  126  then resynchs the change updates from the defragmentation process and applies application updates to volume  110  as depicted in step  214 . The resynchronization is driven by merging the change recording bitmaps from both volumes. The change recording bitmaps are the before and after track locations of the pending updates to volume  110  during the defragmentation process. The resynchronization causes changes to be updated back to the original primary volume  110 . When the resynch process completes, both volumes are substantially identical. 
         [0022]    In step  216 , defrag software  126  then performs a second hyperswap process for volume  124  and volume  110 . The second hyperswap process places volume  110  and mirrored volume  124  back in their original positions (i.e., volume  110  is now the primary volume and mirrored volume  124  is the secondary volume again) and state prior to when the defragmentation process began. In other example embodiments, the final hyperswap process may not be performed, leaving the volumes in the swapped state. In these embodiments, the volumes might only be swapped when a defragmentation process on the mirrored volumes completes. 
         [0023]      FIG. 3  depicts a block diagram, generally designated  300 , of components of the server computer executing the defrag operation, in an embodiment in accordance with the present invention. It should be appreciated that  FIG. 3  provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environment may be made. 
         [0024]    Server  300  includes communications fabric  302 , which provides communications between computer processor(s)  304 , memory  306 , persistent storage  308 , communications unit  310 , and input/output (I/O) interface(s)  312 . Communications fabric  302  can be implemented with any architecture designed for passing data and/or control information between processors (such as microprocessors, communications and network processors, etc.), system memory, peripheral devices, and any other hardware components within a system. For example, communications fabric  302  can be implemented with one or more buses. 
         [0025]    Memory  306  and persistent storage  308  are computer readable storage media. In this embodiment, memory  306  includes random access memory (RAM)  314  and cache memory  316 . In general, memory  306  can include any suitable volatile or non-volatile computer readable storage media. 
         [0026]    Mirrored volume  322  and defrag software  324  are stored in persistent storage  308  for execution and/or access by one or more of the respective computer processors  304  via one or more memories of memory  306 . In this embodiment, persistent storage  308  includes a magnetic hard disk drive. Alternatively, or in addition to a magnetic hard disk drive, persistent storage  308  can include a solid state hard drive, a semiconductor storage device, read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, or any other computer readable storage media that is capable of storing program instructions or digital information. 
         [0027]    The media used by persistent storage  308  may also be removable. For example, a removable hard drive may be used for persistent storage  308 . Other examples include optical and magnetic disks, thumb drives, and smart cards that are inserted into a drive for transfer onto another computer readable storage medium that is also part of persistent storage  308 . 
         [0028]    Communications unit  310 , in these examples, provides for communications with other data processing systems or devices, including resources of network  114  and server  116 . In these examples, communications unit  310  includes one or more network interface cards. Communications unit  310  may provide communications through the use of either or both physical and wireless communications links. Mirrored volume  322  and defrag software  324  may be downloaded to persistent storage  308  through communications unit  310 . 
         [0029]    I/O interface(s)  312  allows for input and output of data with other devices that may be connected to server  102 . For example, I/O interface  312  may provide a connection to external devices  318  such as a keyboard, keypad, a touch screen, and/or some other suitable input device. External devices  318  can also include portable computer readable storage media such as, for example, thumb drives, portable optical or magnetic disks, and memory cards. Software and data used to practice embodiments of the present invention, e.g., mirrored volume  322  and defrag software  324 , can be stored on such portable computer readable storage media and can be loaded onto persistent storage  308  via I/O interface(s)  312 . I/O interface(s)  312  also connect to a display  320 . 
         [0030]    Display  320  provides a mechanism to display data to a user and may be, for example, a computer monitor. 
         [0031]    The programs described herein are identified based upon the application for which they are implemented in a specific embodiment of the invention. However, it should be appreciated that any particular program nomenclature herein is used merely for convenience, and thus the invention should not be limited to use solely in any specific application identified and/or implied by such nomenclature. 
         [0032]    The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
         [0033]    The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
         [0034]    Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
         [0035]    Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
         [0036]    Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
         [0037]    These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
         [0038]    The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0039]    The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.