Illinois Administrative Code › Title 44 - GOVERNMENT CONTRACTS, GRANTMAKING, PROCUREMENT AND PROPERTY MANAGEMENT › Part 4500 - LOCAL RECORDS COMMISSION OF COOK COUNTY › Appendix B - Reliable Storage Media for Electronic Records - A Guide for Government Agencies

Current through Register Vol. 48, No. 28, July 12, 2024
Modern computer systems use a wide variety of storage media to
				store and access electronic data. What media is used depends on a number of
				factors, but cost, speed of access and ease of use are common drivers of
				selection decisions. Often overlooked are concerns of long-term reliability and
				sustainability. Electronic records are vulnerable to degradation or loss if not
				maintained in an appropriate storage environment which takes into consideration
				media reliability and guards against technological obsolescence.
To say that media is reliable is to indicate that it can be
				trusted to preserve and provide access to data stored on it over time. While no
				storage medium can guarantee reliability and sustainability, certain media
				formats have distinct advantages over others in this regard. Understanding a
				media format's strengths, weaknesses and expected life span allows IT managers
				to appropriately protect the data stored on that media.
No storage media alone can ensure the preservation of
				electronic records. Selecting appropriate media is one part of a greater
				preservation strategy which includes using sustainable file formats, actively
				managing files over time, planning for future technology change and securing
				adequate resources to support preservation activities.
The following factors should play a part in the selection of
				any storage media for electronic records.
Durability: Durability is a factor representing the
				ability of electronic storage media to withstand wear and environmental
				conditions. Corruption (data rot) can occur as the electrical charge, magnetic
				orientation, or physical material degrades, causing unintended changes or loss
				of data.
Assessing Durability: Durability of media is
				commonly expressed in terms of "mean time between failures," which indicates
				how long a given drive/tape/disk can be expected to operate before
				failure.
Widespread Adoption and Use: Widespread adoption and
				use is a factor indicating a wide user base, meaning more stakeholders have a
				vested interest in keeping the storage media viable and well-supported.
				Widespread adoption also serves as an indicator of general media stability and
				generally provides a lower overall lifecycle cost of storage. The more widely a
				storage medium is used, the more likely it is to have long-term support to
				maintain it. Widely adopted technologies are typically documented and based on
				open standards supported by multiple hardware vendors. This reduces the chance
				of a medium becoming inaccessible due to one vendor going out of
				business.
Assessing Adoption and Use: While there is no
				universal benchmark that indicates something is "widely used" one should look
				for examples of a given technology being used by other institutions, government
				agencies and private corporations. Multiple manufacturers and distribution
				sources are also good indicators of a widely-used technology.
Integrity: Integrity is a factor indicating the
				ability of electronic storage media to protect against and correct data
				corruption. The use of parity bits, error correcting codes, checksum
				algorithms, physical and digital access controls, and other measures help
				ensure that data is not corrupted. The media format used and how data is stored
				on it determines which of these measures can be applied. Compressed,
				de-duplicated, or encrypted data is more susceptible to corruption as
				non-functional software or an uncorrectable error can make a large amount of
				data unreadable.
Assessing Integrity: All storage media have listed
				specifications that indicate what types of integrity protection are possible,
				but one must also consider the source. New technologies frequently come with
				lofty manufacturer claims which should be considered critically until
				independently verified through outside testing or use.
Redundancy: Redundancy is a factor that indicates
				the data stored on electronic storage media is being replicated to ensure
				recovery of data in the event of a data loss incident. A minimum of one
				additional copy of any data representing electronic records must be maintained
				to protect against such a loss. At least one copy should be stored in a
				geographically separate location. Depending upon cost and performance needs,
				multiple types of storage may be used, such as a hard drive for the primary
				copy and magnetic tape for the backup copy.
Assessing Redundancy: Redundancy can be assessed by
				determining if you have one additional copy in a geographically separate
				location. IT policies should ensure that all electronically stored data will be
				restorable in the case of total loss of the primary storage environment.
The following is a list and descriptions of storage media
				formats currently recommended by the Illinois State Archives for use in storing
				electronic records.
Format
Short term
Long term
Do Not Use
HDD
X
X
SSD (Internal)
X
X
Magnetic Tape
X
X
Cloud Storage
X
X
Optical (All Types)
X
USB Flash
X
Obsolete media
X
STORAGE MEDIA
LONG-TERM RETENTION
The following formats are considered acceptable choices for the
				retention of records greater than a decade.
Magnetic Tape:
A durable recording medium which uses a plastic film
				coated with magnetic material to record information, magnetic tape has been
				used to record computer data since the 1950s. Early formats of this medium
				consisted of open reel tapes, but modern varieties all use a cartridge of some
				sort.
The most widely used current version is LTO (Linear
				Tape-Open), which is based on open standards, as opposed to several proprietary
				competitors. LTO is currently in its 6th generation, with LTO-6 introduced in
				2012. LTO-6 tapes have an uncompressed storage capacity of 2.5 Terabytes (TB).
				A number of different companies currently manufacture LTO tapes and drives, and
				LTO technology now accounts for close to 90% of the data tape market. LTO
				drives have some backwards compatibility, being able to read tape from two
				generations past and write to tape one generation past (an LTO-6 drive can read
				LTO-4, 5 and 6, and write to 5 or 6). Older versions of LTO tapes can remain
				viable for a few decades so long as users possess the appropriate drive, but it
				is best to migrate to newer versions every two generations to avoid potential
				loss of access.
Other current tape technologies are the Oracle
				Storagetek T1000X series and IBM TS1140 line. Both offer higher capacities and
				faster transfer speeds than LTO, but at a higher cost per GB. They are both
				proprietary formats, with drives and automated libraries available only from
				Oracle and IBM, respectively. Both companies are long-established and stable,
				but if either chooses to discontinue their tape technologies users will have no
				choice but to switch formats entirely. LTO thus remains the safer choice in
				terms of adoption and support.
Pros of magnetic tape:
Durability up to 30 years (best practice migration
				in 8-12 years)
High capacity, low cost compared to other storage
				technologies
Widely used, mature technology
High transfer rates, low error rates
Low energy consumption
Cons of magnetic tape:
Slow access time (average 50 seconds)
Wears out faster with frequent access
Hard Disk Drive (HDD):
Hard disk drives store data on a stack of rapidly
				spinning metal disks coated in magnetic material. HDDs have been used for
				primary storage in computers since the early 1960s, and are used in the vast
				majority of personal computers and servers today. They can be internally
				mounted or connected externally. For stability and monitoring it is recommended
				that only internal HDDs be used for long-term records storage, with external
				drives being used for file transport or backup duties only. Due to their
				extensive use HDDs are inexpensive, and are available from a wide variety of
				manufacturers. They can be prone to unexpected failures, however, so active
				monitoring, regular media refreshment and appropriate backups must be used to
				ensure the safety of the records stored within.
To help manage the inherent risks associated with
				HDD technology a RAID (Redundant Array of Independent Disks) setup should be
				used. RAID uses a battery of drives that are interlinked and automatically
				duplicate data across the drives, thus protecting content from loss. There are
				different levels of RAID which correspond to greater or lesser amounts of
				duplication, but for records preservation RAID 6 or 10 are recommended. Both
				involve high levels of fault tolerance, meaning one or more drives in the array
				could fail at once with no irretrievable loss of data.
Pros of HDD:
Rapid access to content
High capacity, low initial cost
Widely used, mature technology
Easily scalable through networking
Cons of HDD:
Short life span (average 4-6 years, best practice
				migration in 3-5 years)
High energy consumption
Expensive for large-scale applications or for
				long-term content
Higher error rate than tape
Solid State Drive (SSD):
A flash memory storage device first developed in the
				mid-1990s with no moving parts that typically uses the same shape, interface,
				and power source as standard hard drives. Data is stored in static electronic
				chips rather than on magnetized spinning platters. This results in much shorter
				time required for drive start-up, read, random access, latency and data
				transfer as well as reduced energy use, but at a cost up to ten times that of
				standard hard drives. As the price continues to drop in the coming ten to
				twenty years, solid state drives are expected to replace standard hard drives
				as the primary storage medium for laptops, desktops, servers, mobile devices,
				and external storage.
Pros of SSD:
Resilient to physical shock
Lower failure rate compared to standard hard
				drives
Fast access time (<0.1 ms)
Low energy consumption
Cons of SSD:
High cost compared to other storage
				technologies
Limited lifetime due to limited number of times a
				storage block can be written
Susceptible to data loss due to power outages or
				long-term unpowered storage
Maturing technology with most commercial
				availability beginning in 2007
Cloud Storage:
"Cloud storage" refers not to a particular type of
				media, but a method for managing data using networked storage providers. Cloud
				hosting companies provide technical infrastructure which often spans across
				many geographical areas, providing high levels of redundancy and remote access
				for customers. While not a new concept, commercial cloud storage has only seen
				widespread adoption by both private and public entities in the last decade.
				There are many cloud service providers but much of the commercial market is
				dominated by companies like Amazon, Microsoft and Google. Cloud storage
				services can range from bare-bones warehousing with minimal security and upkeep
				to highly customized management of data, with integrity checks, enhanced
				security and faster access speeds.
Cloud storage in general has shown itself to be very
				reliable regarding the preservation of data. Nonetheless, greater concerns
				arise surrounding the protection of that data from inappropriate access. Data
				breaches can and do happen, and network security must be a primary focus for
				any agency wishing to use cloud storage for their records. Only established
				providers with proven track records should be used, but they do not necessarily
				need to be one of the large corporate entities. Many smaller cloud providers
				actually use one of the large hosts, and simply add their own layers of
				services on top of the bare storage. Cloud storage providers may not
				automatically provide long-term preservation services such as fixity checks,
				audit logging or creation of additional metadata, so agencies must still plan
				on performing these tasks themselves or specifically contracting cloud
				providers to do so.
Pros of cloud storage:
Highest level of duplication and geographic
				redundancy
Easy access from multiple locations
Keeps up with technology trends without additional
				investment
Trades unpredictable maintenance costs for known
				subscription fee
Can be cheaper than investing in own
				technology
Cons of cloud storage:
Relatively higher risk of security breach
Laws may prevent the storage of certain types of
				sensitive data in the cloud
Some providers may not be reliable or may go out of
				business
Less control over data / loss of physical
				custody
SHORT-TERM RETENTION (10 years or less)
The following formats are inappropriate for the long-term
				storage of electronic records, but may be used for short-term storage of
				records.
Optical Media:
A thin, circular, plastic disc with a reflective
				layer upon which data is stored in the form of pits and lands. The reflective
				layer typically resides on the label side of the disc facing inward although
				double-sided and dual-layer discs are also available. It can be engraved
				(read-only), dye-based (write-once), or alloy-based (rewritable). A laser is
				used to read data from the spinning disc based on changes in the reflection
				caused by the pits and lands. Several forms of optical media are widely adopted
				and supported; descriptions of the most common forms are provided below.
				Optical media is subject to damage due to scratches or breakdown of the
				recording dye, although proper storage and handling, regular migration to new
				media, and use of a gold reflective layer can mitigate these risks. Many types
				of writable optical media also use volatile organic dyes to store information,
				and can degrade over time. As cloud and network-based storage become common,
				optical media usage is expected to decline.
CD: The Compact Disc was originally developed in the
				early 1980s, evolving from the older LaserDisc format, and it is still widely
				supported. A standard CD is 4.7 inches in diameter and can hold up to 80
				minutes of audio or 700 MB of data, although smaller and non-round shapes also
				exist. The most popular CD formats include CD-ROM (read-only), CD-R (write
				once), and CD-RW (rewritable). Both the drives and recordable media are speed
				rated, indicated as a multiplier of 1x (1200 Kbps). The writing speed as set by
				the recording software should not exceed the rated speed of the recording media
				to prevent data corruption. The CD format includes strong error correction
				coding to prevent data loss due to scratches, fingerprints, or other
				environmental contaminants. CDs suffer from low capacity compared to other
				modern storage technologies.
DVD: The Digital Versatile Disc was developed in
				1995. The DVD uses the same dimensions as a CD but offers a standard capacity
				of 4.7 GB or
				8.5 GB for dual
				layer formats. Most DVD players can also read CDs. The most popular DVD formats
				include DVD-ROM (read-only), DVD-R and DVD+R (write once), and DVD-RW and
				DVD+RW (rewritable). The plus and minus formats require different recording
				media and drives to write. Most DVD players can read all DVD and CD formats
				while some can also write in all formats. Similar to CDs, both the DVD drives
				and recordable media are speed rated, indicated as a multiplier of 1x (10.5
				Mbps). The writing speed as set by the recording software should not exceed the
				rated speed of the recording media to prevent data corruption. The DVD format
				also includes strong error correction coding to prevent data loss due to
				scratches, fingerprints, or other environmental contaminants. DVDs should not
				be used for long-term data storage, because their reliability over time has not
				yet been adequately demonstrated.
Blu-ray: The Blu-ray Disc was developed in 2006.
				Blu-ray uses the same dimensions as a CD and DVD but offers a standard capacity
				of 25 GB or 50 GB for dual layer formats. Most Blu-ray players can also read
				CDs and DVDs. The most popular Blu-ray formats include BD-ROM (read-only), BD-R
				(write once), and BD-RE (rewritable). Similar to DVDs, both the Blu-ray drives
				and recordable media are speed rated, indicated as a multiplier of 1x (36
				Mbps). The writing speed as set by the recording software should not exceed the
				rated speed of the recording media to prevent data corruption. The Blu-ray
				format also includes strong error correction coding to prevent data loss due to
				scratches, fingerprints, or other environmental contaminants. Like DVD, Blu-ray
				discs have not been adequately evaluated for long-term stability.
M-Disc (Millenial Disc): A relatively new player on
				the optical front, M-Disc technology has only been available since 2009, and
				has yet to see wide-spread adoption. M-Discs use a proprietary "stone-like"
				material in the storage layer, sandwiched between plastic discs. Currently both
				DVD and Blu-ray variants are available, with capacities similar to standard
				varieties of those discs. Special M-Disc drives are required to write data to
				the discs, but standard DVD or Blu-ray drives are able to read data from them.
				Millenniata, the company behind the format, claims such discs have a projected
				lifespan of 1000 years. Independent stress tests have shown that M-discs are
				indeed more resistant to environmental degradation than traditional varieties,
				but the life span statement cannot be corroborated. Even if such claims are
				accurate, optical drives are already losing ground to newer storage
				technologies, and will likely be rendered completely obsolete within decades.
				It is possible that M-Disc technology will be much more widely adopted in the
				future, but at this juncture it is too limited to consider as a long-term
				storage option.
Pros of optical media:
Convenient and portable
Widely supported formats available
Low energy consumption in storage
Cons of optical media:
Not well-suited for frequent writing or for fast
				read access from multiple discs
Limited capacity per disc compared to other modern
				storage
Widely varying lifetime depending on use and
				care
Aging technology being slowly replaced by flash
				media and cloud storage
DO NOT USE
The following formats should not be used for the short-term or
				long-term storage of electronic records. If records are currently stored on
				such media they should be migrated onto appropriate media to avoid their
				permanent loss.
USB Flash Drive:
A rewritable portable data storage device developed
				in 2000 with no moving parts that connects to a computer using the Universal
				Serial Bus interface. Data is stored electrically in chips using power from the
				USB interface itself. USB flash drives offer many of the same performance
				benefits and limitations as Solid State Drives but typically have a smaller
				capacity. USB flash drives come in a variety of shapes and sizes from standard
				three inch "stick" to novelty shapes and even some barely larger than the USB
				plug. USB flash drives quickly displaced floppy disks as the preferred means to
				quickly write and transport data but may themselves be displaced as cloud and
				network-based storage become common. These portable devices are useful for
				short-term information sharing, but are far too easily lost or compromised to
				serve as reliable storage for electronic records.
Pros of flash drives:
Convenient
Durable
Widely supported
Fast transfer rate (up to 5 Gbps with USB 3.0
				)
Low energy consumption
Cons of flash drives:
Easily misplaced or stolen
Limited write protection
Limited lifetime due to limited number of times a
				storage block can be written
Older Magnetic Tape Formats:
Due to lack of support for obsolete technology,
				agencies should avoid any tape formats which have been discontinued. Caution
				should also be exercised when using older variants of current tape technology
				such as LTO-1 or LTO-2, as backward compatibility of LTO technology only goes
				back two generations. Any records currently stored on older formats such as
				these should be migrated forward to more current versions to ensure continued
				accessibility.
Any Size Floppy, ZIP, JAZ Disk:
A wide array of magnetic diskette technologies have
				now been almost completely abandoned in favor of more current storage options.
				Even if still technically usable, such disks should not be used for storage of
				electronic records.
ADDITIONAL RESOURCES
Best practices for a digital storage infrastructure for the
				long-term preservation of digital files (Digitizing Contemporary Art)
Best Practices for Media Selection and Migration (University of
				Illinois)
Selecting Storage Media for Long-Term Preservation (UK National
				Archives)
FAQ about Optical Storage Media (National
				Archives)