Network-Attached Storage (NAS) is dedicated data storage technology that connects directly to a computer network, providing
centralized data access and storage. NAS systems typically combine redundant storage features such as RAID 5 configurations
with file-sharing ability across the network while not limiting file transfer protocols.
The type of file-sharing protocols used is one difference between NAS and the Storage Area Network (SAN) (see below), which typically uses proprietary protocols. However, unlike SAN, NAS has limited co-location ability, which means limited
redundancy among multiple storage servers. In a SAN system, these storage servers are mirrors of each other and contain the
same data; if one server goes down, another server can take over. NAS has less flexibility with mirroring multiple storage
servers. For a company that needs only one backup that everyone can use, a NAS system is appropriate. However, for a company
that requires multiple storage facilities to make sure data are available at all times, a SAN system would be more appropriate.
NAS is becoming popular in small businesses because of its low cost ($1,000 to $2,000) and small space requirement and because
it typically fits the data storage needs of these businesses.
STORAGE AREA NETWORK
SAN systems work a lot like direct attached storage systems; however, they are attached to the network rather than the server.
Multiple SAN units can be added to a network and can be located off-site to ensure data safety in case of fires, floods, or
other disasters in which only one part of the SAN is affected. Also, these units can be set to back up each other without
any human interaction, and these units provide minimal downtime if one site fails, provided the software is also co-located.
SANs also allow you to manage all your storage centrally and to back up continuously. However, the setup and maintenance of
these systems is expensive (tens of thousands of dollars), and SAN capabilities may be excessive for most veterinary hospitals.
RECORDABLE REMOVABLE MEDIA
Data backup on a writable media such as CDs or DVDs is an acceptable image storage method that is used primarily for disaster
recovery purposes. DVDs are the logical choice since they hold about seven times more data than CDs. The benefits of a removable
storage media backup (CD or DVD) are mobility, low-cost, and easy replication. Since CDs and DVDs are easy to replicate, a
copy can be kept both at the hospital and off-site in case of a disaster. In addition, CDs and DVDs are write-once media,
so they cannot be altered and thereby stand up to scrutiny in court.
When using a CD or DVD backup, someone must be responsible for maintaining and organizing the backup system. In many instances
this responsibility falls by the wayside and only becomes an issue after a disaster has occurred.
Magnetic tape can also be used as a writable media device similar to CDs or DVDs. Several types of tape backups are available,
and as with most technology, the more storage capacity you need, the greater the cost. These systems can be integrated into
a server or can be rack-mounted for large installations.
Magnetic tape has a large storage capacity and is easy to use, allowing you to plug it in, back it up, and forget it. Magnetic
tape storage also has a lower cost than digital storage. However, magnetic tape storage has slow data recovery migration,
at 15- to 30-second access per Mb or 0.067 Mbs (Mb per second) vs. CD or DVD technology, which usually starts at 36 Mbs.1 Also most magnetic tape systems allow data to be altered after the fact; thus, the information can be discredited in court.
The exception to this is the LTO Generation 3 WORM (Write Once Read Many) tape cartridges, which can only be written to once.
Also, since the tapes are magnetic, magnetic fields can damage the tape. In addition, heat can warp the tape. Tape storage
is a more viable option for systems that can tolerate recovery downtimes of several hours.
Zip (Iomega) drives can also be used as recordable and removable storage methods. Zip drives come in 250, 500, and 750 GB
sizes. They work like removable floppy disk drives but are sturdier than the older magnetic media. These drives are easy-to-use
and inexpensive and have a large storage capacity. However, these disks may be more suitable for temporary storage than for
permanent storage because of past problems with drive failures, although past performance issues do not indicate future performance