Everybody understands physical storage, but when it comes to digital storage, things can get a little complicated.
This is only at first glance, however, as digital storage isn’t all that different from the bookshelves in your office or the cabinets in your kitchen.
To clear the air, here’s everything you need to know about storage technology.
If you’re researching storage types, you’re likely to come across SAN, DAS, and NAS. As with most acronyms, these are indecipherable unless you know what they stand for, so let’s fix that.
DAS (direct attached storage) is a form of digital storage that, as its title suggests, is directly attached to the computer that is attempting to access it. Unlike SAN storage, there’s no network involved. DAS storage could be a hard drive, a CD, or an SD card.
DAS is a block device from a disk which is physically [directly] attached to the host machine.
• You must place a filesystem upon it before it can be used.
• Technologies to do this include IDE, SCSI, SATA, etc.
SAN (storage area network) is a high-speed network that provides storage at block-level network access. In other words, it uses switches, hosts, and storage devices that are connected, as opposed to being from a single source.
SAN is a block device which is delivered over the network.
• Like DAS you must still place a filesystem upon it before it can used.
• Technologies to do this include FibreChannel, iSCSI, FoE, etc.
NAS (network attached storage) is a storage technology that exists on a server that’s connected to a network. Like SAN, they operate over a network, but the difference is that NAS storage is all coming from a single device. SAN storage is a network of devices.
NAS is a filesystem delivered over the network.
• It is ready to mount and use.
• Technologies to do this include NFS, CIFS, AFS, etc
Storing data physically can be scary because you never know if there will be a fire, a flood, or if something could simply get lost. Digital storage fixes this problem, but there’s still the possibility that you could lose files by way of an accident or malfunction.
RAID works by placing data on multiple disks and allowing input/output (I/O) operations to overlap in a balanced way, improving performance. Because the use of multiple disks increases the mean time between failures (MTBF), storing data redundantly also increases fault tolerance.
RAID arrays appear to the operating system (OS) as a single logical hard disk. RAID employs the techniques of disk mirroring or disk striping. Mirroring copies identical data onto more than one drive. Striping partitions each drive's storage space into units ranging from a sector (512 bytes) up to several megabytes. The stripes of all the disks are interleaved and addressed in order.
RAID 0: This configuration has striping, but no redundancy of data. It offers the best performance, but no fault tolerance.
RAID 1: Also known as disk mirroring, this configuration consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage.
RAID 5: This level is based on block-level striping with parity. The parity information is striped across each drive, allowing the array to function even if one drive were to fail. The array's architecture allows read and write operations to span multiple drives. This results in performance that is usually better than that of a single drive, but not as high as that of a RAID 0 array. RAID 5 requires at least three disks, but it is often recommended to use at least five disks for performance reasons.
RAID 6: This technique is similar to RAID 5, but includes a second parity scheme that is distributed across the drives in the array. The use of additional parity allows the array to continue to function even if two disks fail simultaneously.
RAID 10 (RAID 1+0): Combining RAID 1 and RAID 0, this level is often referred to as RAID 10, which offers higher performance than RAID 1, but at a much higher cost. In RAID 1+0, the data is mirrored and the mirrors are striped.
RAID 01 (RAID 0+1): RAID 0+1 is similar to RAID 1+0, except the data organization method is slightly different. Rather than creating a mirror and then striping the mirror, RAID 0+1 creates a stripe set and then mirrors the stripe set.
RAID 50 (RAID 5+0): This configuration combines RAID 5 distributed parity with RAID 0 striping to improve RAID 5 performance without reducing data protection.
As with everything else, storage is quickly becoming exclusively digitized. However, that’s something of a blanket statement, because there are multiple forms of storage technology.
Depending on your purpose, you may be interested in SAN storage over DAS storage, or vice-versa. Or maybe NAS storage is more suitable to your unique needs.
SAN will disperse your data across a network, while NAS will consolidate your data to a single location, but still be active on a network. DAS, on the other hand, runs without a network and is accessible natively through your computer—perfect for areas without internet access.
For the more safety-oriented, RAID is the best option. It takes multiple steps to ensure your data always remains safe by copying it and spreading it across multiple platforms. Even if one file gets corrupted, you’re always going to have more.
Whichever form of storage technology you choose, it definitely beats dedicating a quarter of your office space to file cabinets.