What does RAID stand for?

qazxswedc

In some books it's (redundant array of independent disks) and in others its (redundant array of inexpensive disks) which one is it. I dont know maybe it's both. i'm just curious b/c one time i was doing some "Measure Up" practice exams and the question was what RAID stood for, and (redundant array of independant disks) was concidered wrong.
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Webmaster

I've seen both used equally as often over the past 12 years. Actually, in my Network+ TechNotes I wrote:

"RAID stands for Redundant Array of Inexpensive (or Independent) Disks"

So pick the one you like best and forget about Measure Up's questions as you certainly won't have to choose between Inexpensive and Independent on any actual exam.

supertechCETma

"The original acronym RAID stood for Redundant Array of Inexpensive Disks. UC Berkeley researchers introduced the concept in 1988. RAID was proposed as a solution to the then lagging performance of data storage. In the original proposal. a disk array would use several low cost, low capacity drives. At the time, the average MTBF (mean time between failure) for the array was less than the time for a single disk. This shortcoming was conquered by storing redundant data or parity data, which allowd continued data access or even data reconstruction in the event of disk failure." (Lister, p.552, 2004)

Lister, G. (2004). The Small Computer System Interface, SCSI. A+ 4 Real. GA. Suwanee. StudyExam4Less Expert Series

rbowman

I believe that the "I" in RAID is for Inexpensive because its true that the disc was inexpensive. You cannot say independant because in RAID 5 you need at least 3 discs and this is for the parity info to be spread across multiple drives so that they may rebuild one another if 1 or multiple disc fail. In other words, if one fails it RELIES on the other discs and software to rebuild the failed disc.

In the early days of RAID you could almost say independant due to RAID 1 just having redundancy by either have 2 disc connected to 1 disc controller or 2 disc controllers and 2 discs. The latter is known as duplexing.

RussS

Going back to when the term was coined ..... check the price of SCSI disks

supertechCETma

RussS wrote:

Going back to when the term was coined ..... check the price of SCSI disks

be that as it may...

"History
Back in the middle eighties SLED:s (Single Large Expensive Disk) were the most popular
media for storing data. At that time, the disk drives did not by far have the storing capacity or
the performance that disks have today. To be able to provide a large amount of data one had
to have lots of disk drives, which all had to be mounted in a single file tree2. This was an
extremely messy and inconvenient way of handling data. Disks these days were also very
expensive, hence the meaning of SLED. Another big problem was, and still is, loss of data
because of disk failure. A solution for this was much needed.
3To take care of these problems IBM co-sponsored Berkeley University of California to build
a disk array subsystem to which IBM had received a patent in 19784. In 1987 Randy Katz and
Dave Patterson, both working at Berkeley University of California, had succeeded. They
called the solution RAID5. RAID stand for “Redundant Array of Inexpensive Disks”,
although some people chose to change “… Inexpensive …”, which is the original word, to
“… Independent …”. Randy and Dave clustered multiple smaller and less expensive disks
into an array. By doing this, all disks appear to the rest of the world as if there was just one
single large disk. The result was compared to SLED:s according to cost versus performance.
It turned out to that RAID had the same or superior performance as SLED, but with a
theoretical Meantime Before Data Loss (MTBDL) that was reduced to an acceptable level. (Persson, Evertsson, 2002)

Persson, J., Evertsson, G. (2002). RAID Systems. Blekinge Institute of Technology, Sweden. Retrieved May 30, 2006 from http://www.guzzzt.com/files/coding/raid.pdf

OpenSource

Although the word "Independent" is not technically correct for versions of RAID such as RAID-5, I believe the word "Independent" works better then the word "Inexpensive". Why? Well, mainly because "Independent" better describes the concept of RAID then "Inexpensive" and because "Inexpensive" is too broad a word for current day RAID technology...

Think of it this way, I can get away setting up a RAID array of 10GB IDE/ATA hard drives from a swap meet that I purchased for say $10 (total) or even old spare drives in my closet, hence "Inexpensive"... Or, I can setup a RAID array of 10,000RPM SCSI drives for $800+ (per drive), which is anything by "Inexpensive".

Just my thoughts...

- Joey

raied

Both are correct - you can use either independent or inexpensive.

plettner

Inexpenive is the term I always used. To be honest, I don't think I've heard independent discs used.

TheShadow

RAID was originally invented for mainframes and Mini's where an $800 or even $8,000 drive was ridiculously Inexpensive. I implemented a RAID array and helped design a controller in the early 80's. A PC could not have handled it back then but now changing the word to Independent seems more appropriate.

TheShadow

Hmmm while Katz and Peterson did create RAID5, I believe the term RAID itself was coined much earlier than 1987. There were other raid levels in existance as everyone was investigating the technology at the same time. Jai Menon at IBM, Dan Hillis at um um Thinking Machines maybe, also there was work at DEC and Burroughs. RAID5 however became pretty much the standard for cost versus performance. I think that Menon and team members made the first commercial protype but I could be wrong.

Alien

I've always known it as "Redundant Array of Inexpensive Drives". Some terms have varying words from various sources like the PCMCIA.

TheShadow

People Can't Memorize Computer Industry Acronyms.

BubbaJ

They could do the same that as DVD. Different parties had different definitions of what it stood for so the standards committee officially made it stand for nothing; it is just DVD.

plettner

People Can't Memorize Computer Industry Acronyms.

Exactly right!!!

I'm studying through the Server+ book (the CompTIA/ILT publication) and even they mention some of the acronyms that are confused by people (which I've forgotten!!! - I gotta study harder).

Slowhand

I think the term RAID is one of those acronyms that has come to mean a word, unto itself, and we really don't think about the actual words it stands for anymore. (Hence, the reason we can't remember what the I stands for, anymore.) I've had this debate about RAID, about SCSI, and any other number of acronyms. I look at it this way: as long as I know what the technology the acronym stands for is, I'm perfectly content. (When I'm tested, I'll go with whatever the official traning material says, when I'm asked, I'll go with whatever meaning I looked up last.)

And yes. . . I'm a lazy, lazy techie. :P

Danman32

One COULD concievably use Independent for 'I' in RAID since the disks are independent in the sense if one fails, the rest can still provide data while the failed disk is replaced.
I just realized that some RAID levels aren't really RAID, but rather 'AID', as they are missing the Redundancy that 'R' represents.

As for drives being 'inexpensive', my first HD cost me $800 for a 20 MB Seagate MFM drive. 2 or 3 years later, I bought a replacement for $400. By some fanagaling, I got both to work for a whopping 40 MB!
Later I inhereted an 80 MB full height drive, I call the 'door stopper' that uses the same MFM technology. I still have that drive. I have no idea if the data on it is still any good. Maybe I'll fire up that old machine.