Slashdot Mirror
Raid 0: Blessing or hype?
Yoeri Lauwers writes "Tweakers.net investigates matters a bit more clearly and decides that AnandTech and Storagereview should think twice before they shout that "RAID 0 is useless on the desktop". Tweakers.net's tests illustrate the contrary"
Have you tried mount points in Windows? It's Disk Manager, right click on a drive and choose "Change Drive Letter or Paths..." - although it has to be an empty partition when you do this... It's just like linking drives to mount points in *nix.
"We know what happens to people who stay in the middle of the road. They get run over." - Aneurin Bevan
Just post the relevant Wiki information about Raid 0, dont need Raid's life history ;).
RAID 0
A RAID 0 Array (also known as a stripe set) splits data data evenly across two or more disks with no parity information for redundancy. RAID-0 is normally used to increase performance, although it is also a useful way to create a small number of large virtual disks out of a large number of small ones. Although RAID-0 was not specified in the original RAID paper, an idealized implementation of RAID-0 would split I/O operations into equal-sized blocks and spread them evenly across two disks. RAID-0 implementations with more than two disks are also possible, however the reliability of a given RAID-0 set is equal to the average reliability of each disk divided by the number of disks in the set. That is, reliability (MTBF) decreases linearly with the number of members - so a set of two disks is half as reliable as a single disk. The reason for this is that the file system is distributed across all disks. When a drive fails the file system cannot cope with such a large loss of data and coherency since the data is "striped" across all drives. Data can be recovered using special tools, however it will be incomplete and most likely corrupt.
RAID-0 is useful for setups such as large read-only NFS servers where mounting many disks is time-consuming or impossible and redundancy is irrelevant. Another use is where the number of disks is limited by the operating system. In Windows, the number of drive letters is limited to 24, so RAID-0 is a popular way to use more than this many disks. However, since there is no redundancy, yet data is shared between drives, hard drives cannot be swapped out as all disks are interdependant upon each other.
RAID 0 was not one of the original RAID levels.
Unlike other RAID-levels, RAID 0 does not offer protection against drive failure in any way, so it's not considered 'true' RAID by some (the 'R' in RAID stands for 'redundant', which does not apply to RAID-0).
When you have multiple hard drives, it's more likely that one will fail than if you just have one. For the obvious statistical reasons. Plus because of heat problems in many systems.
In a non-RAID setup with multiple hard drives, when one fails, you lose whatever was on that drive.
With RAID-n (for non-zero n), you lose nothing. You say "oh well", put in a spare drive, and send the old one back for replacement. (In the other order if you're cheap.) The array rebuilds itself. Without even shutting down the machine, if you have the hot-swappable drive cages.
With RAID-0, you lose everything on all of your hard drives.
RAID-0 is considerably less reliable than a single hard drive.
Since 2002, I have been using the SIIG Raid 0 http://www.siig.com/product.asp?pid=424 card on a 1999 Sawtooth G4 with 0.48TB of internal storage. Hardware-wise, this is an OEM Acard card; also available from Sonnet and Miglia.
_ RAID.html
No disk failures to date ---I backup weekly with Apple's Backup 2.0
Here are some benchmarks that compare software RAID 0 performance (included free with OS X) vs. hardware RAID 0: http://www.xlr8yourmac.com/OSX/OSX_RAIDvsIDE_Card
The next pasture is always greener
Here's the whole thing - I *have* tried it. If your workload involves lots of long, sequential reads, it's a great thing. I've personally got 2 machines running drives in RAID 0 as they get used for working with files in the 1.5-2GB range. It makes a difference here.
The whole point of SR and AT's articles, however, is that for most desktop systems, RAID 0 is pretty much a bad idea. You'll see marginal improvement on more random data sets, but you've spent four times as much, and, more importantly in my mind, your probability of failure has increased from P to P^4.
So really, I can see some applications where RAID 0 can be useful - I fit one of them. But for most desktop systems, it's not worth the cost. For systems with more than 2 drives anyway, it seems like a patentedly Bad Idea(TM). You really should've gone with RAID 5 - you'd still have striping, but you don't risk losing everything to a single faulty drive.
The fact that you reply anon says it all. Tweakers.net has a fine reputation among the Dutch, which is shown by the huge traffic amounts on their site (even when not being slashdotted) and their memberdatabase on both the forums and the site.
The quality of their forums and their articles are both very high, mostly concerning hardware.
The fact that this article was translated means they want to be a serious contestant in this discussion against major English sites.
Writing an article in Dutch which shows the contrairy of something said in English wouldnt be fair to those concerned, would it?
(:
Shouldn't that be 1-(1-p)^4?
p^4 would give you a decreased failure probability.
So that say there is a 1% chance of failure over 3 years for a given drive. Using the first formula, using 4 drives in raid 0 would increase the chance of at least one drive failing (and consequently all) to 3.94%.