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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"
A common misconception is that striping beyond 2 drives is "worthless." That simply isn't true: remember that the inside of the drives, close to the spindles, has a transfer rate that is nearly half what it is on the outside cylindars. By striping 4 drives togeather, about half the bandiwdth is wasted near the FRONT of the drive, but near the tail, it's almost all being used. The effect is that the drive feels uniformly quick no matter what part of the drive you are reading from!
I personally jumped from a single drive to a 4-drive SATA raid-0 system, composed of 120GB drives from two different manufacturers.
The system screams.
I can't tell you how nice it is to have my computer boot in half the time... how your system feels like you always wished it would feel. You can add all the memory you want, all the processing power you want, but if you can't feed the computer, it's all pointless.
The only thing I wish now was that my system had a faster and/or wider bus that would allow me to take advantage of all the currently unused bandwidth available from the four drives.
A common theme, revisited several times, in the article is that the other conclusions were wrong because they used low-load testing.
"A safe conclusion would be that a Business Winstone 2004-benchmark alone is not a good starting point when testing RAID 0 performance. On the contrary: to have some reliable tests, we will need to put heavy loads on the array."
In essence, if my understanding is correct, they're saying that the value of a RAID 0 setup is under constant extreme loads, not the loads created by business applications or games. Isn't this entirely the point of the articles in question - That given the sporatic, generally light load of even power users, RAID 0 is not really that beneficial (as random access plays even more of a part than gross throughput)?
Even under perceived heavy I/O loads, the reality is often that the hard disk is under-used - I occasionally compress videos from miniDV to DVD, and my CPU would need a four or five fold increase in speed to even begin to put pressure on the single 7200 RPM hard disk.
But for the majority of us normal people who are running huge multi-threaded database applications on their desktop machines
Sorry, most slashdotters are NOT using Longhorn yet.
Just the thought of using RAID-0 makes me shiver. The only people who should use this are people who keep good backups, and like using them. The speed gains are of little use for individuals, and for the professionals or corporations that might actually want the speed-up, the chances of data-loss are too high.
That's not to say there isn't a purpose for RAID-0 - it teaches people how useful backups are. The hard way.
Just because you're paranoid doesn't mean there isn't an invisible demon about to eat your face
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.
Yeah, I did an absolute double take when I got to that part. They spend an entire article bashing the two of the most methodical sites out there on methodilogy and then try to use a completely unscientific poll as backing evidence to their claim? Let alone a poll that's naturally pre-biased to a particular conclusion. It really puts the validity of the rest of the article into question. If that's acceptable evidence, what other shoddy methods are acceptable to them?
If you've spent the extra money on RAID 0, you're going to believe there's a difference going in. Hell, I've done it myself - I have 2 machines with RAID 0 setups, but that's because they're commonly used for working with multi-gig sized files in photoshop - IE: I actually need the strong sequential speed.
For normal desktop setups, I'd absolutely agree with AT and SR on this one. Unless you're doing massive amounts of large sequential reads/writes, you're just not going to see a difference in speed worth the cost of another drive and the major increase in potential failure and data loss. Remember, by adding that second drive, your chance of failure goes up *exponentially* which is something a lot of hardcore "tweakers" forget.
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
'RAID 0 (Score:0, Redundant)' LOL!
Nope, reliability goes down.
Let's suppose that both the 80Gb and the 160Gb drives have a possibility of failing in a month of 10%.
Now, with the 1x160Gb you have 10% of having a failure this month, obviously. What's the probability for both drives?
Well, since each one won't fail 90% of the time, the probabilities of both not failing is 81% (0.9*0.9). The rest, 19% is the possibility that one or both fail, therefore, instead of a 10% failure rate, you get 19%... nearly twice!
A friend who works with NAS/SAN systems jokingly told me that a hard drive exists in only 2 states:
1) Failed
2) About to fail
Tb.
An OPEN mind is a beautiful thing...