Western Digital's Raptors in RAID-0: Are two drives better than one?
by Anand Lal Shimpi on July 1, 2004 12:00 PM EST- Posted in
- Storage
Putting the Redundancy in RAID: RAID-1
The next type of RAID that we'll talk about is RAID-1, otherwise known as mirroring. We won't be benchmarking RAID-1 here because, for the most part, there's no performance increase or decrease. As the title of this page implies, RAID-1 is done for redundancy.
Writing to a two-drive RAID-1 array
Unlike RAID-0, there is no preprocessing done on the data before it is sent to the hard drives. Instead, with RAID-1, a duplicate of everything written to drive 0 is written to its mirror drive. The benefit of RAID-1 is that if one drive fails, you have a perfectly working backup that can take over until you have replaced the failed drive. You have effectively doubled a single hard drive's mean time between failure by using two in a RAID-1 array. You'll notice that this is the exact opposite of RAID-0, but the downside to RAID-1 is that you spend twice as much on hard drives without getting any additional capacity or performance, just reliability.
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Denial - Friday, July 2, 2004 - link
A$$ Masher,You seem to be the only person turned on by my system. Sorry, but I don't swing that way. You'll have a better chance at the internet cafes over in Chelsea.
TheCimmerian - Friday, July 2, 2004 - link
...Anyone have any thoughts on RAID0 for DV capture/editing/rendering?...masher - Friday, July 2, 2004 - link
#71, the statistics and applicability for MTBF and MTTF are a bit complex...so much so that most drive manufacturers themselves usually don't apply them properly (or intentionally mislead people).Technically, you're correct...RAID0 doesn't halve MTBF. However, for what the average user means by "chance of failure", a two-disk Raid0 array does indeed double your chance of a failure.
As to your comment of Raid-0 loading maps faster...true if its a large file (10MB+) and probably not discernably noticeable till you're in the 20-40MB range. For tiny files or heavily fragmented ones, it may even be slower.
Z80 - Friday, July 2, 2004 - link
This article was very informative. However, the statements that RAID0 cuts MTBF in half and that RAID1 doubles MTBF are statistically incorrect. Also, RAID0 does improve game performance especially when large game maps are involved (i.e., BF1942, BF Vietnam, Far Cry). It definitely provides an advantage in online FPS games by loading large maps faster and giving RAIDO equipped players an advantage in first choice for weapons and position. Your tests probably didn't measure map loading times.GokieKS - Friday, July 2, 2004 - link
"What's the difference between losing one 74gig Raptor in RAID-0 array or one 160gig stand-alone drive? THERE IS NO DIFFERENCE!"There is. The chance of you getting a HDD failure increases with every drive you add. A 2 disk RAID-0 array will have the same chance at failure as 2 independent non-RAIDed drives. The difference is, with the independent drives, you lose one drive's worth of data when it fails. With the RAID-0 array, you lose two.
~KS
sparky123321 - Friday, July 2, 2004 - link
I keep hearing about double the cost and the additional risk associated with a RAID-0 array.First off, double the price gets you DOUBLE the capacity of a single drive. It's a wash price wise. On top of that, you increase disk performance by up to 20+%. Normally, there tends to be a decrease in performance as capacity increases when comparing similar generation drives.
Secondly, with regard to risk. What's the difference between losing one 74gig Raptor in RAID-0 array or one 160gig stand-alone drive? THERE IS NO DIFFERENCE! If you don't have a recent backup, you've lost everything. Just spend an additional $90 to buy a backup 160gig 7200rpm IDE and use Acronis to do a complete disk mirror every week or two. If you lose a RAID-0 drive, you can just boot off of the backup drive and be up and running in a matter of minutes. Worst case, you've lost you're most recent work only.
Power to the Raptors and I think I'll stick with my RAID-0 array!!!!!!!
abocz - Friday, July 2, 2004 - link
I think #63 summed it up pretty well. For most real world usage the RAID0 setup never gets to shine because of the ratio of seek times/data transfers. Lower (7200) RPM drives will only compound the situation since their seek times are worse. Finally, add to this phenomenon the fact that the ratio of seeks will increase over time as fragmentation increases.Which begs the question of how well defraggers work in a RAID 0 setup? Anybody know?
Inferno - Friday, July 2, 2004 - link
Maybe you should try this test with some lesser drive. The raptors are kind of the be all end all drives. Maybe a pair of midrange Maxtors.binger - Friday, July 2, 2004 - link
#61, jvrobert is right in saying that the advantages of a raptor-raid0 are restricted to faster boot-up times and smoother handling of very large files, eg when it comes to dv.although i have heard similar statements before, whether a raid0-array of two 160gb samsung drives comes close to the performance of a single 74gb raptor drive, i don't know - i would surely appreciate being pointed to an appropriate review or at least a couple of significant benchmark results.
jvrobert - Friday, July 2, 2004 - link
Two points:First, it doesn't matter much what card you use for RAID 0. There's no parity calculation, so onboard hardware won't help much. Probably Windows striping, Intel RAID, VIA RAID, Highpoint RAID, etc.. are within 1 percent of eachother.
Second, this is a limited test that comes to an overgeneralized conclusion. As some have mentioned - these are raptors. I have a single raptor as my OS disk. Where RAID helps is with slower drives - you can get a "virtual" raptor of e.g. 360GB by buying 2 cheap, quiet, cool Samsung spinpoints.
Third (OK, 3 points) - it only tests games (which don't use much hard disk IO) and business (again, disk speed doesn't matter much). I'm getting into video now, and RAID 0 will certainly improve performance there. It will also help with load times of the OS and of large applications.
So the article comes to an over-general conclusion limited on a few quick tests.