RAID-0 defrag

[Frosteh]

Hi [H]'ers, I have a 2x36Gb Western Digital Raptor 10,000 RPM (SATA) in a RAID-0 configuration (NV RAID on my Asus Mobo), which I boot off to get nice speeds within windows for loading etc.

My question is, Is a defrag a good or bad thing for a RAID-0 array?

It seems like a silly question but because of the nature of a stripped array (writing in alternating blocks of data to each drive) I was wondering if a defrag is going to order these blocks so that the files only end up on one drive.

I suppose it depends on how the OS (this is a winxp defrag) see's the hard drives, i would have thought the RAID controller would take care of this sort of thing at hardware level and make sure the OS see's the first block on the first drive, the 2nd block on the 2nd drive etc, so a defrag needs no special aranagement to keep the speed up on a RAID 0 array.

Thanks in advance for any help, cheers.

*edit*

The main reason im asking this is after a quick disk analysis winxp shows a fair bit of fragmentation, and the disk is less than 50% full, its never really gone over 50% so I wouldnt expect any large amounts of fragmentation in the first place.

 

[unhappy_mage]

Defragging will definitely help speeds. The OS will sort blocks into order on the disk as it sees it, which means they'll end up on alternating disks.

However, you're probably losing speed with a 2x36 setup as opposed to a 1x74 or 1x150 setup. Upgrading will give you more speed than defragging. And booting off it means that you have to wait for the RAID bios to execute (and then Windows has to redetect the drives), slowing your overall powerbutton-to-desktop time.

 

[matguy]

Defragging will definitely help speeds. The OS will sort blocks into order on the disk as it sees it, which means they'll end up on alternating disks.

However, you're probably losing speed with a 2x36 setup as opposed to a 1x74 or 1x150 setup. Upgrading will give you more speed than defragging. And booting off it means that you have to wait for the RAID bios to execute (and then Windows has to redetect the drives), slowing your overall powerbutton-to-desktop time.

Loosing speed? If he was looking to change his configuration, I could say he'd be loosing speed by going to that config, but he's already there, he's just asking about defrag. Really, save your crusades for other questions. Defraging is free, and yes it will help.

Defraging a Raid0 array helps in exactly the same way as it helps on a single drive, by keeping head seeks down. The Raid0 hardware only makes the disks in to odds and evens (or 1/3rds, 1/4's, whatever) that the os sees as a standard drive that is addresses the same way. If a file was going to be fragmented by the file system (drives don't fragment a file, the file system does) in a single drive, it will get the same treatment in a Raid0 striped array. Plus the heads will seek in unison (generally) in a Raid0 striped array just as they will in a single drive, so if the file system has seperated file that are often accessed together, but are seperated accross the drive will still seek accross the drive as they will in a single drive. Defrag can often help put those files together as well as pack files to the front of the drive(s) to reduce head seeks.

 

[Crosshairs]

Loosing speed? If he was looking to change his configuration, I could say he'd be loosing speed by going to that config,

I thought that the single 74 was faster that the Raided 36's..

 

[unhappy_mage]

Loosing speed? If he was looking to change his configuration, I could say he'd be loosing speed by going to that config, but he's already there, he's just asking about defrag. Really, save your crusades for other questions. Defraging is free, and yes it will help.

I did mention that defragging will help. But he said here:

I am very pleased with my 2x36GB Raptors in RAID-0, so pleased in fact that i'll add another 2 later this year and have a 4 drive RAID-0 primary, maybe ready for vista, who knows.

4 drives in raid 0 is both a huge possible point of failure and a waste of money IMO. Get one raptor-X or 2 74s not in raid, and it'll be just as fast if not faster, less driver hassles, and less complexity.

http://faq.storagereview.com/SingleDriveVsRaid0

 

[Frosteh]

Ok thanks for the help.

4x RAID should give the same sort of multiplier of speed ontop of what I already have, as i said I dont have anything important stored on the drive, ever, money isnt a massive object if im aimng to upgrade around the time vista comes out, the drives arent too expensive now and they'll be cheaper then.

Does anyone have any benchmarks showing off the performance difference between the 36 and 72 gb drives, i find it hard to believe a RAID 0 array with 2x36gb raptors is slower than 1x 72gb

 

[Frosteh]

Just googled a few benchmarks and a few have said its not worth it yadda yadda yadda, which I think once again proves without a doubt that synthetic benchmarks just aren't reliable today.

When loading game files before playing a level such as in BF2, I get a much faster load time than the average player, much faster. We're talking easy 15 seconds, on average i'd say its as much as 25-30 seconds over players with slow drives and unoptimised PC's

Your loading data straight from the drive into RAM, large chunks of it, speed at which the drives can supply that data is really the bottleneck.

 

[matguy]

Yeah, I doubt upping the count to 4 drives would double the performance delta you experienced by going to 2. Each doubling of drives will usually show a performance increase, but not as much as you experienced the first time, untill you hit the limits of either the card or the system bus, then you can add drives all day long and it won't make a difference untill you change your Raid scheme/level. I probbaly will do some playing around next week with some promise v-trak raid chassis I have sitting at work that are filled with 15x identical 250GB Maxtor 7200rpm drives. Being they can handle Raid 0, 1, 3, 5, 10, and 50 accross 15 drives, I don't see a better way to do a apples to apples test. I'll also see just how much of a performance hit I see between windows striping and native hardware striping.

 

[unhappy_mage]

Here's a test with 2xraptors versus 4xraptors, all 36gb. Here's a person who tested 36gb raptors in raid 0 versus a single 36 versus a single 74. The 74 runs away with it. And here's a page with game loading times for a 36, a 74, and 2 74s.

To quote Ananadtech:
Bottom line: RAID-0 arrays will win you just about any benchmark, but they'll deliver virtually nothing more than that for real world desktop performance. That's just the cold hard truth.

 

[Crosshairs]

Nice post...I mentioned earlier that I was pretty sure the Single 74 was quicker than the raided 36's.....looks like I was right....I knew I saw some tests somewhere that showed that....

I had 2 raided 36;s I sold them and bought 2 74's.....I dont run the 74's in raid though......And my system is faster than it was with the 36's......
But whatever, I really could care less what someone else does, thats why I usualy stay out of these posts..

 

[rodsfree]

Here's a test with 2xraptors versus 4xraptors, all 36gb. Here's a person who tested 36gb raptors in raid 0 versus a single 36 versus a single 74. The 74 runs away with it. And here's a page with game loading times for a 36, a 74, and 2 74s.

To quote Ananadtech:
Bottom line: RAID-0 arrays will win you just about any benchmark, but they'll deliver virtually nothing more than that for real world desktop performance. That's just the cold hard truth.

All that might be true.....
But I have a pair of the 36GB Raptors in RAID0 and I'm generally the first into a map on my clan's CS:S server. And most of these guys have the 16MB cache drives or single 74GB Raptors.. And that's including the guys that have a super low ping of 8-12 and me pinging at 50-70.

But I'm getting a 150GB Raptor and I'll be able to see for myself.