Which stripe size to use for RAID 0 array? And RAID 0 question EDIT: Another RAID 0 question

[J3anyus]

Hey everyone. I'm setting up a RAID 0 array running 2x60GB Western Digital 5400 RPM drives. I'll be doing a lot of gaming on this box, and a fair amount of DivX encoding, along with some less intensive things (word processing, minesweeper, random things). The array will be running off a Highpoint HPT370A RAID controller that is on my EPoX EP-8K7A+. I'm thinking that either 16KB or 32KB should be the stripe size to use, but I've never done RAID 0 so I'm not totally sure. Can anyone give me any advice, or point me to anywhere that could help? I couldn't find anything on AT, and couldn't find too much help through Google either. Thanks.

J3

Edit: Forgot to mention this...I'm planning on partitioning this into 3x40GB partitions? Are there any problems with doing that while running RAID 0?

Edit #2: Probably a dumb question...can I change stripe size after creating my array? Meaning, can I make the array, install Win2K, and then change the stripe size, and keep all my data intact, just to test if the different size speeds things up?

 

[John]

I have been using 32KB for a long time. Storagereview.com has some useful info on IDE raid.

 

[Cuular]

The age old question what is the best stripe size for a raid setup?

It all depends on what size files you are creating/accessing. The speed increase from raiding only kicks in if your files are big enough to be split across the different disks. If most of your files are under 32k, then using a 32k stripe will not buy you anything. because the files most likely will not be "striped".

So the anser is pick the largest stripe size that will cause most of your files to split across the stripes. For most gaming applications with todays 3D shooters and stuff you can use MB stripes. For word processing I am guessing 32k is good. With Divx encoding again MB stripes would be good. Not to many files smaller than 5-10MB.

If you have the option, for what you say you are doing, I would go for 512k to 1MB. I am guessing your hard drives have at least a 2MB buffer on them. If not then limit the stripe size to 1/2 of the HD's buffer. This helps because then you can have 2 pending writes/reads to the hardrive before you have to wait for it to clear buffer and write/read to disk.

In a nutshell stripe size should be based on the size of the average file you work on and the amount of cache there is on the hard drive, and the speed of the drives. Setting the stripe size larger than the cache on the drive and you will be causing yourself to slow down. In a perfect setup with fast drives limit stripe size to 1/2 the buffer. With slower drives make it 1/4 or 1/8 of the buffer. You would like it such that for the most part your cache on the 2 drives could hold the data, without having to actually write it to disk until the CPU intensive part of the job is done. Basically store it in the disks cache until you have some extra CPU to flush it out.

With IDE drive caches being somewhat on the low side for large mpeg encoding you won't be able to fit the whole mpeg file in the drives cache's, so you hope they are fast enough to write out the current cached data while the mpeg algorithm is cranking on the next set of data.

Way to much info I am sure. Sorry about that.

 

[XMan]

How can you partition a 120GB RAID array in FAT32?

Can you have it all as one drive?

 

[Antisocial Virge]

<< How can you partition a 120GB RAID array in FAT32? Can you have it all as one drive? >>



Think so but you might have to use a fix from Microsoft for windows to see it all. I had 2 X 40 gigs and it would only show like 12 gigs or something like that. The problem was that the old version of FDISK can't handle anything over 62 gig or something like that.
Here is a very good faq on the problem on Abit boards.
http://www.viahardware.com/faq/kg7kr7/raid_controller.htm

 

[MichaelD]

Cuular,

That was one of the best "RAID Stripe Tutorials" I've ever read. I honestly read about a dozen different articles and experimented for about a week with stripe sizes before I found out everything you just said. They should include your entire post in the FAQ! Seriously. Great job.

 

[J3anyus]

<< How can you partition a 120GB RAID array in FAT32? >>

I'm gonna be running NTFS, 3x40GB partitions.


Cuular:
Thanks, your post was really informative. I never knew stripe sizes went that high, I thought they were only 1k, 2k, 4k, 8k, 16k, 32k, and 64k. I'll have to do some tinkering around to figure out what seems to work well for me.

Bump back to the top for (hopefully) the last question, added to the original post...

 

[obsol33t]

I can never figure out the format command in DOS for a 512k stripe size. Does anyone know?