raid 0 technical question... at DVinfo.net

Mark Leonard · January 7th, 2007, 11:04 AM

hey guys, I have setup 2 500gig WD RE2's in a raid 0 with a 128k stripe size. 128k was the largest that the sil bios would allow. now once getting into windows and going to the disk manager, I've set it up as a primary partition formatted in NTFS and selected the "default cluster size". now windows default cluster size is 4k if i recall. so now does windows see this partition as 128k clusters or 4k clusters.

little background here. this machine is a intel xbx with a core 2 duo 6800 with a 150gig raptor as the boot drive. i do my video editing and hd captures on this machine. so the 1gig raid 0 is for obviously hd data capturing/storage for editing. file sizes range from 300meg to 15gig so a large cluster size will benefit me more.

now on the board is a sil 3120 raid controller (i believe) however I also have a promise fasttrak S150 TX4 raid as well but I'm guessing the SIL is more powerful and faster being that it's so much newer? (please if anyone thinks the promise is better than the onboard SIL let me know)

so with 128k cluster sizes being the largest that you can set(on both the SIL and the Promise), setting up the raid 0 in their respecting bios leaves it at 128k? or when you add the disk in the disk manager can you change it to a larger or smaller size?

Harm Millaard · January 8th, 2007, 07:42 AM

Mark,

You are confusing things here. You are talking about a 128K STRIPE size versus a 4 KB CLUSTER size. The stripe size is a measure of how much information is striped over the stripe width, the cluster size is purely dependent on the file system in use, in your case NTFS, which works with fixed clusters.

In your case, using a Aid0, I left out the R because there is no redundancy in a Raid0, data are being written in 32 clusters at a time to each disk in your array. (32x4=128). If you do a Google for stripe size you will find a lot of valuable background info. Here is some info I found:

Stripe Width and Stripe Size

RAID arrays that use striping improve performance by splitting up files into small pieces and distributing them to multiple hard disks. Most striping implementations allow the creator of the array control over two critical parameters that define the way that the data is broken into chunks and sent to the various disks. Each of these factors has an important impact on the performance of a striped array.

The first key parameter is the stripe width of the array. Stripe width refers to the number of parallel stripes that can be written to or read from simultaneously. This is of course equal to the number of disks in the array. So a four-disk striped array would have a stripe width of four. Read and write performance of a striped array increases as stripe width increases, all else being equal. The reason is that adding more drives to the array increases the parallelism of the array, allowing access to more drives simultaneously. You will generally have superior transfer performance from an array of eight 18 GB drives than from an array of four 36 GB of the same drive family, all else being equal. Of course, the cost of eight 18 GB drives is higher than that of four 36 GB drives, and there are other concerns such as power supply to be dealt with.

The second important parameter is the stripe size of the array, sometimes also referred to by terms such as block size, chunk size, stripe length or granularity. This term refers to the size of the stripes written to each disk. RAID arrays that stripe in blocks typically allow the selection of block sizes in kiB ranging from 2 kiB to 512 kiB (or even higher) in powers of two (meaning 2 kiB, 4 kiB, 8 kiB and so on.) Byte-level striping (as in RAID 3) uses a stripe size of one byte or perhaps a small number like 512, usually not selectable by the user.

January 7th, 2007, 11:04 AM	#1
Mark Leonard Regular Crew Join Date: Aug 2006 Location: Mobile, Alabama Posts: 166	raid 0 technical question... hey guys, I have setup 2 500gig WD RE2's in a raid 0 with a 128k stripe size. 128k was the largest that the sil bios would allow. now once getting into windows and going to the disk manager, I've set it up as a primary partition formatted in NTFS and selected the "default cluster size". now windows default cluster size is 4k if i recall. so now does windows see this partition as 128k clusters or 4k clusters. little background here. this machine is a intel xbx with a core 2 duo 6800 with a 150gig raptor as the boot drive. i do my video editing and hd captures on this machine. so the 1gig raid 0 is for obviously hd data capturing/storage for editing. file sizes range from 300meg to 15gig so a large cluster size will benefit me more. now on the board is a sil 3120 raid controller (i believe) however I also have a promise fasttrak S150 TX4 raid as well but I'm guessing the SIL is more powerful and faster being that it's so much newer? (please if anyone thinks the promise is better than the onboard SIL let me know) so with 128k cluster sizes being the largest that you can set(on both the SIL and the Promise), setting up the raid 0 in their respecting bios leaves it at 128k? or when you add the disk in the disk manager can you change it to a larger or smaller size?

January 8th, 2007, 07:42 AM	#2
Harm Millaard Trustee Join Date: Aug 2006 Location: Rotterdam, Netherlands Posts: 1,832	Mark, You are confusing things here. You are talking about a 128K STRIPE size versus a 4 KB CLUSTER size. The stripe size is a measure of how much information is striped over the stripe width, the cluster size is purely dependent on the file system in use, in your case NTFS, which works with fixed clusters. In your case, using a Aid0, I left out the R because there is no redundancy in a Raid0, data are being written in 32 clusters at a time to each disk in your array. (32x4=128). If you do a Google for stripe size you will find a lot of valuable background info. Here is some info I found: Stripe Width and Stripe Size RAID arrays that use striping improve performance by splitting up files into small pieces and distributing them to multiple hard disks. Most striping implementations allow the creator of the array control over two critical parameters that define the way that the data is broken into chunks and sent to the various disks. Each of these factors has an important impact on the performance of a striped array. The first key parameter is the stripe width of the array. Stripe width refers to the number of parallel stripes that can be written to or read from simultaneously. This is of course equal to the number of disks in the array. So a four-disk striped array would have a stripe width of four. Read and write performance of a striped array increases as stripe width increases, all else being equal. The reason is that adding more drives to the array increases the parallelism of the array, allowing access to more drives simultaneously. You will generally have superior transfer performance from an array of eight 18 GB drives than from an array of four 36 GB of the same drive family, all else being equal. Of course, the cost of eight 18 GB drives is higher than that of four 36 GB drives, and there are other concerns such as power supply to be dealt with. The second important parameter is the stripe size of the array, sometimes also referred to by terms such as block size, chunk size, stripe length or granularity. This term refers to the size of the stripes written to each disk. RAID arrays that stripe in blocks typically allow the selection of block sizes in kiB ranging from 2 kiB to 512 kiB (or even higher) in powers of two (meaning 2 kiB, 4 kiB, 8 kiB and so on.) Byte-level striping (as in RAID 3) uses a stripe size of one byte or perhaps a small number like 512, usually not selectable by the user.