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RAID 0 performance makes no difference


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I have windows 7 installed on a raptor. I just put in 2 250gb to test raid 0 performance. In crystal disk mark i go around 160/ 140 for the raid0, 80ish for the single 250 not in raid and around 77 for the raptor. This is the top of the scores.

But when i transfered an iso file of about 4 gigs to the raid 0 the transfer rate was 80ish, i transfered it to the the single non raid the transfer was 77ish. I then tried transferring a bunch of files and the transfer rate was around the same. I did this several times. So crystal disk mark shows the raid 0 is obviously a lot better, but real world experience is not benefiting.

Is there something i need to look at.

I am using a quad core custom pc, using the built in raid from the mobo with 4gb of ram and win7 64 bit....

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  • 2 weeks later...

But when i transfered an iso file of about 4 gigs to the raid 0 the transfer rate was 80ish, i transfered it to the the single non raid the transfer was 77ish. I then tried transferring a bunch of files and the transfer rate was around the same. I did this several times. So crystal disk mark shows the raid 0 is obviously a lot better, but real world experience is not benefiting.

From Wiki:

The blocks are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, increasing bandwidth. RAID 0 does not implement error checking, so any error is uncorrectable. More disks in the array means higher bandwidth, but greater risk of data loss.

So, to put that short, RAID 0 will improve READ performance but NOT much for write performance, so what you experience is normal ;).

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Sorry puntomx but you're wrong raid 0 does improve read and write performance. In theory, a raid 0 with 8 drive should allow the speed to be multiplied by 8 in real world with software raid it doesn't increase as much as 4 times (but with hardware raid controller with write cache it can almost do it).

I think the problem there is either the format method (more precisely big cluster size for big files and aligned partition) as you can gain a lot in real world, or the source drive or destination drive.

The only way to test real world write speed to a (or an array) of drive is to use a Ramdrive or a faster (raid array) source drive.

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Sorry puntomx but you're wrong raid 0 does improve read and write performance.

I said "not much", but it does indeed, be sure to use 64kB blocks and up (128 better). Read performance is even good with smaller blocks, write performance is SO variable, believe me it is ;).

I'm sure the OP has small blocks so what he got is normal, that's what I wanted to say although I wasn't 100% clear (forgive me, it was a lazy Sunday ) :ph34r:

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  • 8 months later...

On one 4GB file the Raid-0 should write faster than a single disk.

But then, quite a couple of things can go wrong, or say, have to be adjusted, before a Raid-0 runs properly. Unfortunately, most benchmark software is inadequate to test a Raid-0; IOMeter is excellent but difficult to use; Atto gives a first sight that is far from perfect but makes more sense than other programmes.

Examples of tuning:

- Stripe size, as already said. With present disks, it would better be 512kiB or 256kiB, so take 128kiB if this is your Bios' limit

- Volume alignment

Then, you shouldn't expect a file to write at the speed told by the benchmark, because the OS has to write the Fat or Mft at the same time, thus moving the disk's head, and so on.

Besides, I hope the source for your file is not the same disk where you write!

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