Optimum RAID Blocksize

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Level 1

4 points

Optimum RAID Blocksize

My Xserve RAID was formatted with the default blocksize of 32K.

I am running two Raid 5 arrays (one on each controller) each consisting of 4 500 MB drives, and combining the two arrays into one Raid 50 drive using Apple Disk Utility.

I am using the Raid50 drive as a Final Cut Pro video/audio capture drive working with 10bit uncompressed 720x486 NTSC. I plan on moving to uncompressed HD video at a future date.

How can I know if the 32K blocksize is optimum for me? Checking different sizes is not an option given that it takes two days to reformat the drives. I can't find any information about this on the Apple site.

Thanks,

Clyde
clyde@azebra.com

4 x 2.5 GHz PowerPC G5 Mac OS X (10.4.3)

Posted on Jan 2, 2006 10:45 AM

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Answer 1

Jan 2, 2006 11:27 AM in response to WildClyde

Hmmm... I don't even know where you can specify the block size when formatting in RAID admin. Are you talking about what you specified in Disk Utility?

You can change the prefetch settings on the RAID if you want (this only requires a reboot of the controller, not a reformat)... but the RAID is pretty quick with the default of 8... why not give it a try.

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Answer 2

WildClyde Author

Level 1

4 points

Jan 2, 2006 12:00 PM in response to William Lloyd

William,

The RAID blocksize is an option that defaults to 32K when you create the RAID array in the RAID Admin utility Create Array dialogue. This is NOT the same as the RAID Admin RAID controller cache setting. And it is not specified in the Disk Utility program.

I assume that this is the minimum amount of data that can be written or read from the RAID array. What I don't know is whether a 32K block is written to each drive.

Note: My aja System Test utility trials for 10bit 720x486 video show that the RAID controller cache setting of 8 stripes is the optimum one for me.

Clyde

4 x 2.5 GHz PowerPC G5 Mac OS X (10.4.3)

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