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Disk Utility - Striped RAID - Block Size ?

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phosphene
Disk Utility - Striped RAID - Block Size ?
on Aug 7, 2006 at 10:29:10 pm

I just purchased an external 2 bay sata2 setup for my macbook pro 2.16ghz.

For use with final cut studio, I am creating a small 2 disk striped raid with apple disk utility.

In the raid options, how do I decide which block size to use? Do i base my decision on the drive type, or on the environment the raid will be used in, or other?

I have 2x Seagate Barracuda 7200.10 ST3320620AS (Perpendicular Recording Technology) 320GB 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive - OEM

MacBook Pro 17" 2.16ghz
2gb ram
7200 rpm int hd
FCP 5.1.1
OS 10.4.7


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phosphene
Re: Disk Utility - Striped RAID - Block Size ?
on Aug 8, 2006 at 2:22:04 am

hmmmm. enclosure manual says 64 or 128k for best performance


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Tony!
Re: Disk Utility - Striped RAID - Block Size ?
on Aug 9, 2006 at 9:57:40 am

I use 128k for video RAID's. However, I've used 32k and it still works great. Currently I'm using Xserve RAID's, but the suggested 64k and 128k are correct for any RAID used for video.

Tony!


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phosphene
Re: Disk Utility - Striped RAID - Block Size ?
on Aug 10, 2006 at 6:41:57 pm

OK thanks.

Just so I'm 100% sure exactly why one would choose 64 or 128. So it's an environment based decision and not hardware based? ie: I would pick 128k over 64k because of how big the files I am working with(video)...nothing to do with the model of the hard drive requuiring a certain block size.?

A larger block size means less reading to the drive so performance is improved even more? Then why not crank it all the way up to 512k or more?


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Tony!
Re: Disk Utility - Striped RAID - Block Size ?
on Aug 12, 2006 at 7:14:34 pm

[phosphene] "OK thanks.

Just so I'm 100% sure exactly why one would choose 64 or 128. So it's an environment based decision and not hardware based? ie: I would pick 128k over 64k because of how big the files I am working with(video)...nothing to do with the model of the hard drive requuiring a certain block size.?

A larger block size means less reading to the drive so performance is improved even more? Then why not crank it all the way up to 512k or more?

"


What you are saying is generally correct as far as my understanding. However, I base my recommendations on tests I've done and what I've read others have done. The optimal block size does seem to vary and if you want the best performance you need to test it with your own system. Meaning format it with 32k and run the AJA, BlackMagic or other speed tests (depending on your hardware) write down the numbers, then try a different block size. Keep doing that until you tried them all and find out for yourself. For me it was the 128k block size by a narrow margin. The 32k and 64k were acceptable on my system as well.

It's been awhile and I don't really remember where I read the outcome of other peoples tests, but you might try searching the obvious Cow forms to see if you can get anymore insight. The Apple discussions Xserve RAID forum might have some info as well, but they erase old posts, so it would have to be something fairly recent.

Also, you might want to speak with AJA, BlackMagic, etc to see what they recommend. I use Xserve RAID's and there maybe a hardware difference (I run RAID 50, over Fibre, and the size of my storage considerably bigger as well.

So no specific answers, either test and pick what gives you the best numbers, accept a general recommendations, or ask the capture card manufacturer what they believe is best.

I hope that helps,

Tony!


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phosphene
Re: Disk Utility - Striped RAID - Block Size ?
on Aug 16, 2006 at 8:05:11 pm

sweet, thanx


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