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Question on RAID 0 settings...HD Video editing workstation

mark319
mark319 asked
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Last Modified: 2007-12-19
OK windows xp workstation for video editing.  150gig raptor boot drive, yada yada yada.  so 3 WD 500gig drives to be setup in raid 0 on an areca 1220 pci-e raid card with a stripe size of 128k (cause that's what I want, performance no exceptions, could care less if one fails one day and everything is lost).  you have to set your unit allocation size inside windows when you format the new raid partition. Also do you guys set it to 128k or leave it at default (which is 4k I think)?????

Thats what I'm worried about is setting the unit allocation size to be the best for me.  if I leave it at 4k and am working in a file thats 12gigs.  not sure if thats the best setting.  but if I set it to 2megs am I losing performance on that 12gig file?

PLEASE DONT come explain RAID to me, I know what it is. AND PLEASE DONT explain stripes and clusters and how they're different things. I just want to know what you guys are setting these 2 settings to and why.

thanks so much in advance, I'm pretty sure this areca card is one of the better that I can buy for my needs and I want to make sure that I'm setting it for the best performance.
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Top Expert 2012

Commented:
I have that card with 5 250GB Samsung Spinpoint drives in a RAID-5 configuration.  It doesn't do too badly, as measured  with HDTune starting at sustained transfer rates of 250MB/sec and ending at 170MB/sec.  I chose a stripe size of 64KB, and I use it for large video capture files (5GB).  The size you choose is a balance between head positioning and transfer performance, as outlined here: http://www.storagereview.com/guide2000/ref/hdd/perf/raid/concepts/perfStripe.html
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Commented:

If you files are large,then a larger cluster size is OK and will aid in performance.
You will lose functionality for things like defrag and compression if you use them

If they are small,you still get performance,but you end up with lot's of slack space which is a very inefficent way of using the disks.

The reason why they are at 4K is that it is an efficent way to store files.
If you have say a 26K file ,then you use only 7 4K clusters.

If your cluster size is 64 or 128K ,yeah,it only takes up one cluster,but that cluster is less than 50% full.

So your 500 gig drives can litterally contain a whole lot less data than advertised.

You can theoretically have 1.5 terrabytes of storage and only 500 gigs of data using all of that space.

Author

Commented:
well, as research has already told me for us video guys with large files 128k is the optimal stripe size.  so I already know this, what I'm looking for is info on what is the best NTFS "unit allocation size" to set for working with the large files.  default is 4k but will it matter if i change it to say 512k or 2 meg or 8meg, etc...  Would I notice a speed increase going with a larger UAS????
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Top Expert 2012

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Cluster size is a function of partition size: http://support.microsoft.com/default.aspx?scid=%2Fdirectory%2Fworldwide%2Fen-gb%2Fdefault.aspx%3Fscid%3Dkb%3Ben-gb%3B314878%26ln%3Den-gb

"NTFS file compression is not possible on drives with a larger allocation size." - this is why Windows chooses a maximum of 4K, which you can override.  If you don't use file compression, then going larger to handle large files is beneficial.
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Author

Commented:
jesus christ, someone tell me what UAS to set that will give me the best performance.  NOT NOT NOT the stripe size, my stripe is 128k and will stay 128k.  Someone that knows please give me a number/setting (as in "default", "512k", "1024K","2048k", etc...) that will be the BEST unit allocation size for handling large file sizes in my NTFS partition.  thanks again  
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128k stripe and 128k cluster size .

What is unclear about that?
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As pgm554 says, you align the cluster size with the stripe size for best efficiency. You can also use multiples of the stripe size for the cluster size - so 256K, 512K, 1024K or 2048K - although you're unlikely to see any performance improvement (or degradation) as a result.
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Commented:
Don't forget to align the Windows partition using diskpar.exe (part of the Windows 2000 Resource Kit - download from Microsoft). The latest W2K3 version of dispart.exe includes the functionality of diskpar.exe and *may* work in XP. Diskpar.exe for W2K definitely does work for XP.

http://geekswithblogs.net/ntpro/archive/2005/08/11/49948.aspx has more information.

Author

Commented:
lol, sorry pgm skipped right over your "Stripe size and cluster size should be the same if you want performance." line :).  I'm gonna try 128k/128k and see how it runs.  never heard of the diskpar thing gonna that today.
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