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 Need to change block size
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cgunner
Yak Posting Veteran

95 Posts

Posted - 07/26/2005 :  15:33:19  Show Profile  Reply with Quote
I have all of my data files on a RAID 5 drive with the default block size (512K). I have read that you will get better performance setting it to 64K when formatting. I was looking for an easy way to do this. Will simply shutting down SQL, copying the directory structure to another disk, formatting, copying the data back and starting SQL work?

eyechart
Flowing Fount of Yak Knowledge

USA
3575 Posts

Posted - 07/26/2005 :  15:43:04  Show Profile  Reply with Quote
you will most likely get a minimal performance gain from this. IMHO, the effort required to switch over is not worth it. However, changing your RAID 5 to RAID 10 would be more worthwhile if you are seeing performance issues due to slow disk.

In order to justify the work involved you would want to show that your slow disk IO is a bottleneck in your system. Usually adding a bit more RAM to the buffer cache recitifies this problem, unless you are running a large data warehouse.

Anyway, to answer your question, you are correct in the the steps neccesary to accomplish this. Make sure that the drive letter assignment is the same.



-ec
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cgunner
Yak Posting Veteran

95 Posts

Posted - 07/26/2005 :  15:53:50  Show Profile  Reply with Quote
It is a data warehouse. The server does 90% reads to 10% writes. Other than changing the RAID and Block configurations, are there any other considerations. I want to cover all the bases if I attempt this.
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cgunner
Yak Posting Veteran

95 Posts

Posted - 07/26/2005 :  16:07:30  Show Profile  Reply with Quote
Do you also set the Stripe Size to 64K if you migrate to RAID 1+0?
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eyechart
Flowing Fount of Yak Knowledge

USA
3575 Posts

Posted - 07/26/2005 :  16:50:43  Show Profile  Reply with Quote
if this is a data warehouse then going RAID 10 might be overkill for your data. RAID 5 performs well on reads, it is poor on writes. However, you would still use the 64K stripe regardless of RAID configuration.

How large is your database? how much RAM in your system?



-ec
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MichaelP
Jedi Yak

USA
2489 Posts

Posted - 07/26/2005 :  16:56:09  Show Profile  Visit MichaelP's Homepage  Reply with Quote
What's the Stripe size for your RAID array? That's part of this equation as well.

I remember someone telling me that the 512k NTFS block size is optimal is most cases, and it would be hard to measure the performance gains of changing the block size. I'm guessing you've onyl got a hadnful of disks in this array, so these small gains will mean nothing, if there is anything to gain.

On a larger disk subsystem (tens or hundreds of disks) a small gain is a really big deal.

Michael

<Yoda>Use the Search page you must. Find the answer you will. Cursors, path to the Dark Side they are. Avoid them, you must. Use Order By NewID() to get a random record you will.</Yoda>
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cgunner
Yak Posting Veteran

95 Posts

Posted - 07/27/2005 :  07:44:29  Show Profile  Reply with Quote
I have a 40 GIG DB with one of the tables containing 30 Million rows. The box has 8 GIG of RAM. I have six drives configured in a RAID 5 set now. They are formated with the default block and stripe size.
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