November 5, 2002 at 2:16 am
If I've got 5 disks available. What is the best configuration for a pure database server ?
I'm thinking on the lines of:
2x18GB System & Application disks RAID 1
1x18GB Log
2x36GB Data disks RAID 0+1
Or is a RAID 5 over all disks better ?
Thanks for any tips.
Neville Higgs
WAZ Mediengruppe
November 5, 2002 at 7:51 am
I think you want some fault tolerance on your LOG disk. I might consider making the log and data disk (3 disks) a raid 5.
Gregory Larsen, DBA
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Gregory A. Larsen, MVP
November 5, 2002 at 8:22 am
I agree that putting the logs on the RAID5 gives you some fault tolerance, more importantly gives you three disks instead of two for your data. Although not recommended practice, the small number of disks can definitely be limiting. I'd suggest at least putting the logs on the same disk as the OS, or for better performance just stripe all five as RAID5. OS actually uses very little disk. It's convenient to have it isolated, but with five disks I'd rather put them to work.
Not everyone will agree!
Andy
November 5, 2002 at 8:33 am
If I'm not mistaken, you need to keep in mind that with RAID 5, the size of each disk in the array will be considered usable up to the size of the smallest in the array, so your 2 36GB disks will only be usable as 18GB, if you place them in the same array. Ideally in RAID 5, all disks should be the same size.
-Dan
-Dan
November 5, 2002 at 10:34 am
Having only 3 disks in an array is not going to give you much in terms of performance, you would probably be better off with 1 array of 5 disks.
Of buy some more disk, 5,000 pounds for a box of 14 disks, and you dont have to fill it.
Simon Sabin
Co-author of SQL Server 2000 XML Distilled
http://www.amazon.co.uk/exec/obidos/ASIN/1904347088
Simon Sabin
SQL Server MVP
http://sqlblogcasts.com/blogs/simons
November 5, 2002 at 12:37 pm
2x18GB System & Application disks RAID 1 -- This would be fine
1x18GB Log -- No redundancy, so you lose it it is gone.
2x36GB Data disks RAID 0+1 -- You can't do this with 2 drives (4 drive minimum to make a raid 10, 0+1)
You configuration is probably best as
2x36GB Sys and App in RAID 1 (mirrored for redundancy).
3x18GB Data and Log in RAID 5 (stripe with parity).
Now if you can add another 18GB drive to the mix then 4x18GB in to a RAID 10 (Stripe 2 mirror to other two set, has best overall preformance).
But ultimately your goal should be to move the logs to another drive, always thou consider redundancy or you will run the risk of data loss.
Also, you cannot mix disks in a RAID 5 array and still use the other pieces so 1x18+2x36GB would yield the same as 3x18GB and no more.
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