Storage Planning

Hi all,

We are setting up a new storage system for our company and I wan't to know if i'm running the best configuration possible;

The mission is to set-up a storage subsystem for our backup server, we have more then 400 backup jobs running at night from 200 servers.

Configured for Sequential Read
I'm using RAID 6 with NO spares
Using 512 KB for segment size
Using a combination of 2 MB / 4 MB stripe sizes for large data transfers
Enabled cache read-ahead

We are using a IBM DS3512 with DUAL controllers and it is attached to our server with two 6GB/s HBA controllers.


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BigSchmuhConnect With a Mentor Commented:
Your settings looks like more "sequential read" capable than "sequential write" capable...and I would assign backups to the "sequential write" category.

Looking at §4.3.6 Cache parameters (p.166 or 187) of redbook shown me some options.

In your case, I would:
-Use the largest "Segment size" of 512KB
-Use RAID 6 arrays of 8 drives for 3x8 arrays/LUN and a "full stripe" of 3MB
-Enable Write caching (with mirroring and requiring a working battery)
-Enable dynamic read prefetch
Are you only concerned about the restore times for this? How many disks are in each Raid set?
xissAuthor Commented:
Thanks for the responses, if have set the following on our storage system;

Sequential Write;
o      Used the largest "Segment size" of 512KB
o      Used RAID 6 arrays of 8 drives for 3x8 arrays/LUN and a "full stripe" of 3MB
o      Enabled Write caching (with mirroring and requiring a working battery)
o      Enabled dynamic read prefetch
o      Cache block size based on the I/O profile is set to 16 KB in order to improve performance.

I have one question remaining, what is the difference between Sequential I/O or Random I/O?
Sequential io are issued by any application that read or write succeeding sectors (ex : read a 1GB file)
Random io are issued by apps that r/w sectors almost randomly (database data files are usually accessed on that "randomly choosen" way
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