MD3000 Performance

[Sid Young]

G'Day,

How you configure your disks really depends on your data needs. If you
need to supply a system that is a high I/O transaction system, like a
very large exchange server, SQL or other DB system then mirrored and
stripped pairs may be the answer (RAID 1+0).  If you have a lot of
sequential writes in that high I/O environment then perhaps multiple
RAID5 luns striped at the OS might be a good solution. 

I come from a EMC CX600 and CX300 background and I use to setup raid
groups with 4 drives, each pair mirrored and then stripped and divyed up
into even LUNs of 40,20,10,5 and 1GB chunks, then if someone needed
200Gb for a fast system I could give then even allotments from a range
of raid groups to span their data over lots of spindles. 

If you need basic file storage or low I/O then just RAID5 might suffice
on slower disks.

You could also try a large group of mirrored pairs, strip them at the OS
to create lots of disk queues to handle the I/O requests and then use a
single hot spare per cabinet.

Some food for though... whatever you do, always remember that in most
OS's a single LUN is a single queue, so I/O will choke if you only have
one queue to write lots of data to.


Sid




-----Original Message-----
From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of Mahmoud Hanafi
Sent: Friday, August 08, 2008 9:04 AM
To: linux-poweredge at dell.com
Subject: MD3000 Performance

We just installed a MD3000 & MD1000. We ran some simple performance test

using XDD and iozone. We tested various raid group at the device and
file 
system level. We are seen some very poor performance.

Single Disk Raid0 sequential Writes= 20MB/sec

4+1 and 7+1 Disks Raid5 Sequential writes = 100MB/sec 

Is this performance typical? Any tuning suggestions?

Regards,
Mahmoud Hanafi

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