PE2650 / PowerVault 220S Performance issue

Trevor Cullingsworth trevor.cullingsworth at pleasant.net
Wed May 12 19:10:00 CDT 2004


Hi all,

Here is some background.  We have 2 PE 2650 servers and a PowerVault 
220S server.  Originally, we had a PERC3/DC card in each of our 2650s.  
We attached both servers to the PowerVault and ran in clustered mode.  
We were able to get everything set up and working fine.  We were going 
to use the PowerVault as our live website database running IBM DB2.  
However, after we got everything configured, we realized that the 
performance that we were seeing with I/O to the PowerVault was so poor 
that we would not be able to use it for our database.

I went through tech support with Dell and Red Hat and also left a post 
or two to this newsgroup.  The upshot was that we were told that the 
PERC3/DC card was no longer supported by Red Hat for our configuration.  
These cards were too unreliable.  According to Red Hat, the PERC4/DC 
card is the supported certified card for our configuration.  We took one 
of our 2650 servers and made this into our live database server with the 
databases installed on the local drives.  The other server is still 
attached to our PowerVault and it now has a PERC4/DC card installed.  I 
am running with the following:

--  PE2650 BIOS:  A17
--  PE2650 Baseboard firmware:  2.10
--  PE2650 primary backplane firmware:  1.01

--  Red Hat Advanced Server 3.0  kernel:  2.4.21-4.ELsmp

--  PERC4/DC  megaraid driver 2.00.5
--  PERC4/DC  firmware 1.92

--  PowerVault 220S  firmware:  1.4

We have 6 drives in the PowerVault running as a RAID5 with the sixth 
drive as a hot spare.  The drives are 72GB 15K drives.

I have 4 filesystems defined on the logical drive with each filesystem 
being approx. 50 GB each.

My tests show the following:

--  Writing a gig file to the local drive:                  40.3 MB/s

--  Writing a gig file to the PowerVault:                  6.6 MB/s
     Running in this configuration:
                    PERC4 set to Write-Through
                    PERC4 set to Direct I/O
                    PERC4 set to clustered mode
----------------------------------------------------------            
This represents about an 83% drop in performance.





--  Writing a gig file to the PowerVault:                  8.4 MB/s
     Running in this configuration:
                    PERC4 set to Write-Through
                    PERC4 set to Cached I/O
                    PERC4 set to clustered mode
----------------------------------------------------------            
This represents about an 79% drop in performance.





--  Writing a gig file to the PowerVault:                 71.7 MB/s
     Running in this configuration:
                    PERC4 set to Write-Back
                    PERC4 set to Direct I/O
                    PERC4 set to non-clustered mode
----------------------------------------------------------            
This is actually about a 43% increase in performance.

Unfortunately, to run the cards in clustered mode you have to have the 
write policy set to Write-Through.

I am going to reconfigure the logical ldrive on the PowerVault and just 
set up a 2 disk RAID-1 logical volume and see how perfomance is there.

But, in the meantime, has anyone had any success getting decent 
performance out of a PowerVault RAID system.  Or has anyone had any 
similar problems with a configuration like ours?

Are we using the PowerVault the correct way?  Maybe we should be using 
it as its intended function - as a doorstop? 

Just a little frustration getting through there.

If anyone has any tips or comments I would gladly welcome them.

Thank you.

TBC




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