RE: SQL Server I/O performance issue

Giganews Newsgroups
Subject: RE: SQL Server I/O performance issue
Posted by:  Linchi Shea (LinchiSh…@discussions.microsoft.com)
Date: Mon, 24 Sep 2007

> Both % Disk Time and Avg Disk Queue Length are showing very poor
> performance compared to results shown when running the same test against the
> local disks. Average values are 10227 and 102 respectively.

These two counters are almost always useless. Check your disk latency (Avg
Disk Sec/Read and Avg. Disk Sec/Write) to see whether they are getting worse.

Linchi

"YaHozna" wrote:

> Hi. Wonder if anyone can offer me some advice?
>
> I'm currently involved in setting up some new kit prior to an upgrade of SQL
> Server 2000 Standard on a single Win 2000 server to SQL Server 2005 Standard
> x64 on a single node Failover Cluster. Additionally databases are to be held
> on FAS storage.
>
> Setting up has gone reasonably smoothly - SQL Server installed OK and
> failover is working fine. The only issue I've got is I/O performance between
> server and FAS which seems very poor compared to I/O on local machine. To
> stress test the setup I'm running SQLIOSim with the recommended config file
> for our setup and running Performance Monitor with the recommended
> Performance Audit counters. All results are fine except those for Physical
> Disk. Both % Disk Time and Avg Disk Queue Length are showing very poor
> performance compared to results shown when running the same test against the
> local disks. Average values are 10227 and 102 respectively. I'm not quite
> sure how to calculate the % Disk percentage however I think Avg Disk Queue
> Length is measured by dividing the value by the number of disks in the array
> - i.e. 20 in this case. This gives an average of approx 5 which, given that
> this is pretty much constant, would seem to suggest poor performance.
>
> So, finally, the question is, is there something fundamentally amiss with
> the setup or do the figures look OK? Any suggestions as to improving things
> or other stress tools/approaches to investigate?  The hardware spec is as
> follows:
>
> Each server has 1 NIC connected to a 1Gb Switch on a private LAN which is in
> turn connected to a NetApp file server.  Other NICs are for heartbeat and
> public LAN connection. All are using 1Gb Ethernet. iSCSI Initiator installed,
> v2.05.
>
> LUN created to the Netapp box of 100Gb - partitioned into 99Gb and 1Gb
> drives - Shows up as E: for data and Q: for quorum in Windows Explorer.
>
> N.B. Above info supplied by network guys and is stuff I'm not overly
> familiar with so be gentle with me :)
>
> Regards,
>
> YaHozna.

Replies

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In response to

SQL Server I/O performance issue posted by YaHozna on Thu, 20 Sep 2007