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 VM Snapshots on the server that hosts SQL server
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shiyam198
Yak Posting Veteran

94 Posts

Posted - 09/17/2013 :  11:58:56  Show Profile  Reply with Quote
Hi,


We setup Windows Snapshots on the Windows Server (VM) that runs SQL server 2008.
It hosts databases for a reporting application. So, 90% of the queries are reads and the rest are writes to a log database.

I see significant slowness on this server after I restored the databases on the server. The queries (read) that usually take 1 to 4 seconds now take 35 seconds.

I see there is a snapshot setup on this server on the OS (Windows) level.
Could this be a reason?

Thanks for your input.

- Shiyam

tkizer
Almighty SQL Goddess

USA
37142 Posts

Posted - 09/17/2013 :  12:46:41  Show Profile  Visit tkizer's Homepage  Reply with Quote
I don't know anything about Windows snapshots, but I would take a step back. Have you checked the execution plan? Have you updated statistics on the tables? Is there a hardware bottleneck such as CPU or I/O? What do the wait stats show?

Tara Kizer
SQL Server MVP since 2007
http://weblogs.sqlteam.com/tarad/
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shiyam198
Yak Posting Veteran

94 Posts

Posted - 09/17/2013 :  14:14:05  Show Profile  Reply with Quote
I did check the Profiler and found the most expensive query on the web request. The same query that has the same version of the application and the databases runs in less than a second.

Even in this staging environment, I ran the test web request and it was much faster.

It is only after the restore of 2 databases (only one being the main dataastore) and a cube, it started being slow. from less than a second to 35 second.

Now if I restore the old databases that were on this server, it is still 35 seconds. Which means the issue is not on the databases, can't be on the server because before the restores it worked fine.

So, only thing I can think of it is the VM (Virtual Machine) snapshots that is kept for this Database server.

Am I wrong?

- Shiyam

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tkizer
Almighty SQL Goddess

USA
37142 Posts

Posted - 09/17/2013 :  15:06:42  Show Profile  Visit tkizer's Homepage  Reply with Quote
It did not mean that it's not the databases. Statistics! Update the statistics on the tables involved. How big are they? Maybe do a fullscan.

Tara Kizer
SQL Server MVP since 2007
http://weblogs.sqlteam.com/tarad/
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