No disk activity during database restore

I am trying to restore a 200 GB database on to a newly formatted SAN
volume. The restore has been running for hours but there doesn't seem
to be a lot of disk activity on the disks I'm restoring to and I'm
wondering if that's anything to worry about.
Using perfmon I'm monitoring the % Disk time for the disk I'm restoring
to. It will show around 99% for a minute or so and then drop to zero
for 3-4 minutes. Is this normal? I know that since I'm restoring to a
new volume that SQL Server needs to zero out the 200 GB before it
starts the actual restore but I would expect to see 100% disk time
while it does this.
Any insight appreciated.
Thanks!Hi , Can you watch i/o in sysprocesses table for the SPID running the backup
task , this should be changing ...
Vishal
"pshroads@.gmail.com" wrote:
> I am trying to restore a 200 GB database on to a newly formatted SAN
> volume. The restore has been running for hours but there doesn't seem
> to be a lot of disk activity on the disks I'm restoring to and I'm
> wondering if that's anything to worry about.
> Using perfmon I'm monitoring the % Disk time for the disk I'm restoring
> to. It will show around 99% for a minute or so and then drop to zero
> for 3-4 minutes. Is this normal? I know that since I'm restoring to a
> new volume that SQL Server needs to zero out the 200 GB before it
> starts the actual restore but I would expect to see 100% disk time
> while it does this.
> Any insight appreciated.
> Thanks!
>|||Hi
I see this all the time. Even the IO stats and SPID stats show that nothing
is happening, but it is.
The issue is that before the actual restore can take place, the DB needs to
be created and initialized. This is an operation that SQL Server calls the
OS to do via an API. As the OS just indicates that the operation is still
running, the IO and SPID counter do not change.
The SAN has the instruction, and is doing the hard work. The OS and in turn
SQL Server are waiting for the SAN to finish.
If you were to have 200GB cache on the SAN, the SAN would return almost
immediately and then flush the pages to disk, but you probably don't have so
much, the disk IO is still happening at SAN level.
Deepening on the SAN configuration, 200GB could take anywhere from a few
seconds to a few hours.
Regards
--
Mike Epprecht, Microsoft SQL Server MVP
Zurich, Switzerland
IM: mike@.epprecht.net
MVP Program: http://www.microsoft.com/mvp
Blog: http://www.msmvps.com/epprecht/
"Vishal Gandhi" <VishalGandhi@.discussions.microsoft.com> wrote in message
news:007A4393-EE3D-4360-98B6-23A5C949FE17@.microsoft.com...
> Hi , Can you watch i/o in sysprocesses table for the SPID running the
> backup
> task , this should be changing ...
> Vishal
>
> "pshroads@.gmail.com" wrote:
>> I am trying to restore a 200 GB database on to a newly formatted SAN
>> volume. The restore has been running for hours but there doesn't seem
>> to be a lot of disk activity on the disks I'm restoring to and I'm
>> wondering if that's anything to worry about.
>> Using perfmon I'm monitoring the % Disk time for the disk I'm restoring
>> to. It will show around 99% for a minute or so and then drop to zero
>> for 3-4 minutes. Is this normal? I know that since I'm restoring to a
>> new volume that SQL Server needs to zero out the 200 GB before it
>> starts the actual restore but I would expect to see 100% disk time
>> while it does this.
>> Any insight appreciated.
>> Thanks!
>>|||Thanks for your reply. Even though SQL Server passes the task off to
the OS I'm still not sure why I don't see continual disk activity. Why
would I see a minute or two of activity followed by a few minutes of no
activity?
Thanks|||Hi
Have a look at the SAN management that your SAN vendor supplies. It will
give a you a good idea what is really happening in it.
Regards
--
Mike Epprecht, Microsoft SQL Server MVP
Zurich, Switzerland
IM: mike@.epprecht.net
MVP Program: http://www.microsoft.com/mvp
Blog: http://www.msmvps.com/epprecht/
<pshroads@.gmail.com> wrote in message
news:1119646132.436946.57570@.g14g2000cwa.googlegroups.com...
> Thanks for your reply. Even though SQL Server passes the task off to
> the OS I'm still not sure why I don't see continual disk activity. Why
> would I see a minute or two of activity followed by a few minutes of no
> activity?
> Thanks
>