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I/O requests taking longer than 15 seconds? Expand / Collapse
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Posted Sunday, March 2, 2014 10:35 PM
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Hi,

Frequently reported in Error log file.

SQL Server has encountered 116 occurrence(s) of I/O requests taking longer than 15 seconds
to complete on file [E:\Program Files\Microsoft SQL Server
\MSSQL10_50.MSSQLSERVER\MSSQL\DATA\datafile.mdf] in database [DBNAME] (6).
The OS file handle is 0x0000000000000B30.
The offset of the latest long I/O is: 0x00000265590000

Generally Longer IO cause of Index fragementation is high. so configured Index rebuild on daily at off peak time then error was not reported at error log file and resolved. Before that I used rebuild index Management plan option on weekly basis.

I used customize index rebuild script by Mr. Michelle (http://sqlfool.com/). Thank you Michelle. It is very useful for biggest database.

http://www.sqlservercentral.com/Forums/Topic762772-146-2.aspx - there is one thread as Gila suggested, there is problem in IO subsystem at H/W side. Pls.suggestion me what are the points should be check at H/W?

Currently DB version: SQL 2K8R2 x64 bit with SP2, CU1.


Thanks
ananda
Post #1546779
Posted Tuesday, March 4, 2014 8:30 AM


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You need to check all the hardware and configurations. If you've never done that, I strongly recommend getting an expert in the door. Hardware configs, especially I/O, can be extremely tricky.

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Post #1547372
Posted Tuesday, March 4, 2014 2:08 PM


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As mentioned - there are plenty of different layers , possible reasons - I/O subsystem problems,I/O subsystem misconfiguration,Fragmentation,Excessive I/O requested by SQL Server,Inefficient placement of data files on disk

From SQL Server to disk there are plenty of different APIs to create this situation , for some extra details on mechanics , check this link

SQL Server - IO Requests taking longer than 15 seconds to complete

Troubleshooting the issue , particuarly in a shared environment , with shared services, SVC etc , SAN replication etc can be a challenge.


Jack Vamvas
sqlserver-dba.com
Post #1547554
Posted Tuesday, March 4, 2014 2:26 PM


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Grant Fritchey (3/4/2014)
You need to check all the hardware and configurations. If you've never done that, I strongly recommend getting an expert in the door. Hardware configs, especially I/O, can be extremely tricky.


I agree with Grant.

There are windows settings, nic settings, maybe HBA configurations, san configuration, network devices (possibly), network paths (bad cables can cause this), bad disks, overloaded buffer, etc etc etc.




Jason AKA CirqueDeSQLeil
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Post #1547566
Posted Wednesday, March 5, 2014 7:57 AM


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These can be the biggest problem to pin down the problem. If you have a SAN you need to get the SAN Admin involved. I have fought this many times and always I hear.. our SAN is running great.... one time I got Microsoft involved and all of the stuff we did with them they basically said the SAN is slow. Finally got the SAN folks to figure out it WAS the SAN causing the issues.


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