I/O Error

  • I have a new Dell server and SAN setup as an active/passive cluster. Twice now the server hiccupped with the error below. My initial research seems to show this is a hardware error not sql server itself. Anyone else encountered this?

    SQL Server has encountered 1 occurrence(s) of I/O requests taking longer than 15 seconds to complete on file sql server 2005

  • Run a trace, find out what's taking that long.

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  • "SQL Server has encountered 1 occurrence(s) of I/O requests taking longer than 15 seconds to complete on file sql server 2005 "

    This can be the result of an autogrow occurring, so check the data files to insure that there is sufficient free space. Allocated size should be the sum of

    1 Used space

    2 the size of the largest table including indexes

    3 three to six months of growth.

    SQL = Scarcely Qualifies as a Language

  • Are you referring to free disk space for the mdf file? If so it has over 100 gig

  • Find out the disk response time across drives for these counters

    PHysical disk avg disk sec/ read, avg disk sec/ write and avg disk sec/ transfer, if the value continuoulsy sustains at or more than 0.020 Sec or 20 MilliSeconds (For SAN), this can be an issue either at switch or fabric or at SAN.Inform you our system/Server team and get them involved to get this resolved.

  • Thanks will try this, most of the articles tied to this error refere to the firmware on the RAID, it say MS put this in in sql 2000 SP4, but it is more related to system performance, not sql server itself

  • You might have a hardware problem somewhere. I've seen this error with those. I'd contact the vendor for the storage system and let them know you're getting this error.

  • For the drive with the mdf I am getting about .016

  • This data you have to collect for a prolonged duration across all drives also collect data for other counters for Object PhysicalDisk.

    Frequency of collection depends upon how frequently sql server is getting restarted, if it is pretty regularly then collect data for every 1 sec and then analyze it along with SAN Vendor and your system or server team to get it resolved.

    Analyze data, for before failure what are the counter values, based on that determine what are the processes that are running on SQL server.

    If nothing is going on from SQL Server side, are there any other applications running on sql server if not there are other servers that are configured to make use of SAN, so any one of the server which is doing high activity either at FAbric or switch or at SAN could cause this problem.

  • maybe you have already seen this, but i though why not post again:

    http://blogs.msdn.com/sqlserverstorageengine/archive/2006/06/21/642314.aspx

  • This just got posted today. Very useful

    http://blogs.msdn.com/psssql/archive/2008/07/08/sql-server-i-o-bottleneck-i-don-t-have-one-yes-you-do.aspx

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

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