High Read Disk Queue Length

  •  

    Recently we upgraded the RAM and OS to WIN 2003 , on our SQL Server Active/Active cluster  and after that we have been experiencing problems of  High Disk Queue Length. On investigation it was found that it is read disk queue length which is high.

    This is affecting our SQL Server Performance.

    No Changes has been made to the SQL Server in the upgrade process except for RAM , we have enabled awe memory and have specified the MAX size of memory.

    Is this a known issue/bug? Any ideas?

  • FOR example If you have 4 GM RAM in the server. Set the Fixed memory allocation for SQL server (AWE) to 3000 MB for example and leave the rest for OS and other applications in the server.

    Manian CSB


    csb manian

  • We have 12 GB of RAM on the server and we have fixed the SQL server memory at 5.5GB as it is a Active/Active cluster , so in case of a failover the total memory should not exceed 11GB on one node for both the instances.

  • Do you have /pae /3GB on the boo.ini and AWE enable on the SQL ?

  • Yes John we have that switch in boot.ini and also awe is enabled on the SQL server.

  • Hi,

    Since the performance problem seems to be related to

    Read only, try using profiler and check for long running queries or excessive table scans.

    If you are getting lots of table scans review your indexes and make sure your statistics are up to date.

    I hope this is of some help

    Brandon

  • Do you know the caching strategy on your controller ? Is paging size is et correct ?

  • All the queries and SP's are same as before as no chnage has been done to these. Regarding Caching we have read ahead caching at 0% on the controller and write back at 100%.

    Paging file is on a sep. drive of its own. !!!

  • How much memory are being used by SQL Server instances? Can you post the result of "select * from sysprocesses where waittime > 0 order by waittime desc"? If there are any queries running, verify whether they are running in parallel.

  • Sorry for the delay in replying. 

    Here is the result:

     

    6 0 0 0x0000 14437 RESOURCE_QUEUE                                                                                                                                                                                                                                                                  1 1 47 1 0 2004-03-23 21:33:00.980 2004-03-23 21:33:00.980 0 0 background                     0x0100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000                                                                                                                                                                                                                                                                            TASK MANAGER                                                                                                                                                                                                                                                                                                 sa                                                                                                                               0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0x0000000000000000000000000000000000000000 0 0

    4 0 0 0x0000 2375 RESOURCE_QUEUE                                                                                                                                                                                                                                                                  0 1 11047 0 0 2004-03-23 21:33:00.980 2004-03-23 21:33:00.980 0 0 background                     0x0100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000                                                                                                                                                                                                                                                                            LOCK MONITOR                                                                                                                                                                                                                                                                                                 sa                                                                                                                               0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0x0000000000000000000000000000000000000000 0 0

    65 4080 0 0x0042 625 SLEEP                                                                                                                                                                                                                                                                  1 1 2281 4 4 2004-03-26 09:32:06.097 2004-03-26 09:33:58.817 0 0 runnable                       0x8A56BBF9E63CAE409FC927D3DB59F34E00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 MIS156277                                                                                                                        SQL Profiler                                                                                                                     2604     SELECT                                                                                                                                                                                                                                                                             00096B5A6BA2 TCP/IP       msoni                                                                                                                            0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0x02000100579A5A62000000000100000000000000 164 -1

    1 0 0 0x0000 546 SLEEP                                                                                                                                                                                                                                                                  0 1 6078 0 0 2004-03-23 21:33:00.980 2004-03-23 21:33:00.980 0 0 background                     0x0100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000                                                                                                                                                                                                                                                                            LAZY WRITER                                                                                                                                                                                                                                                                                                  sa                                                                                                                               0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0x0000000000000000000000000000000000000000 0 0

    5 0 0 0x0422 359 PAGEIOLATCH_SH 5:1:15 5 1 954578 5081 0 2004-03-23 21:33:00.980 2004-03-23 21:33:00.980 0 0 background                     0x0100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000                                                                                                                                                                                                                                                                            AUTOSHRINK                                                                                                                                                                                                                                                                                                   sa                                                                                                                               0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0x0000000000000000000000000000000000000000 0 0

    62 3128 0 0x0042 281 OLEDB MISSQLVS09\PINTSQL09 (SPID=70) 10 5 109 6 19 2004-03-26 13:43:39.083 2004-03-26 13:43:54.180 0 0 runnable                       0x1C88C4C8DAAD094B99E242CFCBB2970600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 MISWEB10                                                                                                                         Microsoft(R) Windows (R) 2000 Operating System                                                                                   4144     SELECT                                                                                                                                                                                                                                                                             000BCD1A3C99 TCP/IP       newhire                                                                                                                          0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0x01000A00BF33952F98601C3A0000000000000000 0 -1

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