ITEM: AK2071L

Performance Tuning for Asynchronous I/O

Env: Model 7013-590 with 3.2.5

Desc:   Customer has a model 590 running Sybase using about 20 external
        drives.  He has turned on Asynchronous I/O on the recommendation
        of Sybase, but needs help configuring the different parameters.

        The default settings for aio which he is using are:

          MINIMUM number of servers                          [1]                       \#
          MAXIMUM number of servers                          [10]                      \#
          maximum number of REQUESTS                         [4096]                    \#
          server PRIORITY                                    [39]

        He is still seeing poor performance in the Sybase routines
        and would like to know how to tune these aio parameters.

        Customer was looking for a reference on this information. 

Action:

   Pointed him to the Performance Monitoring a Tuning Guide which 
   is part of the books on InfoExplorer ( CD version ) under
   the section:

        Performance Implications of Asynchronous I/O

   This document details that for systems with a high
   number of I/O requests the MAXIMUM number of servers should
   be set to at least 10 times the number of physical drives on the 
   system the MINUMUM number of servers should be set to  half the
   MAXIMUM value. In this case, the customer has 15 physical disks;
   therefore, he should configure these parameters to:

        MAX>=150 ( or >= 10 * number of disks )
        MIN=75 ( or 1/2 of MAX )

Next:

Close.



Support Line: Performance Tuning for Asynchronous I/O ITEM: AK2071L

Dated: July 1995 Category: N/A

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