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The HP Management Agents for VMware ESX Server 3.x include a Fiber Channel Agent (FCA agent) called cmafcad. If SCSI reservation conflicts on the ESX host are resulting in failed I/O or performance issues, it can be necessary to increase the polling interval of the Fiber Channel Agent. This can reduce the amount of SCSI reservation conflicts typical during peak business hours, VM startup, and VMotions.

Details
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The following can be seen in the /var/log/vmkernel file:

WARNING: SCSI: 5446: Failing I/O due to too many reservation conflicts
WARNING: SCSI: 5541: status 0xbad0022, rstatus 0xc0de01 for vmhba1:0:0. residual R 919, CR 0, ER 3
WARNING: Fil3: 1538: Failed to reserve volume


NOTE: 0xbad0022 translates to VMK_RESERVATION_CONFLICT per vmkerrcode.

Although reservation conflicts are not always an indication of an issue, large amounts of reservation conflicts resulting in failing I/O are, and should be addressed. There are many things that can contribute to reservation conflicts in a Virtual Infrastructure environment. Be advised that the following is only one possible solution to this issue. Other possible causes should be investigated.


Increasing the polling interval of the FCA agent can reduce SCSI reservation conflicts on the host by decreasing the amount of reservations required on a given LUN.


The following steps show the procedure for increasing the polling interval:


1. Login to the ESX server from an SSH client or from iLO.
2. Using an editor such as nano or vi, open the file /opt/compaq/storage/etc/cmafcad.
3. Change the polling interval from 15 seconds to a larger span, such as 60 seconds.


Look for the variable PFLAGS. By default, it looks like this: PFLAGS="-p 15 -s OK"
Change it to the desired value: PFLAGS="-p 60 -s OK"


4. Save the file, and exit from the editor.
5. Restart the management agents on the host. The following shows how this is done with the 8.0.0 Management Agents. See the appropriate documentation or man pages for later agents.

# service hpasm stop
# service hpsmhd restart
# service hpasm start

The new settings should be the following in a ps listing:

# ps -auxwww | grep cmafcad
root 14557 0.0 0.9 14676 2452 pts/1 S 18:31 0:00 cmafcad -p 60 -s OK