Troubleshooting
Problem
When resources are moved in a TSAMP environment there are entries in /var/log/messages to "reservation conflicts"
Resolving The Problem
The problem with the reservation conflicts is seen more often with multipath devices/drivers.
The problem may have various reasons, one of them could be the multipath driver itself. Basically it is tried to ensure that only one node has write access at the same time to the disks for data integrity.
One reason is the disk reservation of the TieBreaker when using SCSI TieBreaker.
Her a possible workaround is to use SinglePath devices instead
Another option could be to blocklist device:
For multipath drivers connecting to storage area networks (SAN), it is useful to blocklist devices in /etc/multipath.conf to blocklist devices. This prevents the multipath driver from attempting to use the device.
The RSCT IBM.Disk class devices have an attribute "DeviceLockMode" set to 1
(which means SCSI-2) and the disks itself use the value from that
IBM.Disk class.
It is possible to set attribute to 0 (Device locking disabled, no protection) to prevent writing the reservation conflict messages
It can be changed for all (on IBM.Disk class level) with
CT_MANAGEMENT_SCOPE=2
chrsrc -c IBM.Disk DeviceLockMode=0
or for a single disk
CT_MANAGEMENT_SCOPE=2
chrsrc -s 'DeviceName="/dev/sdb" ' IBM.Disk DeviceLockMode=0
where /dev/sdb is a sample device name
The default is DeviceLockMode=3 and means
"Device locking for the IBM.Disk resource is set to the value that is specified at the class level."
For more details and explanation see the RSCT Administration guide page 243 foll.
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Document Information
Modified date:
17 June 2018
UID
swg21683217