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5.4. ctdb
CTDB is a clustered database based on Samba's Trivial Database (TDB). The ctdb package is
a cluster implementation used to store temporary data. If an application is already using TBD for
temporary data storage, it can be very easily converted to be cluster-aware and use CTDB.
• When installing ctdb, the tdb-tools package needs to be installed manually. This dependency issues
will be addressed in a future release.
5.5. device-mapper-multipath
The device-mapper-multipath packages provide tools to manage multipath devices using the device-
mapper multipath kernel module.
• When using dm-multipath, if features "1 queue_if_no_path" is specified in /etc/
multipath.conf then any process that issues I/O will hang until one or more paths are restored.
To avoid this, set no_path_retry [N] in /etc/multipath.conf (where [N] is the
number of times the system should retry a path). When you do, remove the features "1
queue_if_no_path" option from /etc/multipath.conf as well.
If you need to use "1 queue_if_no_path" and experience the issue noted here, use dmsetup
to edit the policy at runtime for a particular LUN (i.e. for which all the paths are unavailable).
To illustrate: run dmsetup message [device] 0 "fail_if_no_path", where [device] is
the multipath device name (e.g. mpath2; do not specify the path) for which you want to change the
policy from "queue_if_no_path" to "fail_if_no_path".
• When a LUN is deleted on a configured storage system, the change is not reflected on the host. In
such cases, lvm commands will hang indefinitely when dm-multipath is used, as the LUN has
now become stale.
To work around this, delete all device and mpath link entries in /etc/lvm/.cache specific to the
stale LUN.
To find out what these entries are, run the following command:
ls -l /dev/mpath | grep [stale LUN]
For example, if [stale LUN] is 3600d0230003414f30000203a7bc41a00, the following results may
appear:
lrwxrwxrwx 1 root root 7 Aug
lrwxrwxrwx 1 root root 7 Aug
This means that 3600d0230003414f30000203a7bc41a00 is mapped to two mpath links: dm-4 and
dm-5.
As such, the following lines should be deleted from /etc/lvm/.cache:
/dev/dm-4
/dev/dm-5
/dev/mapper/3600d0230003414f30000203a7bc41a00
23
(BZ#526479
)
2 10:33 -/3600d0230003414f30000203a7bc41a00 --> -../dm-4
2 10:33 -/3600d0230003414f30000203a7bc41a00p1 --> -../dm-5
24
(BZ#419581)
ctdb
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