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081308af30
We check the version number of dm-raid before testing certain
features to make sure they are present. However, this has
become somewhat complicated by the fact that the version #'s
in the upstream kernel and the REHL6 kernel have been diverging.
This has been a necessity because the upstream kernel has
undergone ABI changes that have necessitated a bump in the
'Y' component of the version #, while the RHEL6 kernel has not.
Thus, we need to know that the ABI has not changed but the
features have been added. So, the current version #'ing stands
as follows:
RHEL6 Upstream Comment
======|==========|========
** Same until version 1.3.1 **
------|----------|--------
N/A | 1.4.0 | Non-functional change.
| | Removes arg from mapping function.
------|----------|--------
1.3.2 | 1.4.1 | RAID10 fix redundancy validation checks.
------|----------|--------
1.3.5 | 1.4.2 | Add RAID10 "far" and "offset" algorithm support.
| | Note this feature came later in RHEL6 as part of
| | a separate update/feature.
------|----------|--------
1.3.3 | 1.5.0 | Add message interface to allow manipulation of
| | the sync_action.
| | New status (STATUSTYPE_INFO) fields: sync_action
| | and mismatch_cnt.
------|----------|--------
1.3.4 | 1.5.1 | Add ability to restore transiently failed devices
| | on resume.
------|----------|--------
1.3.5 | 1.5.2 | 'mismatch_cnt' is zero unless [last_]sync_action
| | is "check".
------|----------|--------
To simplify, writemostly/writebehind, scrubbing, and transient device
failure restoration are all tested based on the same version
requirements: (1.3.5 < V < 1.4.0) || (V > 1.5.2). Since kernel
support for writemostly/writebehind has been around for some time,
this could mean a reduction in the scope of kernels tested for this
feature. I don't view this as much of a problem, since support for
this feature was only recently added to LVM. Thus, the user would
have to be using a very recent LVM version with an older kernel.