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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.
The mismatch count reported by a dm-raid kernel target used
to be effectively random, unless it was checked after a
"check" scrubbing action had been performed. Updates to the
kernel now mean that the mismatch count will be 0 unless a
check has been performed and discrepancies had been found.
This has been the intended behaviour all along.
This patch updates the test suite to handle the change.
- lvs -o lv_attr has now 10 indicator bits
- use '--ignoremonitoring' instead of the shortcut '--ig' used before (since
it would be ambiguous with new '--ignoreactivationskip')
Test the different RAID lvchange scenarios under snapshot as well.
This patch also updates calculations for where to write to an
underlying PV when testing various syncactions.
Assumed size of 4M was too large and the test was failing because
'dd' was failing to perform its write.
Calculate the size we need to write with 'dd' instead, so we
don't overrun the device.
aux updates:
prepare_vg now created clustered VG for cluster tests.
since dm-raid doesn't work in cluster, skip the cluster
test when someone checks for dm-raid target until fixed.
'lvchange' is used to alter a RAID 1 logical volume's write-mostly and
write-behind characteristics. The '--writemostly' parameter takes a
PV as an argument with an optional trailing character to specify whether
to set ('y'), unset ('n'), or toggle ('t') the value. If no trailing
character is given, it will set the flag.
Synopsis:
lvchange [--writemostly <PV>:{t|y|n}] [--writebehind <count>] vg/lv
Example:
lvchange --writemostly /dev/sdb1:y --writebehind 512 vg/raid1_lv
The last character in the 'lv_attr' field is used to show whether a device
has the WriteMostly flag set. It is signified with a 'w'. If the device
has failed, the 'p'artial flag has priority.
Example ("nosync" raid1 with mismatch_cnt and writemostly):
[~]# lvs -a --segment vg
LV VG Attr #Str Type SSize
raid1 vg Rwi---r-m 2 raid1 500.00m
[raid1_rimage_0] vg Iwi---r-- 1 linear 500.00m
[raid1_rimage_1] vg Iwi---r-w 1 linear 500.00m
[raid1_rmeta_0] vg ewi---r-- 1 linear 4.00m
[raid1_rmeta_1] vg ewi---r-- 1 linear 4.00m
Example (raid1 with mismatch_cnt, writemostly - but failed drive):
[~]# lvs -a --segment vg
LV VG Attr #Str Type SSize
raid1 vg rwi---r-p 2 raid1 500.00m
[raid1_rimage_0] vg Iwi---r-- 1 linear 500.00m
[raid1_rimage_1] vg Iwi---r-p 1 linear 500.00m
[raid1_rmeta_0] vg ewi---r-- 1 linear 4.00m
[raid1_rmeta_1] vg ewi---r-p 1 linear 4.00m
A new reportable field has been added for writebehind as well. If
write-behind has not been set or the LV is not RAID1, the field will
be blank.
Example (writebehind is set):
[~]# lvs -a -o name,attr,writebehind vg
LV Attr WBehind
lv rwi-a-r-- 512
[lv_rimage_0] iwi-aor-w
[lv_rimage_1] iwi-aor--
[lv_rmeta_0] ewi-aor--
[lv_rmeta_1] ewi-aor--
Example (writebehind is not set):
[~]# lvs -a -o name,attr,writebehind vg
LV Attr WBehind
lv rwi-a-r--
[lv_rimage_0] iwi-aor-w
[lv_rimage_1] iwi-aor--
[lv_rmeta_0] ewi-aor--
[lv_rmeta_1] ewi-aor--
New options to 'lvchange' allow users to scrub their RAID LVs.
Synopsis:
lvchange --syncaction {check|repair} vg/raid_lv
RAID scrubbing is the process of reading all the data and parity blocks in
an array and checking to see whether they are coherent. 'lvchange' can
now initaite the two scrubbing operations: "check" and "repair". "check"
will go over the array and recored the number of discrepancies but not
repair them. "repair" will correct the discrepancies as it finds them.
'lvchange --syncaction repair vg/raid_lv' is not to be confused with
'lvconvert --repair vg/raid_lv'. The former initiates a background
synchronization operation on the array, while the latter is designed to
repair/replace failed devices in a mirror or RAID logical volume.
Additional reporting has been added for 'lvs' to support the new
operations. Two new printable fields (which are not printed by
default) have been added: "syncaction" and "mismatches". These
can be accessed using the '-o' option to 'lvs', like:
lvs -o +syncaction,mismatches vg/lv
"syncaction" will print the current synchronization operation that the
RAID volume is performing. It can be one of the following:
- idle: All sync operations complete (doing nothing)
- resync: Initializing an array or recovering after a machine failure
- recover: Replacing a device in the array
- check: Looking for array inconsistencies
- repair: Looking for and repairing inconsistencies
The "mismatches" field with print the number of descrepancies found during
a check or repair operation.
The 'Cpy%Sync' field already available to 'lvs' will print the progress
of any of the above syncactions, including check and repair.
Finally, the lv_attr field has changed to accomadate the scrubbing operations
as well. The role of the 'p'artial character in the lv_attr report field
as expanded. "Partial" is really an indicator for the health of a
logical volume and it makes sense to extend this include other health
indicators as well, specifically:
'm'ismatches: Indicates that there are discrepancies in a RAID
LV. This character is shown after a scrubbing
operation has detected that portions of the RAID
are not coherent.
'r'efresh : Indicates that a device in a RAID array has suffered
a failure and the kernel regards it as failed -
even though LVM can read the device label and
considers the device to be ok. The LV should be
'r'efreshed to notify the kernel that the device is
now available, or the device should be 'r'eplaced
if it is suspected of failing.
