Description of problem:
lvm2 tools don't support conversions to add/remove devices
to/from existing raid sets, e.g.:
'raid5' with 3 devices -> 'raid5' with 5 devices (i.e. from 2 stripes to 4 stripes)
In addition, restriping conversions from 'striped' with 2 stripes <-> 'raid4/5/6' with 4 stripes and back to 'striped' with now 4 stripes shall be supported.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. "lvconvert -i 4 $LV" on a 'striped' $LV
Changing the number of stripes on a 'striped' logical volume is not possible directly without the risk of data loss. It needs to be converted to at least 'raid4' or 'raid5' ('raid6' optionally) in order to take advantage of the resilient functionality in md raid and convert back to 'striped' after the addition of devices has finished reshaping. On the step from 'striped', a suitable number of raid image/metadata internal logical volume pairs have to be allocated for the additional stripes _and_ for the raid parity (plus for the q syndrome in case raid6 is being used to do the conversion).
The same shall be possible for 'raid0' once supported (see respective bzs)
Code's done and being reviewed/integrated.
Upstream commits e2354ea344c2 to 34caf8317243
For the release notes for 7.4, is it enough to say that you can now use the lvconvert command to add or remove devices from existing RAID logical volumes? Is there anything else a user needs to know here?
it's worth mentioning that the size of a RaidLV changes doing so.
I.e. the capacity always is 'N data stripes * image size' (lvconvert prompts and tells the user as much _before_ it converts adding/removing devices unless --yes is provided).
In case of image removal, --force is mandatory because shrinking comes with the inherent danger of data loss (user gets information of size before/after disk removal and he can lvextend before removing images unless he provided --force _and_ --yes when the conversion is carried out without prompting).
Could you review the release note description in the doc text? I didn't mention the prompts this command produces and how to avoid them, for the purposes of a release note summary.
(In reply to Steven J. Levine from comment #9)
> Could you review the release note description in the doc text? I didn't
> mention the prompts this command produces and how to avoid them, for the
> purposes of a release note summary.
Good as a release note. Not mentioning prompting is fine because we have -y/--yes globally described in the lvm man page.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.