New: [rhinstaller/blivet/pulls/215 master] Do not reserve extra space for metadata in a VG with RAID PVs

vpodzime installerbot-noreply at redhat.com
Wed Aug 26 12:22:24 UTC 2015


Reserving 5 extents per disk per LV for metadata if a VG is on top of RAID PVs
is a weird magic that saved us troubles with placing LVM on top of RAID, but
even on the first it's just wrong and doesn't make sense. LVM doesn't allocate
any extra meta data if an LV is added to a VG (unless it is a meta data LV of
course) and the RAID device below it (the PV) is just a block device with some
size and no matter how many disks are below, the meta data space used by LVM is
just subtracted from the RAID device's (PV's) size. Moreover the LVM extent size
has nothing to do with the RAID device so it's like mixing apples and oranges.

If things don't fit we need to tweak our calculations of free space/size in/of
an MD RAID device (depending on the level and underlying disks) since that's the
only place where these tweaks really make sense. However, after quite a lot of
testing it seems that we are reserving more than enough space for the meta data.
-- 
To view this pull request on github, visit https://github.com/rhinstaller/blivet/pull/215


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