[master 3/21] Account for bigger LVM meta data due to alignment on MD RAID
vathpela
installerbot-noreply at redhat.com
Wed Oct 7 20:50:38 UTC 2015
From: Vratislav Podzimek <vpodzime at redhat.com>
As explained in the inline comment LVM aligns data and meta data according to
the underlying block device. In case of a MD RAID device where typically a
512KiB chunks are used, this may result in twice as big space allocated for meta
data as if a plain partition was used. Since the default size is 1 MiB, we can
safely just use a double size in case an MD RAID device is used as a PV because
we can be at most 1 MiB and thus one extent off in the end which is okay.
---
blivet/devices/lvm.py | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/blivet/devices/lvm.py b/blivet/devices/lvm.py
index 8047aec..3396a8a 100644
--- a/blivet/devices/lvm.py
+++ b/blivet/devices/lvm.py
@@ -354,8 +354,25 @@ def size(self):
""" The size of this VG """
# TODO: just ask lvm if isModified returns False
- # sum up the sizes of the PVs and align to pesize
- return sum((max(Size(0), self.align(pv.size - pv.format.peStart)) for pv in self.pvs), Size(0))
+ # sum up the sizes of the PVs, subtract the unusable (meta data) space
+ # and align to pesize
+ # NOTE: we either specify data alignment in a PV or the default is used
+ # which is both handled by pv.format.peStart, but LVM takes into
+ # account also the underlying block device which means that e.g.
+ # for an MD RAID device, it tries to align everything also to chunk
+ # size and alignment offset of such device which may result in up
+ # to a twice as big non-data area
+ # TODO: move this to either LVMPhysicalVolume's peStart property once
+ # formats know about their devices or to a new LVMPhysicalVolumeDevice
+ # class once it exists
+ avail = Size(0)
+ for pv in self.pvs:
+ if isinstance(pv, MDRaidArrayDevice):
+ avail += self.align(pv.size - 2 * pv.format.peStart)
+ else:
+ avail += self.align(pv.size - pv.format.peStart)
+
+ return avail
@property
def extents(self):
--
To view this commit on github, visit https://github.com/rhinstaller/blivet/commit/7ab2b801eddfeb468469c6e6815ba7862970f258
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