[Bugs] [Bug 1637196] Disperse volume 'df' usage is extremely incorrect after replace-brick.

bugzilla at redhat.com bugzilla at redhat.com
Tue Oct 30 11:26:33 UTC 2018


https://bugzilla.redhat.com/show_bug.cgi?id=1637196



--- Comment #8 from Sanju <srakonde at redhat.com> ---
Updated reproducer:
1. create any type of volume which supports replace-brick operation, having at
least two bricks(B1, B2,..)
2. start the volume
3. mount the volume and check the volume size using df
4. perform a replace-brick operation on B1
5. check the size at mount point using df, it should be same as in step 3
6. perform replace-brick operation on B2.
7. check the size at mount point using df, it will be reduced by half

RCA:
While performing the replace brick operation we are not setting the fsid for
the new brick. So the new brick will have fsid as 0. when we perform 2nd
replace-brick operation, again the 2nd new brick will have fsid as 0. So, there
will be two bricks which have fsid as 0.

While calculating shared-brick-count, we consider the value of fsid of the
bricks. If bricks are having same fsid, that means they are sharing the same
file system. shared-brick-count refers to number of bricks that are sharing the
same file system. In this case, shared-brick-count becomes 2 (as both new
bricks are having fsid as 0). So, after 2nd replace brick operation the volume
size at the mount point will be reduced by half.

Thanks,
Sanju

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