Dne 9.6.2016 v 22:24 Markus Mikkolainen napsal(a):
I seem to have hit the same snag as Mark describes in his post.
https://www.redhat.com/archives/linux-lvm/2015-April/msg00025.html
with kernel 4.4.6 I detached (--splitcache) a writeback cache from a mounted
lv which was then synchronized and detached. Then I reattached it and shortly
detached it again. What was interesting is that after the second detach it
synchronized AGAIN starting from 100% , and then I started getting filesystem
errors. I immediately shutdown, and forced an fsck , and didnt lose that much
data, but still had some stuff to correct.
It looked to me like a detached cache, being reattached will retain all cached
data on it, even though it was supposed to be written to the backing disk, and
then instead of marking it clean on attaching, it will continue serving old
data from the cache.
Yes - known issue, --splitcache is rather for 'debugging' purposes.
Use --uncache and create new cache when needed.
Splitted cache needs to be cleared on reattachment - but that needs further
code rework.
The idea behind is - we want to support 'offline' writeback of data as ATM
cache target doesn't work well if there is any disk error - i.e. cache is in
writeback mode and has 'error' sector - you can't clean such cache...
Regards
Zdenek
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