[Gluster-users] A few queries on self-healing and AFR (glusterfs 3.4.2)
a.ghoshal at tcs.com
Mon Feb 2 18:30:15 UTC 2015
I have a replica-2 volume in which I store a large number of files that
are updated frequently (critical log files, etc). My files are generally
stable, but one thing that does worry me from time to time is that files
show up on one of the bricks in the output of gluster v <volname> heal
info. These entries disappear on their own after a while (I am guessing
when cluster.heal-timeout expires and another heal by the self-heal daemon
is triggered). For certain files, this could be a bit of a bother - in
terms of fault tolerance...
I was wondering if there is a way I could force AFR to return
write-completion to the application only _after_ the data is written to
both replicas successfully (kind of, like, atomic writes) - even if it
were at the cost of performance. This way I could ensure that my bricks
shall always be in sync.
The other thing I could possibly do is reduce my cluster.heal-timeout (it
is 600 currently). Is it a bad idea to set it to something as small as
say, 60 seconds for volumes where redundancy is a prime concern?
One question, though - is heal through self-heal daemon accomplished using
separate threads for each replicated volume, or is it a single thread for
every volume? The reason I ask is I have a large number of replicated
file-systems on each volume (17, to be precise) but I do have a reasonably
powerful multicore processor array and large RAM and top indicates the
load on the system resources is quite moderate.
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