On Tue, 29 May 2012 10:33:52 +1000 Jonathan Molyneux <jonathan@xxxxxxxxxxxxxxxxxxxx> wrote: > Hi Everyone, > > I'm currently reshaping my raid5 array into a raid6 array (by adding a > spare and growing). > > Unfortunately I didn't research the nuances before doing so and missed > the opportunity to --layout=preserve. > > As a result the array is rebuilding by use of a backup-file, at a rather > slow pace. > > md1 : active raid6 sde1[0] sdb1[6] sdh1[5] sdc1[4] sdg1[3] sdd1[2] sdf1[1] > 7325679680 blocks super 0.91 level 6, 64k chunk, algorithm 18 > [7/6] [UUUUUU_] > [=========>...........] reshape = 47.0% (689413888/1465135936) > finish=4126.9min speed=3132K/sec > > I have tried the following so far: > > * read ahead tweaking > * stripe_cache_size tweaking (not a limiting factor - mdadm seems to > tune this appropriately) > * running the backup file from dev/shm (only for testing purposes) > > The reshape does not seem to be IO or CPU bound, it just seems to be > limited by the sync's and meta data updates to each disk. > > Is it possible to increase the buffer/stripes that mdadm process in a > batch to speed up the process (~41m/2 -> 1G) ? > > Any thoughts would be appreciated (even to confirm there is nothing to > be done). The only thing to do is to wait. This is very much a seek-bound operation and there is little room for making it go faster. In a few months we might see the need for the backup file disappear, which will improve things somewhat, but it will still be slowish. NeilBrown
Attachment:
signature.asc
Description: PGP signature
