[Gluster-devel] Decomission a brick

[Anand Avati]

DeeDee,
 decomissioning a brick is pretty much manual as of today. there are three
cases in which you are decomissinong - AFR, unify, stripe. I have explained
how I would decomission them. It is essential to understand the concept
rather than following the steps below as a 'tutorial', and find your own
(possibly much easier) procedure.

though the steps sound complex, if you look beyond the procedure, the idea
behind them is easy to understand.

the hot add/remove feature in the oncoming (1.4) release will do all this
for you automagically, this manual procedure is for 1.3.

 If it is a part of an AFR subvolume, just plug it out, trim your spec file,
and you are all set.

If it is a part of a unify subvolume,
 - remove the subvolume from the spec file,
 - flush your namespace cache,
 - remount your fs,
 - run a find /mnt/glusterfs for it to rebuild the ns cache (this time
without the contents of the brick to be removed since it is no longer in the
subvolume list)
 - rsync the export directory of the decomissioning brick onto the mount
point to merge back the contents.

If it is part of a stripe.
 the simplest is to move out just the striped files, re-do the config, and
write back the striped files freshly.
 another way is
 - declare a new stripe set, with a new export directory on the server,
excluding the decomissioning node.
 - load a unify on top of the old and new stripe, with 'switch' scheduler
and configure a directory to be forced onto the new stripe set.
 - copy within glusterfs, the old stripe files into the new directory
(mv/rename will not do) now all the striped files are restriped onto the new
volume
 - delete the old stripe files, essentially emptying the old stripe export
directories.
 - preserve only the first subvolume of the old stripe, and make that the
direct subvolume of the just-created unify.
 - get away with the old stripe volume.
 - done.

so.. that's the idea. do ask any questions if something is not clear.

avati

2007/12/8, DeeDee Park <deedee6905 at hotmail.com>:
>
>
> What is the procedure for removing a brick from operation without loosing
> any of the data while still
> providing an operational file system for the other users?
>
>
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-- 
If I traveled to the end of the rainbow
As Dame Fortune did intend,
Murphy would be there to tell me
The pot's at the other end.