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Re: [Gluster-devel] How to make out-of-sync files visible in replication


From: Ian Rogers
Subject: Re: [Gluster-devel] How to make out-of-sync files visible in replication setup
Date: Thu, 25 Mar 2010 18:54:00 +0000
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This "directory of softlinks" would need more information in it to work I think.

Remember that the bricks know nothing of each other, and clients don't know what other clients get up to either.

Some random thoughts:

1. A client will be making a note like this when it's trying to write a file and spots that one of the replica sub-volumes is down 1.1. so the client shouldn't try to store this info in the sub-volumes as, by definition, they're in a degraded state. 1.2. the info should include which sub-volumes were up/down to help the clients make an informed decision for self-heal

that's as far as I got... ;-)

Ian

On 25/03/2010 09:12, Stephan von Krawczynski wrote:
Hello all,

during the latest discussion I always wondered how an admin of some
replication setup can find out easily if the glusterfs is in-sync or at least
mostly synced or which files are really out-of-sync without using getfattr on
_all_ files.
Since you can have millions of files it is obvious that ls -lR over the whole
tree has chances to never return because of the pure run time.
So it would be great to have some method of finding only the out-of-sync files
inside the glusterfs.
And exactly for that case I would like to make this proposal:
How about creating an option to specify a directory on each server, where the
server itself (i.e. glusterfsd) creates a softlink to every file he sets the
xattrs to a value that implies some of his fellow servers is out-of-sync.
As soon as this xattr gets cleared the softlink is removed.
Of course the softlink should point to the full path and not a relative one.
This would allow to get a replication in-sync simply by stating the files
pointed to by the softlinks.
I guess that this idea is easy to implement and trivial in usage. I hope my
explanation is good enough, if not feel free to ask anything.
What do you think?



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