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From: | Zhang Huan |
Subject: | Re: [Gluster-devel] Question on choosing source of replica to heal with AFR |
Date: | Fri, 28 Feb 2014 15:39:21 +0800 |
Hi Zhang,On 02/28/2014 07:28 AM, Zhang Huan wrote:
Hello Ravi,
Thanks for your reply.
Sorry that I have a typo in my mail. It should by "underlying corruption" instead of "underlying correction".
I guess the logic of eliminating zero byte files from all innocent nodes is working for preventing underlying corruption to propagate to other brick. Asked in another way, if the underlying brick finds some file is corrupted, anything it could do to tell glusterfs to fix it?
If all nodes are innocent (from AFR's point of view) ,then AFR cannot use the changelog attributes to determine which is source. In this case, the safest bet is to mark all zero byte files as sink, so that we don't end up healing in the wrong direction. Like I said earlier, AFR can only use the changelog attributes (xattrs) to determine the source/sinks. It cannot detect underlying on disk file system corruptions outside the scope of the xattrs.
If you are sure that a particular brick is the right source despite the xattrs saying otherwise, you can manually change the attributes of the file on all bricks so that AFR now sees that brick as the source and heals in the expected direction.
-Ravi
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