Date: Wed, 10 Jan 2007 23:21:01 -0500 From: John Nielsen <lists@jnielsen.net> To: freebsd-hackers@freebsd.org Subject: Best practices for using gjournal with gmirror? Message-ID: <200701102321.01562.lists@jnielsen.net>
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I have a few questions for pjd (or anyone else) about using gjournal, particularly when used with gmirror. 1) I'm running 6-STABLE and plan to test with gjournal6_20061030.patch (from the mailing list; updated version of 20061024 that applies cleanly). Is there a better/newer version for -STABLE that I should use instead? 2) When using gjournal and for a gmirror volume, does the journal need to be mirrored as well to maintain redundancy? If so, when storing the journal on the same physical disks as the mirror, is it better to mirror at the slice level (journal and fs on different partitions in the same mirror) or at the partition level (journal and fs each have their own mirror) or does it matter? 3) I remember reading where pjd said that gjournal plus gmirror or graid3 would eliminate the need to re-sync the array after a crash. While clearly a design goal, is that actually the case with the version of the patch mentioned above? If so, are any config changes needed or will it just happen automagically? 4) In the same vein as 3)--does a gjournal volume need to be fsck'ed after a crash? If not, will it just work (e.g. fsck -p sees that the filesystem is clean) or does it need to be disabled somehow? 5) Finally, how dangerous is this code? I realize it's experimental and only plan to use it with data that has recent backups, but how much should I worry about it blowing up my system or corrupting my files? Thanks! JN
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