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List:       gpfsug-discuss
Subject:    [gpfsug-discuss] what's on a 'dataOnly' disk?
From:       mark.bergman () uphs ! upenn ! edu (Mark Bergman)
Date:       2016-01-29 22:04:01
Message-ID: 20160129170401.0ec9f72e () uphs ! upenn ! edu
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What's on a 'dataOnly' GPFS 3.5.x NSD besides data and the NSD disk
header, if anything?

I'm trying to understand some file corruption, and one potential
explanation would be if a (non-GPFS) server wrote to a LUN used as a
GPFS dataOnly NSD.

We are not seeing any 'I/O' or filesystem errors, mmfsck (online) doesn't
detect any errors, and all NSDs are usable. However, some files seem to
have changes in content, with no changes in metadata (modify timestamp,
ownership), including files with the GPFS "immutable" ACL set.

If an NSD was changed outside of GPFS control, would mmfsck detect
filesystem errors, or would the GPFS filesystem be consistent, even
though the content of some of the data blocks was altered?

Is there any metadata or checksum information maintained by GPFS, or any
means of doing a consistency check of the contents of files that would
correlate with blocks stored on a particular NSD?


Thanks,

Mark


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