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<div>The underlying "lfs migrate" command (not the "lfs_migrate" script) in newer Lustre versions (2.9) is capable of migrating files that are in use by using the "--block" option, which prevents other processes from accessing or modifying the file during migration.</div>
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<div>Unfortunately, "lfs_migrate" doesn't pass that argument on, though it wouldn't be hard to change the script. Ideally, the "lfs_migrate" script would pass all unknown options to "lfs migrate". </div>
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<div>The other item of note is that setting the OST inactive on the MDS will prevent the MDS from deleting objects on the OST (see <a href="https://jira.hpdd.intel.com/browse/LU-4825">https://jira.hpdd.intel.com/browse/LU-4825</a> for details). In Lustre 2.9
and later it is possible to set on the MDS:</div>
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<div> mds# lctl set_param osp.<OST>.create_count=0</div>
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<div>to stop MDS allocation of new objects on that OST. On older versions it is possible to set on the OSS:</div>
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oss# lctl set_param obdfilter.<OST>.degraded=1</div>
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<div>so that it tells the MDS to avoid it if possible, but this isn't a hard exclusion.</div>
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<div>It is also possible to use a testing hack to mark an OST as out of inodes, but that only works for one OST per OSS and it sounds like that won't be useful in this case. </div>
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<div>Cheers, Andreas</div>
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On Mar 20, 2017, at 13:11, Brett Lee <<a href="mailto:brettlee.lustre@gmail.com">brettlee.lustre@gmail.com</a>> wrote:<br>
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<div>Hi Eli,<br>
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I believe that is still the case with lfs_migrate. If otherwise, we'll probably hear soon.<br>
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You should be able to disable those OSTs while keeping the file system active - via a command on the MDS(s) as well as the clients. My notes have the command as shown below, but please confirm via the appropriate Lustre manual:<br>
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lctl set_param osc.<fsname>-<OST00xy>-*.active=0<br>
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<div>Brett</div>
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<div class="gmail_quote">On Mon, Mar 20, 2017 at 10:43 AM, E.S. Rosenberg <span dir="ltr">
<<a href="mailto:esr+lustre@mail.hebrew.edu" target="_blank">esr+lustre@mail.hebrew.edu</a>></span> wrote:<br>
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<div>In the man page it says the following:<br>
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Because lfs_migrate is not yet closely integrated with the MDS, it cannot determine whether a file is currently open and/or in-use by other applications or nodes. That makes it UNSAFE for use on files that might be modified by other applications, since
the migrated file is only a copy of the current file, and this will result in the old file becoming an open-unlinked file and any modifications to that file will be lost.<br>
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Is this still the case?<br>
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Is there a better way to disable OSTs while keeping the filesystem live?<br>
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<div>Background:<br>
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<div>We need to take a OSS enclosure that hosts multiple OSTs offline for hardware maintenance, I'd like to do this without bringing Lustre as a whole down. I made sure there is enough space on the other OSTs to house the contents of the machine going offline
and am now about to move things.<br>
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Thanks,<br>
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Eli<br>
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