On Sat, 2011-01-22 at 11:23 +0100, Thomas Roth wrote: > > Btw, files on the MDT - why does the apparent file size there sometimes > reflect the size of the real file, and sometimes not?
I believe in the cases where you are seeing a size, it's SOM (size on mds) in action. > For example, on a ldiskfs-mounted copy of our MDT, I have a directory under > ROOT/ with > > -rw-rw-r-- 1 935M 15. Jul 2009 09000075278027.140 > -rw-rw-r-- 1 0 15. Jul 2009 09000075278027.150 Indeed. It's pretty hazy at the moment (so please do check the archives) but I think there was a thread here not that long ago that explained that SOM was only activated for newly created files in the release it showed up in. Now it's interesting that the two examples above have the same mtime. Perhaps there are conditions for recording an SOM for a preexisting file, like reading it perhaps. Maybe one of those has been read since you installed a SOM release and the other has not. > As they should, both entries are 0-sized, as seen by e.g. "du". Or ls -ls. > On Lustre, both files exist and both have size 935M. So for some reason, > one has a metatdata entry that appears as a huge sparse file, the other does > not. Right. > Is there a reason, or is this just an illness of our installation? As above, and per the archives. Cheers, b.
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