Thanks to both Brian and Andreas for the timely responses. Brian posed the question as to whether or not the OSTs were more or less balanced a week ago. The answer is that I believe that they were. Usually all OSTs report a similar percentage of usage (between 1% and 3% of one another). I believe that is why this new report piqued my curiosity.
Regarding Andreas remark about individual OST size, yes I understand that having larger individual OSTs can preempt any one OST from becoming so full that the others degrade in performance (per A. Dilger, not B. Murrel). For that reason I personally like the option available in newer Lustre releases (I think 1.8.x and higher) to allow up to 16Tb in a single OST slice. I know the previous limit was 8Tb per OST slice for precaution against data corruption. (I was able to build a larger OST slice with 1.6.7 but I was cautioned that some data may become unreachable and/or corrupted as the Lustre system had not at that time been modified to accept the larger partition sizes which the underlying files systems--ext4, xfs---would accept.) The OST formatted size of 6.3Tb fit nicely into the JBOD scheme of evenly-sized partitions. Thanks, megan On Tue, 2010-03-02 at 15:45 -0500, Ms. Megan Larko wrote: > Hi, Hi, > I logged directly into the OSS (OSS4) and just ran a df (along with a > periodic check of the log files). I last looked about two weeks ago > (I know it was after 17 Feb). Is the implication that at this point the OSTs were more or less well balanced? > Anyway, the OST0007 is more full than > any of the other OSTs. The default lustre stripe (I believe that is > set to 1) is used. Can just one file shift the size used of one OST > that significantly? Sure. As an example, if one had a 1KiB file on that OST, called, let's say, "1K_file.dat" and one did: $ dd if=/dev/zero of=1K_file.dat bs=1G count=1024 that would overwrite the 1KiB file on that OST with a 1TiB file. Recognizing of course that that would be 1TiB in a single object on an OST. > What other reasonable explanation for a > difference on one OST in comparison with the others? Any kind of variation on the above. > Could this cause > a lustre performance hit at this point? Not really. b. _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
