On Mon, Feb 11, 2013 at 12:25:59PM -0800, Gregory Farnum wrote: > On Mon, Feb 11, 2013 at 10:54 AM, Kevin Decherf <kevin@xxxxxxxxxxxx> wrote: > > Furthermore, I observe another strange thing more or less related to the > > storms. > > > > During a rsync command to write ~20G of data on Ceph and during (and > > after) the storm, one OSD sends a lot of data to the active MDS > > (400Mbps peak each 6 seconds). After a quick check, I found that when I > > stop osd.23, osd.14 stops its peaks. > > This is consistent with Sam's suggestion that MDS is thrashing its > cache, and is grabbing a directory object off of the OSDs. How large > are the directories you're using? If they're a significant fraction of > your cache size, it might be worth enabling the (sadly less stable) > directory fragmentation options, which will split them up into smaller > fragments that can be independently read and written to disk. I set mds cache size to 400000 but now I observe ~900Mbps peaks from osd.14 to the active mds, osd.18 and osd.2. osd.14 shares some pg with osd.18 and osd.2: http://pastebin.com/raw.php?i=uBAcTcu4 -- Kevin Decherf - @Kdecherf GPG C610 FE73 E706 F968 612B E4B2 108A BD75 A81E 6E2F http://kdecherf.com -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
