Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Lars Ellenberg wrote: > On Mon, Feb 09, 2009 at 10:35:44AM -0800, John Du wrote: > [...] > >>> 8.0.12 (2008-04-24) was the first release that could switch off this >>> additional reliability feature again, as it turned out that the >>> "better", more "advanced", IO subsystem you have, the worse the >>> performance impact is when turning on barriers/flushes. >>> >>> the options to do so are "no-disk-flushes" (backing store), >>> "no-md-flushes" (meta data store). >>> >>> in the 8.2 series, 8.2.6 (2008-05-30) is the first release >>> to support these keywords to switch off these additional >>> reliability features again. >>> >>> 8.2.7, and 8.3.0 again add some more advanced handling >>> for additional performance while maintaining reliability >>> when running on volatile caches. >>> >>> again, these features can be switched of. >>> >>> They should only be switched off if you run on a "safe" device >>> (non-volatile, battery backed cache -- or no cache at all). >>> >>> the important additional switch now is "no-disk-barrier". >>> >>> see also "man drbd.conf" >>> >>> all of this has _nothing_ to do with whether "iostats" shows >>> statistics for drbd or not. >>> >>> >>> >> Thank you Lars for your detailed explanation. I'll try the parameters >> you mentioned above. As I mentioned in my original message the process >> queue reaches 100 on this node when running 8.3 and it is under 1 with >> 8.2.0. >> >> I still do not understand why iostat only shows DRBD devices on this >> particular node with 8.2.7 and 8.3.0 but not other nodes with the same >> hardware, same Linux Kernel and same DRBD version. >> > > io stats accounting was introduced only in drbd-8.0.12 respective 8.2.6. > if you don't see drbd in iostats, you probably use an older DRBD version. > > I obviously did not make myself clear. We were running 8.3 on six nodes and only this node showed DRBD in iostat and only this node was having the problem I reported. I reverted to 8.2 on this node to make our production going. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20090209/1b56e7a6/attachment.htm>