Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
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. -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. __ please don't Cc me, but send to list -- I'm subscribed