Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Wed, Jan 30, 2008 at 11:12:54AM +0000, Ben Clewett wrote: > > > Hi Lars, > > I am still having performance issues, ref DRBD locking. You were kind > enough to spend some time to worked out it was probably my underlying > storage at fault. > > I am using HP cciss P400 hardware RAID controllers. I have these in 12 > HP Proliant DL G5 servers, only four of these are on DRBD. These four > are the ones which suffer the problem. > > I have recently changed the read-ahead-buffer from the default 4 MB to > 512 KB. Therefore when the disk reads 1 or more bytes, it used to read > another 4 MB into cache, and now reads 512 KB. I can't take these > servers off line to rigorously test, but anecdotally this seems to have > made a difference for the better. > > I note my meta-disks are covered by this read-ahead-buffer. > > Do you think this might effect DRBD in some scenario? > > If you had to suggest a read-ahead-buffer size for the meta-disk, can > you suggest what might be optimum? since DRBD meta-data access most of the time is sinlge sector synchronous IO, read-ahead is completely irrelevant here. > > Thanks again for your excellent analysis, we also do support and consulting, you know :) -- : Lars Ellenberg http://www.linbit.com : : DRBD/HA support and consulting sales at linbit.com : : LINBIT Information Technologies GmbH Tel +43-1-8178292-0 : : Vivenotgasse 48, A-1120 Vienna/Europe Fax +43-1-8178292-82 : __ please use the "List-Reply" function of your email client.