On Tue, Mar 3, 2009 at 10:13, Nikola Ciprich <extmaillist@xxxxxxxxxxx> wrote: > > Hi, > I think DRBD *MIGHT* be Your problem anyways... > Can You try repeating Your measurments with > no-disk-barrier, no-disk-flushes, no-disk-drain > options for Your drbd devices and report the results? > nik I'm running DRBD 8.0.14 (latest stable) and it appears that no-disk-drain and no-disk-barrier options aren't available, however with no-disk-flushes write performance to the drbd volumes (other than the kvm volume) is the same and write performance in kvm is also unchanged (~10MB/s in windows, ~30MB/s in Linux) > > On Mon, Mar 02, 2009 at 04:00:57PM -0500, Malinka Rellikwodahs wrote: > > On Mon, Mar 2, 2009 at 15:53, Mark van Walraven <markv@xxxxxxxxxxxxxxx> wrote: > > > On Mon, Mar 02, 2009 at 03:11:59PM -0500, Malinka Rellikwodahs wrote: > > >> when running with a raw disk image as a file or a raw disk image on an > > >> lvm vg, I'm getting very low performance on write (5-10 MB/s) however > > >> when using qcow2 format disk image the write speed is much better > > >> (~30MB/s), which is consistant with a very similar setup running > > >> kvm-68. Unfortunately when running the test with qcow2 the system > > >> becomes unresponsive for a brief time during the test. > > > > > >> The host is running raid5 and drbd (drive replication software), > > >> however performance on the host is performaning well and avoiding the > > >> drbd layer in the guest does not improve performance, but running on > > >> qcow2 does. > > >> > > >> Any thoughts/suggestions of what could be wrong or what to do to fix this? > > > > > > RAID1 has *much* better write performance. With striping RAIDs, alignment > > > is important. RAID controllers sometimes introduce hidden alignment > > > offsets. Excessive read-ahead is a waste of time with a lot of small > > > random I/O, which is what I see mostly with guests on flat disk images. > > > > > > With LVM, it pays to make sure the LVs are aligned to the disk. I prefer > > > boundaries with multiples of at least 64-sectors, which makes the LVM > > > overhead virtually disappear. I align the guest filesystems too, when > > > I can. > > > > > > I don't think DRBD has an effect on alignment, but you might look at > > > keeping the metadata on another drive. > > > > > > Block - rather than file - images are much faster. > > > > > > Hope this helps, > > > > It does, however unless I'm missing something the performance is being > > lost not in the lvm/raid/drbd config, because I'm using the same setup > > for other partitions which are used for data on the host and write > > performance to those drives is just fine. > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > ------------------------------------- > Nikola CIPRICH > LinuxBox.cz, s.r.o. > 28. rijna 168, 709 01 Ostrava > > tel.: +420 596 603 142 > fax: +420 596 621 273 > mobil: +420 777 093 799 > www.linuxbox.cz > > mobil servis: +420 737 238 656 > email servis: servis@xxxxxxxxxxx > ------------------------------------- -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
