On Thu, Jan 07, 2010 at 12:13:50AM +0000, Gordan Bobic wrote: > Paras pradhan wrote: > >I have a GFS based shared storage cluster that connects to SAN by fibre > >channel. This GFS shared storage hold several virtual machines. While > >running hdparam from the host to a GFS share, I get following results. > > > >-- > >hdparm -t /guest_vms1 > > > >/dev/mapper/test_vg1-prd_vg1_lv: > >Timing buffered disk reads: 262 MB in 3.00 seconds = 87.24 MB/sec > >--- > > > > > >Now from within the virtual machines, the I/O is low > > > >--- > >hdparm -t /dev/mapper/VolGroup00-LogVol00 > > > >/dev/mapper/VolGroup00-LogVol00: > > Timing buffered disk reads: 88 MB in 3.00 seconds = 29.31 MB/sec > >--- > > > >I am looking for possibilities if I can increase my I/O read write > >within my virtual machines. Tuning GFS does help in this case? > > > >Sorry if my question is not relevant to this list > > I suspect you'll find that is pretty normal for virtualization-induced > I/O penalty. Virtualization really, trully, utterly sucks when it comes > to I/O performance. > > My I/O performance tests (done using kernel building) show that the > bottleneck was always disk I/O (including when the entire kernel source > tree is pre-cached, with a 2GB of RAM guest. The _least_ horribly > performing virtualization solution was VMware (tested with latest player > 3.0, but verified against the latest server, too). That managed to > complete the task in "only" 140% of the time the bare metal machine did > (the host machine had it's memory limited to 2GB with the mem= kernel > option to make sure the test was fair). So, 40% slower than bare metal. > > Paravirtualized Xen was close behind, followed very closely by > non-paravirtualized KVM (which was actually slower when paravirtualized > drivers were used!). VirtualBox came so far behind it's not even worth > mentioning. > What, you're saying VMware Server (and player) were faster than Xen PV? I have hard time believing that.. based on my own experiences. -- Pasi -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
