What tests have you done exactly? I'll try to replicate them in my setup. FreeBSD also seemed slower to me, though I was more concerned with the network throughput, it struggles to saturate 1Gbps whereas linux ..just flies. I would have loved to be able to use pfSense more seriously, but performance sucked in a VM.
Lucian -- Sent from the Delta quadrant using Borg technology! Nux! www.nux.ro ----- Original Message ----- > From: "Logan Barfield" <lbarfi...@tqhosting.com> > To: dev@cloudstack.apache.org > Sent: Wednesday, 18 February, 2015 20:35:12 > Subject: Re: Libvirt & RBD caching > We're running FreeBSD with VirtIO. Disk is VirtIO in the libvirt > config, and shows up as a 'vtbd' device in /dev. I'm kind of stumped > on where the performance discrepancy could be coming from. > > Thank You, > > Logan Barfield > Tranquil Hosting > > > On Wed, Feb 18, 2015 at 3:23 PM, Wido den Hollander <w...@widodh.nl> wrote: >> >> >> On 18-02-15 21:00, Logan Barfield wrote: >>> Our current deployment is KVM with Ceph RBD primary storage. We have >>> rbd_cache enabled, and use "cache=none" in Qemu by default. >>> >>> I've been running some tests to try to figure out why our write speeds >>> with FreeBSD are significantly lower than Linux. I was testing both >>> RBD and local SSD storage, with various cache configurations. Out of >>> all of them the only one that performed close to our standard Linux >>> images was local SSD, Qemu cache=writeback, FreeBSD gpt journal >>> enabled. >>> >> >> I think the main problem is that FreeBSD uses ide/scsi and Linux uses >> VirtIO. >> >> Have you tried running FreeBSD 10 with the OS type set to Ubuntu for >> example? >> >>> I've been reading on various lists the reasons and risks for >>> cache=none vs cache=writeback: >>> - cache=none: Safer for live migration >>> - cache=writeback: Ceph RBD docs claim that this is required for data >>> integrity when using rbd_cache >>> >>> From what I can tell performance is generally the same with both, >>> except in the case of FreeBSD. >>> >>> What is the current line of thinking on this? Should be using 'none' >>> or 'writeback' with RBD by default? Is 'writeback' considered safe >>> for live migration? >>> >> >> None should still be ok, since librbd does the caching. It's not Qemu >> who does the caching. >> > > Wido
