On Tue, 2016-01-19 at 13:40 +0100, Premysl Kouril wrote: > Hi Matt, > > thanks for letting me know, we will definitely do reach you out if we > start some activity in this area.
You still haven't answered Anita's question: when you say "sponsor" do you mean provide resources to existing developers to work on your feature or provide new developers. > To answer your question: main reason for LVM is simplicity and > performance. Heh, this is history repeating itself from over a decade ago when Oracle would have confidently told you that Linux had to have raw devices because that's the only way a database will perform. Fast forward to today and all oracle databases use file backends. Simplicity is also in the eye of the beholder. LVM has a very simple naming structure whereas filesystems have complex hierarchical ones. Once you start trying to scale to millions of instances, you'll find there's quite a management penalty for the LVM simplicity. > It seems from our benchmarks that LVM behavior when > processing many IOPs (10s of thousands) is more stable than if > filesystem is used as backend. It sounds like you haven't enabled directio here ... that was the solution to the oracle issue. > Also a filesystem generally is heavier > and more complex technology than LVM and we wanted to stay really as > simple as possible on the IO datapath - to make everything > (maintaining, tuning, configuring) easier. And this was precisely the Oracle argument. The reason it foundered is that most FS complexity goes to manage the data structures ... the I/O path can still be made short and fast, as DirectIO demonstrates. Then the management penalty you pay (having to manage all the data structures that the filesystem would have managed for you) starts to outweigh any minor performance advantages. James > Do you see this as reasonable argumentation? Do you see some major > benefits of file-based backend over the LVM one? > > Cheers, > Prema > > On Tue, Jan 19, 2016 at 12:18 PM, Matthew Booth <mbo...@redhat.com> > wrote: > > Hello, Premysl, > > > > I'm not working on these features, however I am working in this > > area of code > > implementing the libvirt storage pools spec. If anybody does start > > working > > on this, please reach out to coordinate as I have a bunch of > > related > > patches. My work should also make your features significantly > > easier to > > implement. > > > > Out of curiosity, can you explain why you want to use LVM > > specifically over > > the file-based backends? > > > > Matt > > _____________________________________________________________________ > _____ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubs > cribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev