One feature I think we would like to see that could benefit from LVM is some kind of multidisk support with better fault tolerance....
For example: Say you have a node, and there are 20 vm's on it, and thats all the disk io it could take. But say you have spare cpu/ram capacity other then the diskio being used up. It would be nice to be able to add a second disk, and be able to launch 20 more vm's, located on the other disk. If you combined them together into one file system (linear append or raid0), you could loose all 40 vm's if something went wrong. That may be more then you want to risk. If you could keep them as separate file systems or logical volumes (maybe with contigous lv's?) Each vm could only top out a spindle, but it would be much more fault tolerant to failures on the machine. I can see some cases where that tradeoff between individual vm performance and number of vm's affected by a device failure can lean in that direction. Thoughts? Thanks, Kevin ________________________________________ From: Premysl Kouril [[email protected]] Sent: Tuesday, January 19, 2016 4:40 AM To: OpenStack Development Mailing List (not for usage questions); [email protected] Subject: Re: [openstack-dev] [Nova] sponsor some LVM development Hi Matt, thanks for letting me know, we will definitely do reach you out if we start some activity in this area. To answer your question: main reason for LVM is simplicity and performance. 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. 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. 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 <[email protected]> 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: [email protected]?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: [email protected]?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
