Hi Jaime, On 21/03/14 19:57, Jaime Melis wrote: > Have you benchmarked Online write-through caching / Online write-back > / Offline write-back ?
Benchmarked? I haven't even written the code yet. At the moment without caching I'm getting about 120MB/sec in my VMs when using virtio storage. I've been told by one of the would-be users that this is "unusably slow". Sébastian Han did some work with RBD+FlashCache here: http://www.sebastien-han.fr/blog/2012/11/15/make-your-rbd-fly-with-flashcache/ > Are you proposing we should allow the three options or just stick to one? > > Anyways, this sounds like an amazing addon :) Well, I can see cases where all three are useful. Production data workloads where data integrity is crucial, you'll want write-through caching. Speed-critical work loads, one of the write-back modes would be faster. Online write-back if you need live migration or don't have the space for offline write-back. > http://opennebula.org/addons/create/ > > It'd be nice if in the machine template where you specify individual > disks, if you could state what caching mode to use. Alternatives would > be to specify it in the image template or (least favourable) in the > datastore template. > > > If I understood correctly, you can use the CACHE option here: > http://docs.opennebula.org/4.4/user/references/template.html#persistent-and-clone-disks > > although it might need a change in order to be able to specify the > target cache. How do you think the interface should be? That looks more like how libvirt handles the cache to the back-end device. Then again, we're pretty much taking over whatever caching libvirt does and supplanting our own, so maybe it's appropriate to hijack that option and just tell libvirt to disable its cache. -- Stuart Longland Contractor _ ___ \ /|_) | T: +61 7 3535 9619 \/ | \ | 38b Douglas Street F: +61 7 3535 9699 SYSTEMS Milton QLD 4064 http://www.vrt.com.au _______________________________________________ Users mailing list Users@lists.opennebula.org http://lists.opennebula.org/listinfo.cgi/users-opennebula.org