We have been running KVM very successfully and I find ceph very interesting, I think a combination of ceph and linux scsi target with a scale out architecture is the future of storage in enterprise.
On Thu, Mar 27, 2014 at 10:57 PM, Shankhadeep Shome <shank15...@gmail.com>wrote: > Yes bcache will allow real time configuration of cache policies, there are > a lot of tunables. It allows a single cache device to map to multiple > backing devices. We are using bcache with LVM and linux scsi target to > implement the storage target devices. We use several of these devices to > export block devices to servers over fiber channel then use those block > devices as building blocks for local or distributed file systems.The > opennebula implementation was using glusterfs-fuse but we hope to > transition to native glusterfs with qemu. > > > On Wed, Mar 26, 2014 at 8:39 AM, Stuart Longland <stua...@vrt.com.au>wrote: > >> Hi Shankhadeep, >> On 26/03/14 12:35, Shankhadeep Shome wrote: >> > Try bcache as a flash backend, I feel its more flexible as a caching >> > tier and its well integrated into the kernel. The kernel 3.10.X version >> > is now quite mature so an epel6 long term kernel would work great. We >> > are using it in a linux based production SAN as a cache tier with pci-e >> > SSDs, a very flexible subsystem and rock solid. >> >> Cheers for the heads up, I will have a look. What are you using to >> implement the SAN and what sort of VMs are you using with it? >> >> One thing I'm finding: when I tried using this, I had a stack of RBD >> images created by OpenNebula that were in RBD v1 format. I converted >> them to v2 format by means of a simple script: basically renaming the >> old images then doing a pipe from 'rbd export' to 'rbd import'. >> >> I had a few images in there, most originally for other hypervisors: >> - Windows 2000 Pro image >> - Windows XP Pro image (VMWare ESXi image) >> - Windows 2012 Standard Evaluation image (CloudBase OpenStack image) >> - Windows 2008 R2 Enterprise Evaluation (HyperV image) >> - Windows 2012 R2 Data Centre Evaluation (HyperV image) >> >> The latter two were downloaded from Microsoft's site and are actually >> supposed to run on HyperV, however they ran fine with IDE storage under >> KVM under the out-of-the-box Ceph support in OpenNebula 4.4. >> >> I'm finding that after conversion of the RBDs to RBDv2 format, and >> re-creating the image in OpenNebula to clear out the DISK_TYPE attribute >> (DISK_TYPE=RBD kept creeping in), the image would deploy but then the OS >> would crash. >> >> Win2008r2 would crash after changing the Administrator password (hang >> with black screen), Win2012r2 would crash with a CRITICAL_PROCESS_DIED >> blue-screen-of-death when attempting to set the Administrator password. >> >> The other images run fine. The only two that were actually intended for >> KVM are the Windows 2012 evaluation image produced by CloudBase (for >> OpenStack), and the Windows 2000 image that I personally created. The >> others were all built on other hypervisors, then converted. >> >> I'm not sure if it's something funny with the conversion of the RBDs or >> whether it's an oddity with FlashCache+RBD that's causing this. These >> images were fine before I got FlashCache involved (if a little slow). >> Either there's a bug in my script, in FlashCache, or I buggered up the >> RBD conversion. >> >> But I will have a look at bcache and see how it performs in comparison. >> One thing we are looking for is the ability to throttle or control >> cache write-backs for non-production work-loads ... that is, we wish to >> prioritise Ceph traffic for production VMs during work hours. >> FlashCache doesn't offer this feature at this time. >> >> Do you know if bcache offers any such controls? >> -- >> 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 >> >> >> >
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