The cluster is on nfs today, with 500gb NVME SiLOG. Under heavy IO the vm's are thrown into paused state instead of iowait. A prior email chain identified a code error in qemu, with a repro using nothing more than DD to set 2 gb on the virtual disk to 0's .
Since the point of the system is to handle massive IO workloads, this is obviously not acceptable. If there is a way to make the nfs Mount more robust I'm all for it over the headaches that go with managing block io. On Wed, Mar 2, 2022, 8:46 AM Nir Soffer <nsof...@redhat.com> wrote: > On Wed, Mar 2, 2022 at 3:01 PM David Johnson <djohn...@maxistechnology.com> > wrote: > >> Good morning folks, and thank you in advance. >> >> I am working on migrating my oVirt backing store from NFS to iSCSI. >> >> *oVirt Environment:* >> >> oVirt Open Virtualization Manager >> Software Version:4.4.4.7-1.el8 >> >> *TrueNAS environment:* >> >> FreeBSD truenas.local 12.2-RELEASE-p11 75566f060d4(HEAD) TRUENAS amd64 >> >> >> The iSCSI share is on a TrueNAS server, exposed to user VDSM and group 36. >> >> oVirt sees the targeted share, but is unable to make use of it. >> >> The latest issue is "Error while executing action New SAN Storage >> Domain: Volume Group block size error, please check your Volume Group >> configuration, Supported block size is 512 bytes." >> >> As near as I can tell, oVirt does not support any block size other than >> 512 bytes, while TrueNAS's smallest OOB block size is 4k. >> > > This is correct, oVirt does not support 4k block storage. > > >> >> I know that oVirt on TrueNAS is a common configuration, so I expect I am >> missing something really obvious here, probably a TrueNAS configuration >> needed to make TrueNAS work with 512 byte blocks. >> >> Any advice would be helpful. >> > > You can use NFS exported by TrueNAS. With NFS the underlying block size is > hidden > since direct I/O on NFS does not perform direct I/O on the server. > > Another way is to use Managed Block Storage (MBS) - if there a Cinder > driver that can manage > your storage server, you can use MBS disks with any block size. The block > size limit comes from > the traditional lvm based storage domain code. When using MBS, you use one > LUN per disk, and > qemu does not have any issue working with such LUNs. > > Check with TrueNAS if they support emulating 512 block size of have > another way to > support clients that do not support 4k storage. > > Nir >
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