I see the same issue in local scratch disk with scratchpad. I think qemu should block the io rather than pausing the VM.
On Thu, Sep 23, 2021 at 4:06 PM David Johnson <djohn...@maxistechnology.com> wrote: > I replaced the SSD intent log drive with an NVME drive, and the system is > much more stable now. > > *David Johnson* > *Director of Development, Maxis Technology* > 844.696.2947 ext 702 (o) | 479.531.3590 (c) > <https://www.linkedin.com/in/pojoguy/> > <https://maxistechnology.com/wp-content/uploads/vcards/vcard-David_Johnson.vcf> > <https://maxistechnology.com/> > > *Follow us:* <https://www.linkedin.com/company/maxis-tech-inc/> > > > On Thu, May 27, 2021 at 5:57 PM David Johnson < > djohn...@maxistechnology.com> wrote: > >> Hi ovirt gurus, >> >> This is an interesting issue, one I never expected to have. >> >> When I push high volumes of writes to my NAS, I will cause VM's to go >> into a paused state. I'm looking at this from a number of angles, including >> upgrades on the NAS appliance. >> >> I can reproduce this problem at will running a centos 7.9 VM on Ovirt 4.5. >> >> *Questions:* >> >> 1. Is my analysis of the failure (below) reasonable/correct? >> >> 2. What am I looking for to validate this? >> >> 3. Is there a configuration that I can set to make it a little more >> robust while I acquire the hardware to improve the NAS? >> >> >> *Reproduction:* >> >> Standard test of file write speed: >> >> [root@cen-79-pgsql-01 ~]# dd if=/dev/zero of=./test bs=512k count=4096 >> oflag=direct >> 4096+0 records in >> 4096+0 records out >> 2147483648 bytes (2.1 GB) copied, 1.68431 s, 1.3 GB/s >> >> >> Give it more data >> >> [root@cen-79-pgsql-01 ~]# dd if=/dev/zero of=./test bs=512k count=12228 >> oflag=direct >> 12228+0 records in >> 12228+0 records out >> 6410993664 bytes (6.4 GB) copied, 7.22078 s, 888 MB/s >> >> >> The odds are about 50/50 that 6 GB will kill the VM, but 100% when I hit >> 8 GB. >> >> *Analysis:* >> >> What I think appears to be happening is that the intent cache on the NAS >> is on an SSD, and my VM's are pushing data about three times as fast as the >> SSD can handle. When the SSD gets queued up beyond a certain point, the NAS >> (which places reliability over speed) says "Whoah Nellie!", and the VM >> chokes. >> >> >> *David Johnson* >> > _______________________________________________ > Users mailing list -- users@ovirt.org > To unsubscribe send an email to users-le...@ovirt.org > Privacy Statement: https://www.ovirt.org/privacy-policy.html > oVirt Code of Conduct: > https://www.ovirt.org/community/about/community-guidelines/ > List Archives: > https://lists.ovirt.org/archives/list/users@ovirt.org/message/TL22ZDND4FSV7RFSKPAWYJKBEBYV6AWC/ >
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