What about compression and checksumming? Those also seem redundant inside the guest and could be turned off for better performance.
-Perttu On 17 Jun 2015 at 13:49:30, InterNetX - Juergen Gotteswinter ([email protected]) wrote: With with default Settings you will end up in Caching everything twice with ZFS inside the Guest. Either use some regular, legacy FS or change primary/secondarycache to Metadata only Am 17.06.2015 um 12:20 schrieb David Finster: > Hi Perttu > > We don’t run any Linux inside KVMs, but we do run a fair amount of > Windows. In general, your right in that running ZFS inside a KVM isn’t > going to get you any benefit and would probably be detrimental. It is > worth noting that all writes from inside a KVM are considered > synchronous anyway as far as the ‘zones’ pool is concerned. Any writes > that your guest does will be immediately committed to some disk (hence > the importance of an SLOG). > > ZFS snapshots are consistent when created, but I guess there is the > potential for some application inside the VM to have writes outstanding > when a snapshot is taken (through queued IO?). If that were the case, > then you would need some mechanism of notifying the application that > it’s about to be snapped to be completely safe. > > That being said, anything that uses a proper transaction log should be > fine. I’ve done snapshots of SQL and Exchange servers and > migrations/test emergency restores have been fine. Doing a snapshot of a > live VM and then bringing it up on another host is similar to it > experiencing a power failure, which is what the transaction logs are > designed to handle. > > As Ian mentioned, you might also be better off giving LX zones a go - > they are much friendlier to the host and no additional file systems are > involved. > > - Dave > >> On 17 Jun 2015, at 8:00 PM, Perttu <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hello SmartOS community, long time follower, first time poster here. >> >> What do you guys think are best practices regarding file systems in >> KVM Linux guests? >> >> Is it advisable to use ZFS inside guests? Wouldn’t it use double the >> memory for the same data? >> >> Or would using something like XFS or ext4 be better and perhaps tuning >> them to be more synchronous if crash resiliency is wanted? >> >> My main concern is data integrity if I snapshot and send the guest >> regularly to another host for disaster recovery. Performance is also >> important but I do have a slog device (S3700). >> >> Cheers, >> Perttu >> *smartos-discuss* | Archives >> <https://www.listbox.com/member/archive/184463/=now> >> <https://www.listbox.com/member/archive/rss/184463/25738179-216c4b5f> >> | Modify <https://www.listbox.com/member/?&;> Your Subscription >> [Powered by Listbox] <http://www.listbox.com/> >> > > *smartos-discuss* | Archives > <https://www.listbox.com/member/archive/184463/=now> > <https://www.listbox.com/member/archive/rss/184463/26910370-9cc4a721> | > Modify > <https://www.listbox.com/member/?&;> > Your Subscription [Powered by Listbox] <http://www.listbox.com> > ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/27159464-c7cd6100 Modify Your Subscription: https://www.listbox.com/member/?&; Powered by Listbox: http://www.listbox.com ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/25769125-55cfbc00 Modify Your Subscription: https://www.listbox.com/member/?member_id=25769125&id_secret=25769125-7688e9fb Powered by Listbox: http://www.listbox.com
