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/images/feed-icon-10x10.jpg10f3ec5.jpg?uri=aHR0cHM6Ly93d3cubGlzdGJveC5jb20vaW1hZ2VzL2ZlZWQtaWNvbi0xMHgxMC5qcGc] <https://www.listbox.com/member/archive/rss/184463/25738179-216c4b5f> | Modify<https://www.listbox.com/member/?&;> Your Subscription [https://www.listbox.com/images/listbox-logo-small.png10f3ec5.png?uri=aHR0cHM6Ly93d3cubGlzdGJveC5jb20vaW1hZ2VzL2xpc3Rib3gtbG9nby1zbWFsbC5wbmc] <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
