On Sun, Jan 30, 2022 at 04:39:30PM -0500, Stuart D. Gathman wrote: > On Sun, 2022-01-30 at 11:45 -0500, Demi Marie Obenour wrote: > > On Sun, Jan 30, 2022 at 11:52:52AM +0100, Zdenek Kabelac wrote: > > > > > > > > Since you mentioned ZFS - you might want focus on using 'ZFS-only' > > > solution. > > > Combining ZFS or Btrfs with lvm2 is always going to be a painful > > > way as > > > those filesystems have their own volume management. > > > > Absolutely! That said, I do wonder what your thoughts on using loop > > devices for VM storage are. I know they are slower than thin > > volumes, > > but they are also much easier to manage, since they are just ordinary > > disk files. Any filesystem with reflink can provide the needed > > copy-on-write support. > > I use loop devices for test cases - especially with simulated IO > errors. Devs really appreciate having an easy reproducer for > database/filesystem bugs (which often involve handling of IO errors). > But not for production VMs. > > I use LVM as flexible partitions (i.e. only classic LVs, no thin pool). > Classic LVs perform like partitions, literally using the same driver > (device mapper) with a small number of extents, and are if anything > more recoverable than partition tables. We used to put LVM on bare > drives (like AIX did) - who needs a partition table? But on Wintel, > you need a partition table for EFI and so that alien operating systems > know there is something already on a disk. > > Your VM usage is different from ours - you seem to need to clone and > activate a VM quickly (like a vps provider might need to do). We > generally have to buy more RAM to add a new VM :-), so performance of > creating a new LV is the least of our worries. To put it mildly, yes :). Ideally we could get VM boot time down to 100ms or lower. -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab
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