Comment by m4rtink
6 years ago
XFS on LVM thin pool LV should give you a very robust fs, cheap CoW snapshots, multi device support. If you want, you can make the thin pool be on RAID via LVM RAID under the thin pool.
For import export, IIRC XFS has support for it and you can dump/import LV snapshots to get atomicity.
For caching there is LVM cache, should be again possible to combine with thinpool & RAID. Or you can use it separately for normal LV.
All this is functionality tested by years of production use.
For compression/deduplication, that is AFAIK work in progress upstream based on the open sourced VDO code.
Interesting combination of tools I have used independently but never as a replacement of my beloved ZFS.
Never made snapshots with LVM. Always used LVM as a way to carve up logical storage from a pool of physical devices but nothing more. I need to RTFM on how snapshotting would work there - could I restore just a few files from an hour ago while letting everything else be as they are?
With ZFS, I use RAM as read chace(ARC) and an Optane disk as sync write cache(SLOG). I wonder if LVM cache would let me do such a thing. Again, a pointer for more manual reading for me.
Compression is a nice to have for me at this moment. Good to know that it is being worked on at the LVM layer.
IIRC you can mount any of the snapshots & copy files from it without influencing the others & the thin LV itself. As for RAM caching, I'm not sure LVM would allow LVM cache residing on ram disk PV, but isin't regular Linux transparent FS access RAM caching sufficient actually ?
For some reading about LVM thin provisioning:
http://man7.org/linux/man-pages/man7/lvmthin.7.html
https://access.redhat.com/documentation/en-us/red_hat_enterp...
Call me when somebody like a major cloud provider has used this system to drive millions of hard-drives. I'm not gone patch my data security together like that.
There is difference between 'all these tools have been used in production' and 'this is an integrated tool that has been used for 15+ years in the biggest storage installations in the world'.
Yes! The problem with the LVM approach trying to replicate anything ZFS is doing that you have to use a myriad of different tools. And then you have to pray that they all work correctly together, and if one has a bug you possible lost all your data because there may be so many data corruptions emerging because of it.