On 08/16/2016 04:55 PM, Marcy Cortes wrote: > Larry wrote: > "I would look at your backup mechanism and make sure it is compatible before > you commit to it." > > Thanks Larry, that answers that!!
A note about volume management: Btrfs can do multi-volume backing store. In English, a Btrfs filesystem can span multiple partitions, multiple logical volumes, or multiple LUNs, or multiple DASD, whatever. (Think *PVs* in the LVM sense.) This is appealing. Btrfs was criticized early on, that's a "layering violation <https://etbe.coker.com.au/2012/04/27/btrfs-zfs-layering-violations/>". Combining volume management with the filesystem creates a storage monolith. Some people aren't bothered. Maybe you're not either. But it bugs the snot outta me. On the other side, Btrfs does subvolumes. (Sort of like *LVs* in LVM land, but more tightly coupled with the monolith.) Here too, some like it. I don't. For a historical example of a tool/subsystem which stretched across too many layers, see EVMS <https://en.wikipedia.org/wiki/Enterprise_Volume_Management_System>. _LVM2 is a better tool for volume management._ Y'all have heard me rant against partitioning. I avoid partitioning now thanks to LVM. (LVs can grow or shrink. Harder to do with partitions.) A logical volume can house EXT2, 3, 4, Btrfs, XFS, VFAT, ISO9660, UDF, HFS, CMSFS*, swap, anything. Physical volumes (PVs) backing a volume group (VG) can be added, migrated, removed. (We say "drained" in mainframe speak.) Very nice! Btrfs can be made to play well in an LVM context. Watch out for the defaults. Keep it simple. Btrfs wants to show you what it can do, including PV and SV tricks. (Save it for the Olympics, please!) I've got one system with Btrfs snapshots creeping up constantly. My recommendation is that you implement LVM. Use it for (almost) everything. (Best to leave boot disks separate, outside of LVM, for a lot of reasons I won't enumerate.) Go ahead and do Btrfs but keep it in "just a filesystem" mode so you can switch when needed. In English, _force Btrfs to behave_ in your LVM environment. And avoid partitioning when it doesn't really buy you anything. (Too many layers. Too much kun-foo-zhun.) Keep it simple. *CMSFS ... okay ... you wouldn't normally want to put it in a logical volume, /but you could/. -- R; <>< ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
