Re:An Introduction to ZFS
by hardwaresofton on Friday November 20, 2020 @03:59AM
(#25158631)
Thanks for this -- I really haven't read all the BFS wiki and documentation just yet (since zfs was my first foray into this), will keep these points in mind. Don't think I've seen an "md" mentioned before...
md is the normal tool for doing RAID in software on Linux. It exposes a number of physical devices as one block device, which looks just like a normal hard disk.
btrfs is also a volume manager with RAID-like functionality of its own. But you can also use btrfs on an md device, just like you would with any other filesystem.
Software RAID is something I have only used for personal use, and with the enormous consumer hard drives available now, striping them seems less necessary than before.
Re:An Introduction to ZFS
by hardwaresofton on Friday November 20, 2020 @09:14AM
(#25160582)
Ahhhhh I though it was some sort of btrfs specific thing -- didn't recognize it as the 'md' in 'mdadm' (I've only dealt with software RAID before).
This is actually pretty interesting because one of the 'features' of the hosting provider I'm using is that they will software RAID your drives by default. Maybe btrfs is a better choice in that kind of environment if I don't have to undo the software raid on every machine and btrfs will interop well without too much abstraction.
Things to consider:
While a volume can span multiple devices (physical), historically it hasn't been the most stable and many users just stick with md, so real world testing is probably limited. Details are in the wiki.
When a volume starts getting full (let's say above 98% or something), performance suffers. This is also documented behaviour. Take monitoring seriously, even more than usual.
Pools and subvolumes can be a bit confusing at first, even if you've had experience with other volume managers. Read the documentation make sure you know what you're doing.