Phil Karn kirjoitti 2.5.2020 klo 10.20:
So I'm trying to figure out the advantage of including RAID 1 inside
btrfs instead of just running it over a conventional (fs-agnostic)
RAID subsystem.
I was originally really intrigued by the idea of integrating RAID into
the file system since it seemed like you could do more that way, or at
least do things more efficiently. For example, when adding or
replacing a mirror you'd only have to copy those parts of the disk
that actually contain data. That promised better performance. But if
those actually-used blocks are copied in small pieces and in random
order so the operation is far slower than the logical equivalent of
"dd if=disk1 of=disk2', then what's left?
Even the ability to use drives of different sizes isn't unique to
btrfs. You can use LVM to concatenate smaller volumes into larger
logical ones.
From the point of view of someone who has set up mdadm just twice and at
both times needed to start again at some point, due to messing something up,
I think one great point of Btrfs is ease of setting up. That's especially
true when adding or deleting disks semi regularly. I don't have any
experience with LVM, but adding it to the mix will probably complicate
things more.
There are, of course, lot of more or less "edge cases" that require knowing
things, or doing sufficient research before proceding. Like using replace
instead of add+delete. And if add+delete is requires (I recently replaced
6x4TB disks with 2x16TB in an array that also has 2x10TB and 2x8TB disk),
it's better to resize deleted disk in small increments instead of just
deleting (and I think adding some balance would help too, though I came up
with the idea too late), to avoid lot of unnecessary rewrites during delete,
and getting stuck with long running operation that can't be cancelled.
--
...Elämälle vierasta toimintaa...
Jukka Larja, Roskakori@xxxxxxxxxxxxxx
<saylan> I just set up port forwards to defense.gov
<saylan> anyone scanning me now will be scanning/attacking the DoD :D
<renderbod> O.o
<bolt> that's... not exactly how port forwarding works
<saylan> ?
- Quote Database, http://www.bash.org/?954232 -
