Re: Encrypted software RAID1 with Debian Stretch

On 13 Sep 2017, Wols Lists spake thusly:

On 13/09/17 14:52, Nix wrote:

quoted

Nonetheless, fs/ext2 is almost unmaintained these days, and bugs are
slowly creeping back in. fs/ext4 can take up its duties perfectly well
these days, reading and writing both ext4-sans-journal and traditional
ext2 filesystems perfectly well.

ext2 as filesystem code in linux no longer exists. Likewise, I believe,
ext3. Both have been dropped and deleted. The only supported/maintained
ext driver now is ext4, which has backwards compatibility with 3 and 2.

Oh! I failed to notice when that happened :)

... er, I just checked upstream master and ext2 still exists. ext3 was
removed in v4.3.

quoted

One person having no problems with a filesystem as new as btrfs does not
mean the filesystem is reliable enough to use for backup. The
reliability bar for such filesystems is far higher than that for fses in
daily use! ("The required-feature bar is often also much lower. All they
have to do is store stuff that rarely changes and not lose it!")

"The required-feature bar is often also much lower. All they
have to do is store stuff that rarely changes and not lose it!"

Actually, btrfs is very good at that! PROVIDED you don't use the fancy
new experimental features (like raid :-) in btrfs, it works very well.
It's a nice, stable, very decent filesystem.

I lost two btrfses via "it had lots of space, now it's saying -ENOSPC,
and now I can't mount it any more" bugs. Both were rapidly fixed, but
that sort of thing dents your confidence :) mind you that was a couple
of years back and these things do improve with time.

The rule is simple - don't abuse your tools, and btrfs - USED WITHIN ITS
LIMITATIONS - is a powerful and reliable file system.

Yeah, but... if you avoid the advanced features, why use btrfs? In
particular, why use it *for a backup medium* (where such features are
distinctly less useful than on a non-backup medium)?

-- 
NULL && (void)

On 14/09/17 12:08, Nix wrote:

quoted

The rule is simple - don't abuse your tools, and btrfs - USED WITHIN ITS

quoted

LIMITATIONS - is a powerful and reliable file system.

Yeah, but... if you avoid the advanced features, why use btrfs? In
particular, why use it *for a backup medium* (where such features are
distinctly less useful than on a non-backup medium)?

Because, if you use snapshots and an "in-place rsync" (which overwrites
the part of files which have changed, rather than replacing the file by
default), then each snapshot is a full backup, but only uses the space
of an incremental.

The OP was building a backup server, so all their live data is
elsewhere, and provided you look after your backups, this will give you
a very cheap and effective backup system.

(Add to which I know nothing about XFS and ZFS, other than ZFS needs
gobs of ram and why would you want to over-provision a server that isn't
switched on unless you're backing up.)

Cheers,
Wol