Re: Recommended filesystem for RAID 6

[pg@mdraid.list.sabi.co.UK (Peter Grandi)]

>> [...] Note that it IS a shingled drive, so fine for backup,
>> much less so for anything else.

It is fine for backup especially if used as a tape that is say
divided into partitions and backup is done using 'dd' (but
careful if using Btrfs) or 'tar' or similar. If using 'rsync' or
similar those still write a lot of inodes and often small files
if they are present in the source.

>> I'm not sure whether btrfs would be a good choice or not ...

> [...] btrfs did NOT play well with raid 5/6. It may be old
> info, but:
> https://superuser.com/questions/1131701/btrfs-over-mdadm-raid6

That seems based on some misunderstanding: native Btrfs 5/6 has
some "limitations", like most of its volume management, but
running over MS RAID 5/6 is much the same as running on top of a
single disk, so fine. MD RAID 5/6 takes care of redundancy so
there is no need to have metadata in 'dup' mode.

Using RAID 5/6 with SMR drives can result in pretty huge delays
(IIRC a previous poster has given some relevant URL) on writing
or on rebuilding, as the "chunk" size is very likely not to be
very congruent with the SMT zones.