Dear Cephalopodians, seeing the recent moves of major HDD vendors to sell SMR disks targeted for use in consumer NAS devices (including RAID systems), I got curious and wonder what the current status of SMR support in Bluestore is. Of course, I'd expect disk vendors to give us host-managed SMR disks for data center use cases (and to tell us when actually they do so...), but in that case, Bluestore surely needs some new intelligence for best performance in the shingled ages.
I had a quick look at the repository and could only make out that libzbc has
been added some years ago,
but no activity after this (also no tickets in the issue tracker). Is this
still something on the roadmap?
It would be wonderful for backup / archiving / mostly data ingest / cold
storage clusters to be able to use cheaper and larger disks once they become
available :-).
I'm still positively optimistic for such use cases even though my personal
experience with SMR has not been so well up to now:
I bought a (not cleanly labelled...) DM-SMR, used it for BTRFS archiving
(btrbk, i.e. btrfs-send and -receive),
and after it was filled once, it got excruciatinly slow (less than a few kiB/s
even when changing only a few 100 MB after prolonged idle).
But then, deleting btrfs snapshots of a desktop OS is pure random read/write
access, and there are no optimizations for that use case in btrfs (and the
drive did not even support TRIM/DISCARD),
and I read on the btrfs list now that it can work well even in arrays mostly
used for cold storage if the balancing is throttled ;-).
Cheers,
Oliver
smime.p7s
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