Hello Tomasz,
thanks for your reply.
What disk are you using ?
It's a Seagate Expansion Desktop 5TB (USB3). It is probably a ST5000DM000.
There are two types:
1. SMR managed by device firmware. BTRFS sees that as a normal block device …
problems you get are not related to BTRFS it self …
That for sure. But the way BTRFS uses/writes data could cause problems
in conjunction with these devices still, no?
2. SMR managed by host system, BTRFS still does see this as a block device …
just emulated by host system to look normal.
I am not sure, what I am using. How can I find out?
In case of funky technologies like that I would research how exactly data is stored
in terms of “BAND” and experiment with setting leaf & sector size to match a
band,
Sorry, but I have no idea where to start.
It seems to me, although the drive being a pure consumer drive, it is a
'pro' feature and I should avoid it with BTRFS. I am just surprised,
there is no hint in the wiki with that regards.
Greetings,
Hendrik
> On 15 Jul 2016, at 19:29, Hendrik Friedel <hend...@friedels.name> wrote:
>
> Hello,
>
> I have a 5TB Seagate drive that uses SMR.
>
> I was wondering, if BTRFS is usable with this Harddrive technology. So, first
I searched the BTRFS wiki -nothing. Then google.
>
> * I found this: https://bbs.archlinux.org/viewtopic.php?id=203696
> But this turned out to be an issue not related to BTRFS.
>
> * Then this: http://www.snia.org/sites/default/files/SDC15_presentations/smr/
HannesReinecke_Strategies_for_running_unmodified_FS_SMR.pdf
> " BTRFS operation matches SMR parameters very closely [...]
>
> High number of misaligned write accesses ; points to an issue with btrfs
itself
>
>
> * Then this:
http://superuser.com/questions/962257/fastest-linux-filesystem-on-shingled-disks
> The BTRFS performance seemed good.
>
>
> * Finally this: http://www.spinics.net/lists/linux-btrfs/msg48072.html
> "So you can get mixed results when trying to use the SMR devices but I'd say
it will mostly not work.
> But, btrfs has all the fundamental features in place, we'd have to make
> adjustments to follow the SMR constraints:"
> [...]
> I have some notes at
> https://github.com/kdave/drafts/blob/master/btrfs/smr-mode.txt";
>
>
> So, now I am wondering, what the state is today. "We" (I am happy to do that;
but not sure of access rights) should also summarize this in the wiki.
> My use-case by the way are back-ups. I am thinking of using some of the
interesting BTRFS features for this (send/receive, deduplication)
>
> Greetings,
> Hendrik
>
>
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