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

quoted

quoted

On 15 Jul 2016, at 19:29, Hendrik Friedel [off-list ref] 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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