Re: mkfs.btrfs doesn't detect SSD

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-11-07 10:30, Christoph Anton Mitterer wrote:
> Hmm in fact it seems to be the kernel who wrongly, detects the type:
> /sys/block/sdb/queue/rotational = 1
> or more like the USB/SATA bridge simply reports it wrong.
>
> Anyway, is there a way to override? Or will setting
> /sys/block/sdb/queue/rotational = 0 give the expected behaviour?
This is a common issue with many USB/SATA bridges (and also 
device-mapper and MD devices), which don't properly query the attached 
device and modify the properties they report to the host system.  If you 
have some way to reliably identify this particular device, you could add 
a udev rule to automatically set it as non-rotational.  You could also 
do like you suggested and set it to non-rotational manually, although 
for mkfs at least, it's quicker to just manually specify '-m single'  on 
the command-line (that's the only difference in mkfs behavior for a 
SSD).  Like Chris said in his reply though, everything other than using 
single profile for metadata is done at mount time (if queue/rotational 
is 0, then -o ssd does get added to the mount options automatically, but 
it's a lot clearer to just specify the option yourself).


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