MD and rotational attribute

MD and rotational attribute

[Karel Zak]

Hi Neil,

I guess that something is wrong with MD. If you create a RAID on ssd
(or scsi_debug in my example) than MD device is reported as rotational.
Simple example:

 modprobe scsi_debug dev_size_mb=500
 fdisk /dev/sdb
 ...
 mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb{1,2}

 # cat /sys/block/sdb/queue/rotational
 0
 # cat /sys/block/md0/queue/rotational
 1

It seems like a bug.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: MD and rotational attribute

[Martin K. Petersen]

>>>>> "Neil" == NeilBrown  <neilb@suse.de> writes:

Neil,

Neil> (I would say that the name 'rotational' is a bug - the issues here
Neil> is really whether seek is fast or slow is it not??... but no
Neil> matter).

Both the ATA and SCSI specs use the term 'rotational' which I guess is
how we ended up with that name.


Neil> What do you think Martin?  Should QUEUE_FLAG_NONROT move to
Neil> queue_limits much like QUEUE_FLAG_CLUSTER did?

Absolutely. I posted some patches converting both the nonrot and
discard/secure discard queue flags a while back but they didn't go
in. I'll freshen up the kit and resend...

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: MD and rotational attribute

[NeilBrown]

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On Sun, 26 Feb 2012 19:18:12 -0500 "Martin K. Petersen"
<martin.petersen@oracle.com> wrote:

> >>>>> "Neil" == NeilBrown  <neilb@suse.de> writes:
> 
> Neil,
> 
> Neil> (I would say that the name 'rotational' is a bug - the issues here
> Neil> is really whether seek is fast or slow is it not??... but no
> Neil> matter).
> 
> Both the ATA and SCSI specs use the term 'rotational' which I guess is
> how we ended up with that name.
> 
> 
> Neil> What do you think Martin?  Should QUEUE_FLAG_NONROT move to
> Neil> queue_limits much like QUEUE_FLAG_CLUSTER did?
> 
> Absolutely. I posted some patches converting both the nonrot and
> discard/secure discard queue flags a while back but they didn't go
> in. I'll freshen up the kit and resend...
> 

Thanks!

NeilBrown

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