SSD mode on hybrid disk (SSHD)

SSD mode on hybrid disk (SSHD)

[Federico Pedemonte]

Hi all,

I've replaced my notebook HDD with an SSHD hybrid disk (Seagate ST1000LM).
contrary to my experience with other similar machines, the disk
performance are really poor.

I suspect that it depends on btrfs detecting it as an SSD disk
(according to this dmesg message):

BTRFS: detected SSD devices, enabling SSD mode

is this the way it is supposed to be for hybrid disks?
is there a way to disable SSD mode (and, is it something I should try?)

thanks,
Federico

Re: SSD mode on hybrid disk (SSHD)

[Qu Wenruo]

> Hi all,
>
> I've replaced my notebook HDD with an SSHD hybrid disk (Seagate ST1000LM).
> contrary to my experience with other similar machines, the disk
> performance are really poor.
>
> I suspect that it depends on btrfs detecting it as an SSD disk
> (according to this dmesg message):
>
> BTRFS: detected SSD devices, enabling SSD mode
>
> is this the way it is supposed to be for hybrid disks?
> is there a way to disable SSD mode (and, is it something I should try?)
Hi,

You can try nossd mount option (mount DEV MNT -o nossd), which will 
disable ssd related optimization.

But according to my experience, even enable ssd mode on HDD, performance 
shouldn't drop too much, and sometimes, especially random write 
performance will even improve hugely.(but at cost of more fragments).

Thanks,
Qu

>
> thanks,
> Federico
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Re: SSD mode on hybrid disk (SSHD)

[Federico Pedemonte]

On Wed, Jun 10, 2015 at 9:47 AM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
> Hi,
>
> You can try nossd mount option (mount DEV MNT -o nossd), which will disable
> ssd related optimization.

thanks Qu!

I've tried it, but the disk still seems slow as hell.

> But according to my experience, even enable ssd mode on HDD, performance
> shouldn't drop too much, and sometimes, especially random write performance
> will even improve hugely.(but at cost of more fragments).

hum... ok!

so probably there are different issues to look at

thanks for your reply!

regards,
Federico