[IO Scheduler] : Query regarding Multi-Queue Block IO Queuing

[Arun Sudhilal]

Hello Narendra,

On Tue, Aug 1, 2017 at 6:19 PM, Narendra Pal Singh <
narendrapal2020 at gmail.com> wrote:

> Hello,
>
> I have a server with bunch of SSD and HDD. i want to enable blk-mq for
> SSDs only as it gives negative performance for rotational disks. (Please
> correct me here if i required)
>
> Is it possible to enable blk-mq for selective disks ?
>
SSD and HDD are two kinds of devices which should be handled by two
separate drivers. blk-mq is designed to exploit those IO controllers which
can handle multiple requests in parallel. Also blk-mq increases the
performance on devices where ramdom IO and sequencial IO performance
doesn't have much difference. blk-mq will still do a bit of IO reordering
to promote sequential access over random access. But since we have multiple
queues, the magnitude of reorder is low in blk-mq.

So to answer to your question. Ideally it might have taken care in the
drivers. No one will write a blk-mq model driver for HDD devices.

Regards,
Arun


> --
> Best Regards,
> Narendra Pal Singh
>
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