Hello Narendra, On Tue, Aug 1, 2017 at 6:19 PM, Narendra Pal Singh < narendrapal2020@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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