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LFS201 Chapter 15 I/O Scheduling


During the Video on Demo: I/O Schedulers, it was mentioned that normally a rotational will use io scheduler of deadline and an SSD will use cfq.

my rotational is 1 (spinner)
and my io scheduler is cfq.

I know he said this could change in the future, but i'm just wondering if I thru it off by using a VM instead of a local install of Ubuntu 18.04



  • lee42x
    lee42x Posts: 380

    Hello hroberts65616 ! No, you did not impact which schedulers are assigned to the disks as a VM. The IO schedules do change both in type and in implementation. Some distro's include all the schedules available at the kernel build time other distro's make some schedulers modules and do not load them by default. With VM's there is the added layer of the hypervisor that may have io scheduling as well as the client, giving two areas to tune. I generally set the VM client to "noop" and let$ cat the hypervisor deal with the IO scheduling.

    From my laptop:
    $ cat /sys/block/nvme0n1/queue/scheduler

    [none] mq-deadline bfq kyber

    Currently set to "none", see the kernel Docs for additional information on the specific IO scheduler.


  • coop
    coop Posts: 915

    recent redhat/centos doesn't even have cfq, and take bfq as default. This changes all the time.

    Note that with ssd I/O scheduling has lost a lot of its importance, wear leveling is much more important


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