Re: ceph luminous bluestore poor random write performances

[Paul Emmerich <paul.emmerich@xxxxxxxx>]

Why do you think that is slow? That's 4.5k write iops and 13.5k read iops at the same time, that's amazing for a total of 30 HDDs.

It's actually way faster than you'd expect for 30 HDDs, so these DB devices are really helping there :)

Paul

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On Thu, Jan 2, 2020 at 12:14 PM Ignazio Cassano <ignaziocassano@xxxxxxxxx> wrote:

Hi Stefan, using fio with bs=64k I got very good performances.

I am not skilled on storage, but linux file system block size is 4k.

So, How can I modify the configuration on ceph to obtain best performances with bs=4k ?

Regards

Ignazio

Il giorno gio 2 gen 2020 alle ore 10:59 Stefan Kooman <stefan@xxxxxx> ha scritto:

Quoting Ignazio Cassano (ignaziocassano@xxxxxxxxx):
> Hello All,
> I installed ceph luminous with openstack, an using fio in a virtual machine
> I got slow random writes:
>
> fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test
> --filename=random_read_write.fio --bs=4k --iodepth=64 --size=4G
> --readwrite=randrw --rwmixread=75

Do you use virtio-scsi with a SCSI queue per virtual CPU core? How many
cores do you have? I suspect that the queue depth is hampering
throughput here ... but is throughput performance really interesting
anyway for your use case? Low latency generally matters most.

Gr. Stefan


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