Re: librbd 4k read/write?

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> This is an expected result, and it is not specific to Ceph. Any
> storage that consists of multiple disks will produce a performance
> gain over a single disk only if the workload allows for concurrent use
> of these disks - which is not the case with your 4K benchmark due to
> the de-facto missing readahead.

I don't think that affects writes.

> To allow for faster linear reads and writes, please create a file,
> /etc/udev/rules.d/80-rbd.rules, with the following contents (assuming
> that the VM sees the RBD as /dev/sda):

I think the OP didn't say that the client is a VM.  It might be, it might be a KRBD mount, it might be through CSI, we don't know.

I asked the OP privately if it's a VM because the first thing I check in this situation is libvirt / librbd throttling.  It sounds a *lot* like saturating an IOPS client throttle, something I've seen time and again in virtualization scenarios.

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