Hi. Disk IO is related to background merge operations and this is normal.
What's not normal is that it is processing with a speed of just a few
megabytes per second.
It may indicate one of the following:
- faulty disks that need replacement (you can test them with "fio" or
similar); if the issue is happening on only one server out of many,
this is the case.
- very slow storage subsystem; if you are using small network disks in
the cloud, this may be the case and you need to provision more IO.
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