Hi Chris,
Am 14.11.2025 um 11:42 schrieb Chris Wright:
<snip detailed description>
all seems well for a time then throughput drops to essentially zero
The time things go well -- can you more or less reproduce that, or can
you even identify time or number of bytes transferred beyond which
things slow down?
- SD1 will have a single CPU pegged at 100%, with minimal IO traffic
(both ops and bandwidth) from the open volume file, we will get spikes
of good speed but average throughput after leaving a job running for a
week is <1 MiB/sec.
- SD2 is quiet, happily handling normal backup jobs from other clients
with normal performance
If we start a second, parallel, copy job we get similar initially good
throughput then peg a second CPU on SD1 to 100% but there isn't exactly
a big jump in performance.
You could try to identify potential problem points by experimenting with
different job sizes, different directions, and different storage
targets. I like using FIFO storage backed by /dev/null plus a pool where
I disable cataloging of files. Just make sure you never send actual
backups there, or migration jobs...
There are no warnings/errors being logged and everything appears to be
"working", just glacially slow and apparently totally bottlenecked on
whatever that single CPU thread is doing with minimal reads from the
volumes.
Any suggestions on where to look for the root cause here?
Not quite a root cause, but I'd start with tracing the SD activities
and/or system calls. strace with time stamps in my experience can help a
lot in identifying underlying issues, but will probably create rather
unwieldy output.
So just a few suggestions how to investigate, nothing I can see that
would quickly fix the problem.
But let us know what you do and find!
Cheers,
Arno
Thanks
--
Chris Wright
Application Software Developer
<http://www.maglabs.net>
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Arno Lehmann
IT-Service Lehmann
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