Re: parity raid and ext4 get stuck in writes

quoted

[...] a long standing problem. When lots of writes to many
files are sent in a short time the kernel gets stuck and
stops sending write requests to the disks. [...] A simple way
to reproduce: expand a kernel source tree, like xzcat
linux-6.5.tar.xz | tar x -f -

That is a well known (ideally...) consequence of misconfiguring
both physical storage and the Linux flusher cache so there is a
high chance of post-saturation congestion under load.

https://www.sabi.co.uk/blog/anno05-4th.html?051105#051105

[...] I had two arrays with it, one on SSDs and one on HDDs.
The HDD array exhibited the problem almost exclusively [...]

If an HDD set is misconfigured so that it reaches post
saturation congestion of IOPS much sooner than problems with
that and the consequences of flusher cache misconfiguration will
happen much more frequently. Usually to sustain the same number
of workload IOPS one needs at least 10 times more HDDs than
SSDs.