zfs discuss - Jan 2010 - Writing faster than storage can handle crashes system

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I''ve run up into yet another peculiarity while building my video
storage
solution on top of ZFS: if I fill up the disk to 98%, writes slow down -
this is expected. However, what happens when the write load overwhelms
the storage systems is puzzling to me. Instead of just blocking the
writer threads, the whole system''s memory usage also starts to spiral
out of control (and not by my processes, their VM usage remains
constant, as they simply start rejecting input if the writer threads
stall for too long). This process completely exhausts all physical
memory and starts swapping memory pages in and out, essentially bringing
the whole system to a screeching halt.

Even if I SIGKILL all the writing processes, they remain around as
zombies and the memory load continues to increase for quite some time,
often times still overwhelming the system - I can still see the disks
writing like crazy in iostat.

Is this behavior normal? What subsystems could be causing it? Or is it
totally unusual and should I be looking for it somewhere in my app?

BR,
- --
Saso
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