@girish Here's what I found:
https://www.qwant.com/?q=long+run+copies+via+cp+causing+oom+memory
Various OOM workarounds:
https://github.com/rfjakob/earlyoom
https://github.com/hakavlad/nohang
https://github.com/facebookincubator/oomd
https://gitlab.freedesktop.org/hadess/low-memory-monitor/
https://github.com/endlessm/eos-boot-helper/tree/master/psi-monitor
Understanding OOM Score adjustment:
https://last9.io/blog/understanding-the-linux-oom-killer/
Possible LowFree issue:
https://bugzilla.redhat.com/show_bug.cgi?id=536734
Parallel vs sequential copy:
https://askubuntu.com/questions/1471139/fuse-zip-using-cp-reported-running-out-of-virtual-memory
And lastly, since you use stdio as output, perhaps it fills that up somehow. If it were redirected to disk it might be different.
That might also enable resuming a failed restore.
