touch-packages team mailing list archive

[Dimitri John Ledkov <launchpad@xxxxxxxxxxxx>]

This is not the only place where %-only based metric is not appropriate
for all sizes, the other one being default swap size is a simple
multiple of RAM still, despite extreme cases of RAM >> HDD (in e.g.
high-mem VM cases) and very fast HDD (e.g. NVMe drives or RAID-arrays
speed up with SSD cache layers).

Adding in that as well can eat up a lot of disk space, and at times even
expensive one.

Whilst we all agree that performance does degrade at the extremely full
disk-space, I don't buy that 51GB of free disk-space is degraded
performance given an e.g. RAID1 1TB filesystem and typical file-sizes /
extends. I'll poke cking, to check if he has performance degradation
results for various file-systems w.r.t. % filled for various max sizes.

5% is sensible and appropriate for a wide distribution of filesystem
sizes, but tiny disks may want more reserve and ditto large disks may
want less. Thus the calculated reserve shouldn't be a linear 5%, but
some non-linear distribution or scaled value.

One reasonable distribution algorithm for scaling disk-space limits (in
the context of nagios warning/critical levels monitoring) that I have
seen is implemented in checkmk project https://mathias-
kettner.de/checkmk_filesystems.html#H1:The df magic number . However,
the margins there increase too rapidly at the small disk-space sizes.
Thus further tweaking and/or different distributions would be needed.

Theodore, would you be open to having a tune option to make reserve
level adaptive rather than static %? (default would be static)

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Touch seeded packages, which is subscribed to e2fsprogs in Ubuntu.
https://bugs.launchpad.net/bugs/1340448

Title:
  5% reservation for root is inappropriate for large disks/arrays

Status in “e2fsprogs” package in Ubuntu:
  Confirmed

Bug description:
  mke2fs (and it's ext3 and ext4 analogs) still default to reserving 5%
  of the filesystem for root.  With the size of modern disks and arrays
  this isn't a terribly sensible default, e.g. if I have a 10Tb array,
  mke2fs will reserve 500Gb for root.

  Obviously this is both tunable at FS creation time and fixable after
  the fact but I still think we should try and improve the defaults.

  Given the size of modern disks, I think it'd make sense to either a)
  only reserve a smaller amount (e.g. 1%) or b) reserve n% if the
  filesystem is << NNN GB and otherwise reserve NN GB.

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