Hey
Anyone on here who is knowledgeable about disk (free space) fragmentation (not
just opinionated ;)) ?
HFS+ is supposed to contain algorithms that limit file fragmentation, but
without a background process that moves files (or file blocks), it cannot
prevent free space fragmentation, just limit it. On a spinning disks that can
become a limit on performance (I presume that theoretically the same applies to
SSDs too) and any process that requires contiguous files will ultimately fail
if those cannot be obtained, regardless the underlying medium if it doesn't
take that aspect into account.
One way free disk space can become fragmented is when installing files in
presence of a significant amount of temporary files, like a ${build.dir}.
Example: even without the QtWebEngine component, Qt5's build directory takes up
about 6Gb when built with LTO (that same option will *decrease* the installed
footprint by a few percent). However, that same build directory decreases by
about 70% after running afsctool on it (if it weren't for a single static
library that's over 3Gb...)
I've added a post-build block that runs afsctool on ${build.dir} in some of my
ports (a parallelised version of afsctool I developed).
The question I'd like to raise is what the effect of that operation would be
when done systematically. The idea is of course to reduce port disk space usage
before creating the destroot directory. However, afsctool compresses copies of
files, for safety, so could actually be adding to fragmentation (esp. if run in
on multiple files in parallel).
Any thoughts on this, regardless of whether free disk space fragmentation is a
real-world issue or not?
Thanks,
René
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