Olivier Gautherot wrote:
On Thursday 29 December 2005 18:34, Jerry McAllister wrote:
[...]
When you slice and partition the drive, there will likely be a handful
of sectors that don't round out to an even value so those are dropped.
Then, when you do the newfs, some space is taken by the spare superblocks
and finally the system reserves 8%. So, I would say you are getting
it all.
289GB is before the 8% reservation. I actually turned that off with tunefs.
I strongly suggest you do not do that - at least completely off.
Reduce it some, if you like, but keep some.
I too strongly recommend you keep these 8% in.
The fact is that the space is not wasted: in the old days, it was meant
to prevent the system from happily creating files until it dies - beyond
100%, files already opened could be written to but you could not create
new files. Some kind of "soft landing". I suppose it is still the case.
Actually, a friend asked me a few weeks ago how the file system could
reach 110% and he was speculating on how the system could use the
swap partition to get to this level: it was not the swap partition but this
extra space artificially held up.
You can safely and without afterthoughts let this 8% in.
In addition, there are some potentially undesirable side effects that
result from reduction - from the tunefs manpage discussing minfree:
<quote>
Note that lowering the threshold can adversely affect performance:
o Settings of 5% and less force space optimization to always be
used which will greatly increase the overhead for file
writes.
o The file system's ability to avoid fragmentation will be
reduced when the total free space, including the reserve,
drops below 15%. As free space approaches zero, throughput
can degrade by up to a factor of three over the performance
obtained at a 10% threshold.
</quote>
The first effect can be mitigated by specifying '-o time', but I always
leave it at the 8% default (fewer customizations for me to forget...).
Cheers
Mark
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