On Fri, Mar 5, 2021, 6:18 PM Greg 'groggy' Lehey <grog@lemis.com> wrote:
On Friday,  5 March 2021 at 10:32:15 -0500, Theodore Ts'o wrote:
> On Fri, Mar 05, 2021 at 01:50:32AM -0800, John Gilmore wrote:
>> John P. Linderman <jpl.jpl@gmail.com> wrote:
>>> I have several 12 TB disks scattered about my house. 5% of 12TB is 600GB.
>> At one point in hystery, ext2 performance was reported to suffer badly
>> if there was less than 5% of disk space available in an active
>> filesystem.  My naive belief, probably informed by older and wiser heads
>> around Sun, was that when the file system was >95% full, ext2 spent a
>> lot of time seeking around in free lists finding single allocatable
>> blocks.  And there were no built-in "defragmentation" programs that
>> could easily fix that.
> I'll point out that BSD FFS, at least in BSD 4.3, reserves 10% of the
> file system for reserved blocks.

Oops, that's what I get for reading messages sequentially :-(  But in
this case it's for small values of 10.

We set this to 1% at Netflix and fill to about ~98-99% full over UFS. This works well as we don't have small files. SATA Flash we keep a bit more empty, but that's due to its crappy FLT liking more free space...


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