Re: defragmenting best practice?

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2017-09-14 03:54, Duncan wrote:
> Austin S. Hemmelgarn posted on Tue, 12 Sep 2017 13:27:00 -0400 as
> excerpted:
> 
>> The tricky part though is that differing workloads are impacted
>> differently by fragmentation.  Using just four generic examples:
>>
>> * Mostly sequential write focused workloads (like security recording
>> systems) tend to be impacted by free space fragmentation more than data
>> fragmentation.  Balancing filesystems used for such workloads is likely
>> to give a noticeable improvement, but defragmenting probably won't give
>> much.
>> * Mostly sequential read focused workloads (like a streaming media
>> server)
>> tend to be the most impacted by data fragmentation, but aren't generally
>> impacted by free space fragmentation.  As a result, defrag will help
>> here a lot, but balance won't as much.
>> * Mostly random write focused workloads (like most database systems or
>> virtual machines) are often impacted by both free space and data
>> fragmentation, and are a pathological case for CoW filesystems.  Balance
>> and defrag will help here, but they won't help for long.
>> * Mostly random read focused workloads (like most non-multimedia desktop
>> usage) are not impacted much by either aspect, but if you're on a
>> traditional hard drive they can be impacted significantly by how the
>> data is spread across the disk.  Balance can help here, but only because
>> it improves data locality, not because it compacts free space.
> 
> This is a very useful analysis, particularly given the examples.  Maybe
> put it on the wiki under the defrag discussion?  (Assuming something like
> it isn't already there.  I've not looked in awhile.)
> 
I've actually been meaning to write up something more thoroughly about 
this online (probably as a Gist).  When finally get around to that 
(probably in the next few weeks), I'll try to make sure a link ends up 
on the defrag page on the wiki.