Re: defragmenting best practice?

[Duncan <1i5t5.duncan@cox.net>]

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.)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman