[Info-vax] Defrag utility needed on Integrity SSD-only configurations?

[Marc Van Dyck]

Rod Regier was thinking very hard :
> I'm trying to decide if it is important to get a Disk File Optimizer license 
> in this context:
>
> Any thoughts on the usefulness/liability of regular execution of a disk 
> defragmentation utility on OpenVMS executing on an Integrity server only 
> equipped with SSD mass storage?
>
> I grasp the liability of frequent defragmentation on an SSD accelerating wear 
> with little return.
>
> Just for reference/comparison purpose, MS Windows 10 occasionally defragments 
> SSD's on an as-needed basis.
>
> https://www.laptopmag.com/articles/defragment-hard-drive-windows

We are a shop configured exactly like you suggest. OpenVMS on Integrity
blades with all storage, system disks included, on 3PAR 8440 configured
exclusively with SSD storage units.

We run the defragmenter on all our systems, all our disks (all DSAxx
except quorum disks).

I also asked the same question a few years ago when we implemented 
this,
and got no really satisfying answer. So we decided to keep the
defragmenter running. It's not really an expensive license, either...

Sometimes, for no special reason, the defragment script of a disk fails
to run or to reschedule. And we clearly notice a degradation of
performance each time this happens, and this disappears as soon as
the defragmentation index of the disk comes back to something
reasonable.

I'm not able to explain why. This is purely empirical observation.

Now, I must say that our application is quite I/O intensive, with a lot
of indexed files activity. We also create tons of log files each day,
and those, unfortunately, can't be contiguously pre-allocated. On good
days, a disk can have a fragmentation index below 20 when just fresh 
out
of defragmentation, and already be above 80 less than 24 hours after.

-- 
Marc Van Dyck