Re: High priority I/O with IFS MOV

Customer has a process that accepts many (and I mean MANY) PDFs into the
iFS every day. During the month they go into a directory such as
'/www/zendsvr6/pdfdocs/abchst'. They are referenced by the web server.
They are PDFs and never, ever changed or deleted.

BUT at the end of the month they are moved by month into a dir like:
'/www/zendsvr6/pdfdocs/abchsta/2016/11/'

They are moved one at a time because there is a control file with all the
names AND the process runs while the system is still up. The process uses
the MOV command to move the documents.

In the past this worked great (for years now) and now on shiny new Power8
it is very very slow. HOWEVER One other thing has changed.

The target directory ('/www/zendsvr6/pdfdocs/abchsta/') is now mounted in
a user ASP. That ASP is on larger slower disks. This makes perfect sense
because those documents are rarely if ever read and never go away. Total
document count is approaching triple digit millions in there. Normal busy
level on those disks approaches zero, all reads. There are thirty (30)
disks in ASP(2).

Now if it was only slow I would say: "Well yeah! It's actually COPYING and
DELETING the documents now because they are moving from *SYSBAS to ASP 2,
onto physically different disks, and they are slower." This would make
perfect sense and actually we wouldn't care much. The process changes the
control file as it goes so anyone looking them up gets the document whether
it has moved or not.

The problem is it's killing system performance overall. Even though this
process is running at priority 80 if you watch WRKSYSACT it constantly is
swapping to priority TEN (10). Overall cpu is well below 30% (of four
cores). There is a large amount of faulting and paging as well which I
think would be expected since all the documents are actually being copied.
The job currently run in a separate subsystem but is using *BASE memory.
*BASE is 1/4TB of memory.

Any thoughts on how to reduce the impact to the system here? Would a CPY
followed by a DEL be better than a MOV?

Would reducing the jobs timeslice help? It's at default of 5000.

--

- Larry "DrFranken" Bolhuis

www.Frankeni.com
www.iDevCloud.com - Personal Development IBM i timeshare service.
www.iInTheCloud.com - Commercial IBM i Cloud Hosting.
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