From: kbrock@qcinet.Gwinnett.COM (Kevin Brock)
Newsgroups: comp.sys.hp
Subject: Processes staying blocked on inode
Keywords: INODE BLOCKING
Date: 2 Oct 92 20:14:50 GMT
Organization: Quality Consultants, Inc.

I have a client who is having a problem with some processes (background
reports) taking over all the disc I/O and leaving no available bandwidth to
others (foreground user processes).  This is an HP9000/847S with 96MB, disc
buffering set at the default of 10% (9800KB), HP-UX version 8.02 D, and 3
1.3GB drives.  The software that is running uses RM-Cobol almost
exclusively.  No other software is used, except that which is related to
system management (sar, cron, etc) and related to the accounting package
(sx200 - a faxing utility, and rarely, shell scripts).

What appears to be happening is that 2 or 3 background report processes, 
executed via "batch" (so, nice is set to 22), use about 95-100% of the disc
throughput capacity, leaving little to none available to on-line users.
I am getting this usage percent from both Glance and sar.  During peak times,
sar reports the disc usage at 99% for over an hour.  

Now, I know that during most of the life of this project, ALL of the data
file and RM-Cobol executables have been stored on the same disc drive, so
of course shifting these files onto the other 2 drives should help out.
But one of the big questions is that all has been going well this year
(startup was in Jan.) until someone filled up the drive early this month.
We have since freed up lots of disc space, but still we're not back to the
original performance levels.  Could something have gone wrong here?  Also,
the third drive was added this month.

Here's what we've tried so far... 
     1. Moved some of the files to another drive (mostly the work and
        spooling directories for reports since they seemed to be the ones
        taking using the disc capacity).

     2. I was suspecting the ninode kernel parameter as being too small,
        since glance was reporting many users blocking on inode.  (shows
        you what I know about HP-UX, ha! :-)

     (this weekend)...

     3. Spreading the actual data files between the 3 drives based on
        the usage; such as ledger on one (many reports are being run
        against these files), inventory and purchasing on another, and
        accounts payable and payroll on the third.  I hope that this will
        resolve the current critical problem.

There are several questions...

     As mentioned above, Could there be any connection between the disc
     being filled that one day and the performance hassles?  Could adding
     a 3rd drive caused worse performance (even though that drive was not
     being accessed)?

     Is there a way to limit a process from using >80% of the disc capacity
     by itself (such as nice is used to have some level of control on CPU
     usage)?  I know that one process did this for about an hour one
     morning, luckily few people were actually logged on at that time.

And one final point...

    Oh for an HP3000/9xx which uses dynamic caching and does a decent job
    of sharing resources to all users (not to mention volume management)!
-- 
Kevin Brock

kbrock@qcinet.gwinnett.com
{rutgers,ogicse,gatech}!emory!gwinnett!qcinet!kbrock