[RC5] AIX RC5 client

Joe Zbiciak j-zbiciak1 at ti.com
Tue Jul 21 09:31:51 EDT 1998


'simon at geordie.demon.co.uk' said previously:

[starting 8 clients sharing buff-in causes them to crack same block]

| 
| You need to make sure that they aren't using a checkpoint file, or make
| sure each checkpoint is pointed to a diferent file. Other than that, is
| should be OK.
| 

This isn't necessarily true.

When I was sharing buff-in files over NFS on some Solaris machines, if
two clients grabbed a block at the same time, sometimes they would grab
the same block.  There seemed to be some sort of race condition between
acquiring a lock on two different hosts for the same file.  Either
that, or the locking mechanism they are using doesn't work for NFS.

With this setup, I was duping a very large proportion of my blocks done
on these hosts (15-20%, IIRC).  Not good.  (Incidentally, since I was
using a fair number of hosts, I had checkpoint files turned off to keep
NFS traffic to a minimum, so that wasn't the problem.)

The only cure for me was to use separate buff-in files (a shared
buff-out is OK as long as only one client flushes).

If I were doing this today, I would set up a PProxy (now that they can
talk through firewalls) and set all the clients to buffer to memory,
buffering only 2 blocks (one being cracked, and one waiting "on
deck").

Regards,

--Joe

-- 
  +------- Joseph Zbiciak ------+
  |- - - j-zbiciak1 at ti.com - - -|  "The truth of a proposition has nothing
  | -Texas Instruments, Dallas- |   to do with its credibility.
  |- - #include <disclaim.h> - -|   And vice versa."       -- Lazarus Long
  +-----------------------------+

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