[ZODB-Dev] Writeperformance for different storages

[Barry A. Warsaw]

>>>>> "TD" == Toby Dickenson <tdickenson@geminidataloggers.com> writes:

    TD> I know the BDB documentation says it is a good thing, but did
    TD> you measure whether the independant controllers actually made
    TD> a difference? to reads or writes? I would not expect that ZODB
    TD> (particularly under ZEO) has enough concurrency for this to
    TD> make a difference.

I had a dual scsi system for a short while and did a bunch of tests
including separating the log and data files.  This was primarily with
the loadmail tests which are more write intensive.  It made a huge
difference.  I'd need to do some digging to find the exact numbers but
IIRC there was a factor of 5-7 improvement (judicious tuning of other
available parameters may be part of that but not all).

Note that this wasn't with the current cvs of BDB.  I don't have
access to that dual scsi machine any more and my feeble hardware
attempts at trying to add a disk to my second IDE channel was less
than successful.  If anybody else has the h/w available, I could help
you reproduce the tests to see if we're still seeing that much
improvement.

    TD> (If it makes a difference for BDB, I might consider
    TD> resurrecting a plan to stripe a DirectoryStorage across
    TD> directories on multiple controllers)

Neat.

    TD> Its hard to imagine a storage writing any fewer bytes to disk,
    TD> or writing them in a way that is any faster to fsync. I think
    TD> FileStorage has unbeatable write performance.

Yep.
-Barry