GBAK is currently single threaded.

When I was working on a Gbak speedup project, 3-4 years ago, one of the
experiments we did was to thread Gbak. One thread for Database IO and one
thread for file IO (for the backup file) yielded a nice speedup, which
memory tells me was in the 20%-50% range. This never made it into
production as, at the time, too many InterBase supported platforms did not
support threads. Additionally, other work I did sped Gbak up by 30-40%
anyway.

The idea of multiple Gbak threads (both on the Database and Filesystem side)
is interesting -- and not too hard to implement if the database threads are
segmented on a table basis (Gbak will have to understand multi-file backups
in a different way than it's current mechanism as well).

There were other Gbak features spec'ed out that were never implemented --
such as "include set of tables" and "exclude set of tables" features (for
partial backups).

Additionally, I've always been enamored of using the database shadow
mechanism to make physical backup copies. There's a technique that works on
Unix (involving making multiple hard-links to the shadow file) - but fails
on NT, etc.

Dave


-----Original Message-----
From: Leyne, Sean [mailto:InterbaseArchitecture@...]
Sent: Wednesday, April 26, 2000 10:25 AM
To: IB-Architect@egroups.com
Subject: [IB-Architect] GBAK processing


Is GBAK (the backup process) a single threaded function, performing 1
task at a time, or is it multi-threaded?

Since I think the answer is that it is single threaded, I'll ask a
couple of other questions.

Would a multi-threaded backup process perform faster then the current
model?

What issue would prevent (or made very difficult) GBAK being made
multi-threaded?


I been thinking about a different approach to GBAK where it creates
treads (up to a certain limit) for each DB object to be backed up, with
these threads reading the DB information and building "backup
information" to be written out by a single "writer thread". I
understand that the system structure would need to be processed by a
single thread and written to disk before any application data.


Sean

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