[EMAIL PROTECTED] uttered:
It takes at least two complete rotations of the disk platter
to do an atomic and durable commit. On a 7200 RPM disk, that
means 60 transactions per second is your speed of light.
Your question boils down to this: Can you speed up transactions
by dropping the durable property - the D in ACID. Yes you
can. Actually, most client/server database engines already
do this for you without telling you. Very few client/server
databases are really ACID - they are usually on ACI when
confronted with a power failure.
Are you sure about this? I'm pretty sure PostgreSQL is ACID by default,
and as certain as I can be without proof that the commercial (Oracle etc.)
are as ACID as the hardware they run on.
They achieve this by not requiring seeks to overwrite data, as the write
ahead log is sequential and so can be written at the sequential IO rate of
the underlying device in the best case.
The client/server databases are also not limited by the filesystem
synchronous metadata updates, and so are more likely to achieve the peak
IO rate of the underlying device.
[snip]
A second approach would be to overload the OS drivers on
the backend of SQLite to support asynchronous I/O. Mozilla
does this in Firefox in order to boost performance on NFS.
There is well-commented sample code showing how to do this
in the SQLite source file "test_async.c". That sample code
does not combine multiple transactions, but you could probably
tweak it to make that happen.
When doing some performance testing between different FS on Linux, I found
that Ext3 with "data=journal" option was about 50% faster than the next
fastest options (XFS and ext3 with "data=writeback"). Again, this is
because synchronous meta-data, as well as normal synchronous file data,
can be written sequentially in the FS journal at peak IO speed. If I can
find the figures, I'll post them. However, I mislaid the test results and
haven't got a suitable machine to reproduce at the moment.
--
D. Richard Hipp <[EMAIL PROTECTED]>
Christian
PS. If people are after maximum performance, I can recommend ext3 with
"data=journal" option for SQLite. The performance is stunning!
PPS. Merry Christmas to those so inclined.
--
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