> fsync is enabled by default. fsync flushes disk buffers after every
> write. Turning it off lets the OS flush buffers at its leisure.
setting
> fsync=false will often double the write performance and since writes are
> running faster, there's more bandwidth for the reads as well, so
> everything goes faster.
"doubling performance" is very conservative, I've seen it give more than
a tenfold increase in performance on large insert/update batches. Of
course, the exact figure depends on a lot of hardware and OS factors.
> Definitely look at putting your data onto a Ultra160 SCSI 15krpm RAID1
> set. My dual 80 Gig Ultra100 IDEs can get about 30 Megs a second in a
> RAID1 for raw reads under bonnie++, while my pair of Ultra80 10krpm 18
gig
> scsis can get about 48 Megs a second raw read.
If you trust the hardware, disabling fsync and using copious quantities
of cache/buffer can almost eliminate actual disk access. My DB machine
will quickly blip the lights on the RAID array once a minute or so, but
that's about it. All of the actual work is happening from RAM. Of
course, with obscenely large data sets, that becomes difficult to achieve.
steve
