On Thu, 17 Feb 2005, Tom Lane wrote:
Evgeny Rodichev <[EMAIL PROTECTED]> writes:
Any claimed TPS rate exceeding your disk drive's rotation rate is a
red flag.
Write cache is enabled under Linux by default all the time I make deal
with it (since 1993).
You're playing with fire.
Yes. I'm lucky in this play :)
More seriously, we (with Oleg Bartunov) investigated many platforms/OS
for commercial, scientific and other applications during past 10-12
years. I suppose, virtually all excluding modern mainframes.
For reliability Linux + PostreSQL was found the best one (including the
environment with very frequent unexpected power-off, as at some astronomical
observatories at high mountains).
Hence, I'm lucky :)
fsync() really works fine as I switch off my notebook everyday 2-3 times,
and never had any data loss :)
Given that it's a notebook, it's possible that the hardware is smart
enough not to power down the disk until the disk is done writing
everything it's cached. Do you care to try some experiments with
pulling out the battery while Postgres is busy making updates?
Yes, you are exactly right. All modern HDDs (not entry level ones) has
a huge cache (at device, not at controller), and provide the safe hardware
flush of cache *after* power off (thanks capacitors). My HDD has 16MB cache,
and it is the reason for excellent performance.
Regards,
E.R.
_________________________________________________________________________
Evgeny Rodichev Sternberg Astronomical Institute
email: [EMAIL PROTECTED] Moscow State University
Phone: 007 (095) 939 2383
Fax: 007 (095) 932 8841 http://www.sai.msu.su/~er
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