On Thu, 23 Aug 2001, Steve Wolfe wrote:
> > Don't use raid 5 if database performance is worth something to you.
> We use PostgreSQL on a hardware RAID controller, RAID 5. Our system has
> never had a stability problem in the 1+ year that it's been running, so I
> turned off fsync(). Between the 64 megs of cache on the controller and a
> gig of disk cache on the machine, the lights on the drives blink
> *occasionally*. I don't consider RAID 5 to be a problem at all, at least
> not in this situation. Our $12,000 machine will beat the $25,000 Alpha
> that a Compaq rep loaned to us. : )
Hmm yes, however our disk lights are lit a lot. A saw my co worker test
run a testconversion from guilders to euro in our logistics package which
kept the disk lit for over 40 minutes on the testbox.
Now this onvolves actually ploughing trough the complete 6GB+ of the
databases and changing fields and values. We are talking milions of
records that needed to be changed. Afterall this was just a desktop
machine but still this is going faster then the now in production machine.
The testmachine does not have any raid5 overhead and the production
machine does, which is probably the direct reason for the poor
performance. If you contact people about Progress/DB2/Oracleand similar
beasts you will get similar advice from their tech guru's.
We are rather diskbound with our server rather then processor.
The new machine will feature a dual 1Ghz PIII with at least 1GB of ram and
the raid will be a raid 10 totaling 6 disks with 2 raid0 sets which are
mirrored. The disks will be 73GB 10K RPM disks and each set of 3 will be
on it's own channel on the raid controller.
In case you want to order one, it's a Dell PE 2500 with rackmount kit an
6 73GB disks, UPS, and 3 year support. This brings the price in the
Netherlands to about 18.000 Euro (divide by 1.1 for US $).
Now this is fairly specific ofcourse but we are in the clothing retail
bussines wiht 200+ stores throughout the country and we have a lot of
unique items with specific prices for specific stores. etc. etc.
You get the idea, there will be about 50 people using this server
interactively and a lot of data is inserted automatically. The sales
information from all the cash registers, which then triggers the ordering
part which automatically creates list for what will need to be resent to
ther store, which triggers the finance part which is keeping the scores,
which triggers the inventory data so the stores can be checked on an anual
basis or whe know what is in it when it is stolen/burned
And you can't find that in the shops. It's a lot of hard work that has
been done over the years (7) and we like to please the users with a fast
way to bring them through their way.
But don't worry. I'll post benchmarks and some other data on my personal
websit when we get the machine.