Thread: Best hardware

Hi there,

And sorry for bringing this up again, but I couldn't find any recent
discussion on the best hardware, and I know it actually depends on what you
are doing...

So this is what I had in mind:

Our database is going to consist of about 100 tables or so of which only a
hand full will be really big, say in the 100 of million rows, fully indexed
and we are going to add a lot of entries (n* 100 000, n<100) on a daily
bases (24/5). So from my experience with MySql I know that it is somewhat
hard on the I/O, and that the speed of the head of the HD is actually
limitiing. Also, I only experimented with RAID5, and heard that RAID10 will
be good for reading but not writing.

So I wanted to go whith RAIDKing. They have a 16 bay Raid box that they fill
with Raptors (10krpm,73 GB, SATA), connected via FC. Now I am not sure what
server would be good or if I should go with redundant servers. Are Quad CPUs
any good? I heard that the IBM quad system is supposed to be 40% faster than
HP or Dell???. And how much RAM should go for: are 8GB enough? Oh, of course
I wanted to run it under RedHat...

I would appreciate any sugestions and comments or if you are too bored with
this topic, just send me a link where I can read up on this....

Thanks a lot for your kind replies.

Bernd


Bernd Jagla, PhD
Associate Research Scientist
Columbia University

Quoting Bernd Jagla <baj2107@columbia.edu>:

> ... the speed of the head of the HD is actually
> limitiing. Also, I only experimented with RAID5, and heard that
> RAID10 will be good for reading but not writing.

Au contraire. RAID5 is worse than RAID10 for writing, because it has the
extra implicit read (parity stripe) for every write. I've switched all
my perftest boxes over from RAID5 to RAID10, and the smallest
performance increase was x1.6 . This is in an update-intensive system;
the WAL log's disk write rate was the controlling factor.

> Are Quad CPUs any good? I heard that the IBM quad system is supposed
to be 40%
> faster than HP or Dell???.
Check out the other threads for negative experiences with Xeon 2x2 and
perhaps quad CPU's. Me, I'm looking forward to my first Opteron box
arriving next week.

> And how much RAM should go for: are 8GB enough? Oh, of course I wanted
to run it under RedHat...

First off, you need enough RAM to hold all your connections. Run your
app, watch the RSS column of "ps". For my own simpler apps (that pump
data into the db) I allow 20MB/connection.

Next, if you are heavy on inserts, your tables will never fit in RAM,
and you really just need enough to hold the top levels of the indexes.
Look at the disk space used in your $PGDATA/base/<dboid>/<tableoid>
files, and you can work out whether holding ALL your indexes in memory
is feasible.

If you are heavy on updates, the above holds, but ymmv depending on
locality of reference, you have to run your own tests.

If you have concurrent big queries, all bets are off --- ask not how
much RAM you need, but how much you can afford :-)

Hello Bernd Jagla,

Are you the Bernd from Berlin? I am looking for you and found your name on the internet. Would you please contact me?

Mirjam Tilstra

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Re: Best hardware