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From: Paul Choi (paulchoiplaxo.com)
Date: Thu Apr 24 2008 - 12:18:16 CDT
I think what we need to know is more stuff about the database itself.
How big is it? I assume if you were able to serve it from a Mac Mini it
can't be all that big.
16GB should be big enough to contain all the data and serve it up quickly.
And while 4-disk RAID 5 isn't all that great, it's certainly better than
a single ATA disk in Mac Mini. If your database is huge, then 16GB is
barely enough to hold innodb buffer pool (if innodb) and maybe the
indexes. Then your RAID config will come into play (and maybe filesystem
type, tuning). Then whether it's a Dell PE1750 or a 6650 would not make
a huge difference since it's I/O bound.
Were you testing with something like production data or just some test
data? Have you modified my.cnf to reflect the new hardware config?
Like Baron Schwartz asked, does your test reflect real-life workload?
And yes, the 3.0Ghz Xeon processors you mentioned are 32-bit. You get
that error message if your processor doesn't have EM64T capability.
> We recently purchased a Dell PowerEdge 6650 thinking it would be a real fast
> Specs are:
> OS: Linux Debian 4.0/Etch
> RAID 5 on 4x U320 15k rpm drives
> (uses a perc-raid 3/DC hardware raid controller)
> 16GB of RAM
> 4 3.0 Ghz Xeon processors - I think they're dual core, in /proc/cpuinfo it
> shows up as 8 processors - maybe it's only HT
> I first made the mistake of using the default kernel, which provides SMP
> support but not large memory support.
> I have the output of a mysql sql-bench run from mysql on a Mac Mini to compare
> performance with.
> The server was only 0.35 (relative) the speed of the Mac mini - that means an
> 8 core 3.0 Ghz Xeon server with 16GB of RAM was only about 3x as fast as a as
> a single-core 1.25 Ghz G4 with 1GB of RAM (and a mini uses those
> little "laptop" hard drives, too).
> Needless to say my employer was shocked at the terrible performance and
> decided to sell the 6650 right away.
> But I can't help but wonder if there's not something terribly wrong with the
> settings - either the OS or mysql settings.
> I changed the kernel to the "-bigmem" kernel. It now sees all the RAM, but the
> sql-bench output on this try was _exactly_ the same: 0.35
> I copied the my-huge.cnf from the examples directory and changed the
> thread_concurrency setting to 8 (because it said to set it to No. of CPUs*2).
> I also set the tmpdir, basedir, datadir and language, which were set in the
> original my.cnf
> I ran sql-bench again and the performance was even worse this time: 0.36
> Someone suggested I try the -amd64 kernels which provide 64 bit but when I try
> to boot it I get various errors about "this CPU does not support long
> (something) please use a 32-bit OS" - the 64 bit install CD says the same
> message. So I assume these are not 64 bit CPUs.
> Any idea how I can configure this server to maximize performace?
> I think the multiple CPUs are a waste: I'm not looking for lots of
> concurrency, I want 1 query done really fast.
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