Hi, On Wed, Apr 23, 2008 at 11:07 PM, JW <[EMAIL PROTECTED]> wrote: > Hello, > > We recently purchased a Dell PowerEdge 6650 thinking it would be a real fast > server. > > 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.
They almost certainly are. Look at the contents of /proc/cpuinfo. You are probably using a 32-bit OS. You can't use a lot of memory efficiently unless you install a 64-bit OS, regardless of whether it has "big memory support". But that's an x86_64 OS, not an AMD64 OS. These are not the same architecture. > 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. You will be bound by CPU performance on any given single query, yes. But properly tuned, you may get a lot more performance out of this machine. Have you tuned MySQL (key_buffer_size and/or innodb_buffer_pool_size) to use the added memory, for starters? How much data do you even have? If your data all fits in the mac mini's memory and it has a comparable CPU and bus, I wouldn't be surprised to see it keeping up with the Dell fairly well on this benchmark. More to the point: does the benchmark reflect your real-life workload? Baron -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
