P.V.Anthony, mused, then expounded:
> Hi,
>
> Need some more advice.
>
> Now the question is, is it better to go with 2 core or 4 core?
>
> The reason for this question is, that I heard there is a diminishing
> return with more cores. Not sure if this is true with kernel 2.6.21 and
> running at 64bit.
>
As far as the kernel is concerned, there are no issues. I've run on
a 1024 shared memory ccNUMA system and regularly started up and killed
1024 jobs withiout problems.
> The server needed to built is for the following apps.
>
> Hardware.
> 1. Tyan Tank GT20 (B5191)
> 2. 2 x Sata drives
> 3. Software raid 1
> 4. 4Gb ram ecc
> 5. Intel Core2Duo E6420 or Intel Core2Quad E6600
>
The Intel platform does not scale all that well. Plus it has
limited I/O abilities. You will find a lot of issues with
high i/o bandwidth simultanous applications.
That said, it compiles like a screaming banshee. We currenly
run ongoing testing on a small cluster of something like the
above - 16 blades with quad core cpus (128P), running diskless
over dual Infiniband links to lead and login nodes, dual core
1U boxes with hardware raid.
> Apps.
> 1. Gentoo linux 64bit
> 2. Apache 2
> 3. MySql
> 4. Postgres
> 5. Qmail
> 6. Pure-ftpd
> 7. Mod_perl
> 8. php
> 9. ruby
>
> Will all the instances of the apps be shared among the cores?
>
Good question. Without something like cpu sets, the sharing won't
be equal amoung all cpus.
> Please share the comments.
>
> I would really like to save some money. If the 2 core can do the job
> there is quite a bit of savings buying just the 2 core.
>
Regardless of Intel platform, FSB saturaton will ocur due to the
ancient bus. Additionally, unless you run 4-dimms, max memory
bandwidth will not be achieved. Typically for the Intel 5000
chipset the motherboards have 8 DIMM slots. I see the one in the
tank only has 6. Intel's northbridge came split the data up
over 4 dimms to maximize bandwidth. It's important to performance.
Additionally, there are other power savings issues to note -
Woodcrest (dual core) does not support EIST (enhanced speed step)
Clovertwon (quad core) does support EIST
Memory should be run in performance mode. Allowing memory to
be set into dynamic power mode (power savings) will decrease
the max available bandwidth.
Of the power saving software, powernowd allows better tuning and
response to load changes. Much better than cpufreqd.
> The other option is just to go with Pentium D with 2 core. That one is a
> real saver.
>
And it's a crappy cpu. Don't waste you're money. Any AMD cpu running
at half it's speed will eat it alive.
Bob
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