Re: [gentoo-amd64] Is there any difference with 4 core?

[Martin Nielsen <martin@skytech.dk>]

P.V.Anthony skrev:
> Hi,
>
> Need some more advice.
>
> Now the question is, is it better to go with 2 core or 4 core?
Hi,

Are you absolutely certain that your server can even max out cpu-wise? 
I've found in 99.99% of the cases it's usually other problems; not 
enough ram, io or simply wrongly configured services.

With the services you list I'd say if you simply have enough ram, the 
cpu really wont matter a thing. Since you'll seem to be doing some 
database applications I can only recommend an amd opteron. You dont even 
need a dc, but I guess the price difference these days are so small 
anyways :).

I'd prolly save the money on the Core2 CPU's and grab an amd opteron 
instead, dump software raid 1 and get something like 3ware SATA 
controller ( The 8000-model - 
http://www.3ware.com/products/serial_ata8000.asp ). Around here these 
things sell for roughly €175 or likewise but it's so much worth it. They 
come with in-kernel drivers as well as extra goodies in form of a 
service which can send you warnings/info/error so you'll always know the 
second a disk is fried. They come stock for debian, so I guess it's 
there for gentoo as well. They are even hotswappable if I remember 
correctly.

Sorry, sidetracked a bit.

I just don't think you'll ever max your cpu with the apps you listed. If 
you really have money to burn, smack in 4gb more ram instead - you'll 
take advantage of that way more than that extra cpu-power you'll never 
really use anyways (Im guessing tho - I dont know your actual usage 
patterns with the server)
>
> 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.
I dont have any factual data to back this up, but my coworker has stated 
on numerous occasions something like:
dual-core intel: 180% performance
dual-core amd: 190%
quad-core intel: 300%

Like I said, I dont have a clue whether that is true or not, so use that 
information with care :).

/Martin
>
> 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
>
> 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?
>
> 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.
>
> The other option is just to go with Pentium D with 2 core. That one is 
> a real saver.
>
> Please advice.
>
> P.V.Anthony
>

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