Re: requesting input on specs for a new Poky build server

[Darren Hart <dvhart@linux.intel.com>]

On 04/11/2011 05:03 PM, Tom Rini wrote:
> On 04/11/2011 02:50 PM, Joe Sauer wrote:
>> I have the pleasure of spec'ing out a new server for doing Poky builds
>> (we are at Green 3.3.1).  As a reference point, my desktop machine is a
>> quad-Xeon @ 2.5 GHz with 4GB of RAM and SATA disk.  I can do a full
>> "clean" build for our LabQuest (armv5te) in 2 hours.
>>
>> Here are some questions I would like to get feedback on regarding a
>> build server:
>>
>> 1.  Would I get better build time going with more procs (8?) or faster
>> procs (3+ GHz)?

I would go with more CPUs before I went with faster CPUs (at least from
2.5 to 3.3). Poky builds scale nicely to at least 16 physical cores (ie
4 quad-cores, hyperthreading is effective as well, but not so much as
physical cores), so until you get to that point, more is better in my
opinion.

>>
>> 2.  Are SATA drives OK, or should I go with RAID to get better R/W
>> performance?

A RAID 0 array of SATA drives is your best performing option (short of a
RAID 0 SSD array). You have to trade this extra performance for lower
reliability. RAID 0 has no redundancy, if one drive fails, all your data
is gone - so only keep recreatable data on the RAID array. I'd start
without RAID and test, see if you are maximizing your IO bandwidth.

>>
>> 3.  If I have to choose one or the other, should I go with faster procs
>> or faster disk I/O?

Provided you have a reasonably decent SATA controller on board, I'd opt
for _more_ procs.

> 
> If you're on somewhat of a budget, the general rule of thumb about going
> for last months fastest processor (as opposed to the one just released)
> is probably a wise bet.  And you probably want 8-12GB ram if you can fit it.
> 
> The only real and not always obvious trick is if you can afford an SSD
> (and afford to kill it and replace it every so often) doing your builds
> there is a real big win.

The failures are the scary part as you mentioned. I keep my git
repositories and downloads on an SSD and do my builds on a 2 disk RAID
array. I usually see either build dependencies or CPU as the bottleneck
before IO.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel