[yocto] Server specs for a continuous integration system

[Elvis Dowson]

Hi,

On Sep 3, 2013, at 3:29 AM, Christian Gagneraud <chgans at gna.org> wrote:

>> Isn't RAID-5 going to be slower, especially if it's software? RAID 1
>> is probably better as you'll potentially double the write speed to disk.
>> I use a couple of Vertex SSDs in RAID 1 giving a theoretical write speed
>> near to 1GBs. Write endurance is possibly a concern, but I've not had
>> any issues using them on a local build machine. I would probably look at
>> some higher end models if I was going to run a lot of builds. A lot less
>> noise than hard drives ;-)
> 
> Thanks for the info, i will have a look at RAID-1, as you can see, I know absolutely nothing about RAID! ;)
> 
> Does SSD really help with disk throughput? Then what's the point of using ramdisk for TMPDIR/WORKDIR? If you "fully" work in RAM, the disk bottleneck shouldn't be such a problem anymore (basically, on disk, you should only have your yocto source tree and your download directory?).

I use a Gigabyte Z77X-UP5TH motherboard 

http://www.gigabyte.us/press-center/news-page.aspx?nid=1166

which has support for RAID in BIOS, at boot up, and Thunderbolt connected to an Apple 27" Thunderbolt display. I've got two SSDs in a RAID1 configuration (striped).

If you can wait for some more time, they'll be releasing a version of the motherboard for the new haswell chips as well, but it's not probably going to increase performance. 

I use a 3770K i7 quad-core processor, 16GB RAM, with a liquid cooled solution running at 3.8GHz. I've overclocked the CPU to 4.5GHz, but I end up shaving only 2 minutes off build times, so I just run it at 3.8GHz.

A core-image-minimal build takes around 22 minutes for me, for a Xilinx ZC702 machine configuration (Dual ARM Cortex A9 processor + FPGA).

Here are the modifications that I've done to my system, to tweak SSD performance, for Ubuntu-12.10, for a RAID1 array.

SSD performance tweaks (for non RAID0 arrays)

Step 01.01: Modify /etc/fstab.

$ sudo gedit /etc/fstab

Increase the life of the SSD by reducing how much the OS writes to the disk. If you don't need to knowwhen each file or directory was last accessed, add the following two options to the /etc/fstab file:

noatime, nodiratime

To enable TRIM support to help manage disk performance over the long term, add the following option to the /etc/fstab file:

discard

The /etc/fstab file should look like this:

# / was on /dev/sda1 during installation
UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx /               ext4    discard,noatime,nodiratime,errors=remount-ro 0       1

Move /tmp to RAM

# Move /tmp to RAM
none            /tmp            tmpfs       defaults,noatime,nodiratime,noexec,nodev,nosuid 0      0

See: Guide software RAID/LVM TRIM support on Linux for more details.

Step 01.02: Move the browser's cache to a tmpfs in RAM

Launch firefox and type the following in the location bar:

about:config

Right click and enter a new preference configution by selecting the New->String option.

Preference name: 	browser.cache.disk.parent_directory
string value:		/tmp/firefox-cache

See: Running Ubuntu and other Linux flavors on an SSD « Brizoma.


Best regards,

Elvis Dowson
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