Re: Build time data

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

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On 04/12/2012 10:51 PM, Martin Jansa wrote:

> And my system is very slow compared to yours, I've found my
> measurement of core-image-minimal-with-mtdutils around 95 mins 
> http://patchwork.openembedded.org/patch/17039/ but this was with
> Phenom II X4 965, 4GB RAM, RAID0 (3 SATA2 disks) for WORKDIR, RAID5
> (the same 3 SATA2 disks) BUILDDIR (raid as mdraid), now I have
> Bulldozer AMD FX(tm)-8120, 16GB RAM, still the same RAID0 but 
> different motherboard..

Why RAID5 for BUILDDIR? The write overhead of RAID5 is very high. The
savings RAID5 alots you is more significant with more disks, but with
3 disks it's only 1 disk better than RAID10, with a lot more overhead.

I spent some time outlining all this a while back:
http://www.dvhart.com/2011/03/qnap_ts419p_configuration_raid_levels_and_throughput/

Here's the relevant bit:

"RAID 5 distributes parity across all the drives in the array, this
parity calculation is both compute intensive and IO intensive. Every
write requires the parity calculation, and data must be written to
every drive."



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