[gentoo-amd64] Re: MAKEOPTS values for Athlon 64 X2

[Duncan <1i5t5.duncan@cox.net>]

Thomas Rösner <Thomas.Roesner@digital-trauma.de> posted
45AC0F0A.5050408@digital-trauma.de, excerpted below, on  Tue, 16 Jan 2007
00:32:26 +0100:

> Duncan wrote:
>> As for disk access, the average guy with a single hard drive will
>> certainly find that the bottleneck in an unlimited jobs scenario such as
>> the above.  I'm running a four disk SATA based RAID array, RAID-6 (so
>> two-way-striped, with two-way recovery as well) on my main system,
> 
> Uhm, if you'd use RAID-1-1, you wouldn't have to calculate those
> checksums...

True, but computing checksums is relatively trivial compared to the I/O
overhead, and reading (which doesn't need checksums unless the
RAID array is operating in degraded mode) would be half-speed relative to a
4-disk RAID-6 (so two-way data striped). Given the trivial checksumming,
Writing would be comparable to a three-disk RAID-1, and is slower than a
two-disk RAID-1, as for every data stripe there's two parity stripes to
update, but there's not a lot of data actually written anyway during
emerges, since all the work is done on tmpfs and only the final write is
to the disk.  When compiling the kernel, I'm working directly on disk but
that mount is a four-way striped RAID-0, so I get its speed and no
checksumming overhead there.  (/boot is RAID-1 so GRUB can read it, so
when the kernel is actually installed, it's written to 4-way RAID-1, but
that's only one writing the completed kernel, so no big deal there.)

If I was running less than four disks, the choice would be a bit tougher,
between a 3-disk RAID-5 with two-way striped read speed but
two-way-mirrored (plus checksumming) write speed, while losing the
ability to recover from a two-drive failure, a 3-disk RAID-1, keeping the
two-drive recovery but at a severe cost in speed, or a 2-disk
RAID-1/mirrored. In that instance I expect the 2-disk RAID-1/mirrored
would win as it would be too difficult to justify either of the 3-disk
options.

> Btw, may I come to your place when UT2007 is out? ;-)

As a gamer, you'd probably not appreciate my choice of video card -- an
older but freedomware driver Radeon 9250.  I won't do
proprietaryware/slaveryware.

Luckily I'm not much of a gamer, but the rest of the hardware specs are
complimented by dual 400x300 mm (21" diag) monitors, normally running @
1600x1200 stacked for 1600x2400. I used to run 2048x1536 stacked for
2048x3072, but while it worked, text was blurry as that was below the
monitors' native pixel pitch (set for 1600x1200), and the 85 Hz refresh
doesn't hurt (I was limited to 60 Hz with the higher resolution,
acceptable with the light text on dark backgrounds I prefer, but not
ideal, or even tolerable with dark text on light backgrouns) either, so I
finally caved in and downgraded my resolution.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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