Mailinglist Archive: opensuse-factory (439 mails)

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Re: [opensuse-factory] Re: Re: Adding SSDs?
On Tue, 11 Mar 2014 07:04, Jason <relentropy@...> wrote:
On Tuesday, March 11, 2014 06:37:52 Yamaban wrote:

Please be aware, that most of the preformance boost will only start AFTER
the kernel it self has been loaded.

The kernel (+ initrd) are loaded by the BIOS / UEFI and there the boost a
SSD gives isn't that great difference (< 100MB)

Seriously? Where are you pulling this from, I'd like to see.

Q: Fit on history and some basic math?

Look up the origanl BIOS Boot-Loader routines
(Hints: DOS, asm, int13h)

Now look up what a recent BIOS does.
Look up UEFI Boot-Loader routines.

See the differences?

Look into your /boot dir, add the size of your kernel and your initrd.

Look at the specs of your disk, continous transfer-rate, take about 60%
of that (some UEFI implemtations are a little better and reach 80%).

Divide the sum of kernel and initrd by the reduced transferrate.

Now you have the pure time it takes to load the kernel and the initrd
into memory.

If you take a older Laptop HDD (27 MB/s) and a newer SSD (150MB/s)
the difference looks big, but the size of the kernel+initrd
is not that big that the difference will make more than one (1)
second of boot time.

After the kernel is loaded, the BIOS / UEFI will give control to
the kernel, which initializes the HW with its drivers.
Here comes the kernels own IO routines to play.

Now the kernel loads the rest of the OS with its own
(optimized) routines.

And here most of the Disk I/O of the Boot / Restore
process happens.

Now the higher transfer-rates and near marginal seek times
of a SSD comes fully into play.

My first PC was a i386 / 25Mhz / 512kB-RAM /
40MB-ST506-HDD / VGA (640x480/256colors)
in spring 1990.

After some GW-Basic I learned Assembler.
Some where I still have a complete BIOS
in ASM laying around.

Prove Yourself. Seek Your own answers.

- Yamaban.

PS: Startpoint for the uninformed:
http://en.wikipedia.org/wiki/BIOS
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