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Re: Filesystem recommendations

Ron Johnson put forth on 5/3/2010 11:26 PM:
> On 04/26/2010 03:25 AM, Stan Hoeppner wrote:
> [snip]
>> If it took only 2 weeks for the bulk of this effort, I can't
>> imagine they had to modify a ton of XFS code.  IRIX was written in C
>> as is
>> Linux, so the changes in XFS were probably fairly minor.
> Windows is written in C, Linux is written in C.  Thus, it should be
> trivial to port Windows drivers to Linux?
> Obviously not.

They had it up and running in a couple of weeks.  A couple of weeks to me
would seem to say they didn't have to modify a ton of code.  Or, maybe
they're just really efficient programmers.  The truth probably lies
somewhere in between.

> Bottom line: just because two OSs are written in C doesn't mean that
> (even if they are both Unix work-alikes) they have the same "guts" (data
> structures, assumptions, etc).

I made no such statements about the "guts" being the same or similar.  I
simply stated that because both the Linux kernel and XFS were written in C
that the XFS code changes were probably fairly minor.  They didn't rewrite
it from the ground up.  I've never found any documentation that details the
changes and I don't have access to the original IRIX 6.5.x source code so I
can't do a diff on the XFS code.  I can only guess.  And knowing what I do,
I'm guessing I'm probably close to being on the money.

>> I'd venture to guess that the most significant Linux XFS changes were
>> those
>> for the 32bit X86 code base.  IRIX and thus XFS were born on 64bit
>> CPUs.
> I *know* that part of what you wrote is wrong, since SGI started using
> MIPS chips in 1986 and the MIPS 4000 is from 1991.

You are correct.  IRIX predates XFS by half a decade.  IRIX was developed
and released on the 32bit MIPS CPUs, the 2xxx and 3xxx series.

> http://en.wikipedia.org/wiki/IRIX#History
> http://en.wikipedia.org/wiki/SGI_IRIS_4D
> http://en.wikipedia.org/wiki/MIPS_architecture#CPU_family
> XFS is from 1994, so it did have it's genesis on a 64-bit platform.

And that's the only point I was making about the 32bit x86 work.  Even if
XFS wasn't originally developed on MIPS64 in 1992/93, the XFS code base in
2001 was fully 64 bit and had been for many many years.  Porting IRIX from
64bit MIPS to 64bit Itanium and other 64bit arches such as Alpha was far
less of an effort than "down" porting it to 32bit x86, which came some years
later, IIRC.  Such a project requires changing a ton of data structures from
8 bytes wide to 4 bytes wide.  The down port to 32bit x86 and the porting to
other architectures was, TTBOMK, required to get XFS into the mainline kernel.


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