[resolved, ?naively] Re: geom vs ich through ar device - benchmarks?

[Oliver Fromme]

Scott Long wrote:
 > Howard Goldstein wrote:
 > > Naive test:  dd if=/dev/zero of=/fsundertest/tstfile bs=1m count=1000
 > > *not including buffered stuff unwritten, the test simply reported dd's
 > > idea of the transfer time*, and then the other way where it doesn't matter
 > > 
 > >  In firmware's RAID1                       Using the awesome gmirror
 > > write 1gb: 13.275                             13.7
 > > rd         12.9                               13.8
 > > 
 > > Of course after this I used gmirror...
 > 
 > Just so we're clear, the ICH5 doesn't have any firmware and doesn't
 > actually do any RAID operations.  What is has is hook into the system
 > BIOS during boot.  That hook allows the BIOS to do RAID-like operations
 > during boot, until the OS takes over control of the devices.  After
 > that, it's up to the OS to do all the RAID work.  The 'ar' driver is
 > still software RAID, just like gmirror.  What you've effectively done
 > merely compare the performance of one software RAID stack to another.
 > That's certainly an interesting comparison, but maybe not exactly what
 > you had in mind.

As an additional note:  _If_ the ICH RAID was in hardware
(which it isn't, as Scott pointed out), it might be
preferable to use it instead of gmirror, even if it's 5%
slower, but because it would save a lot of cpu.

Of course, since both are in software and probably consume
similar amounts of cpu, it's better to use gmirror because
it's a little faster.

Best regards
   Oliver

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