RE: 4 Disk Raid5 Performance over 3 Disk Raid5 Performance

I agree %100 with you, but I sure hate doing PTFs and OS Upgrades compared 
to the same CPW/Memory with a larger raid set.


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Kirk Goins CCNA
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RE: 4 Disk Raid5 Performance over 3 Disk Raid5 Performance







midrange-l-request@xxxxxxxxxxxx wrote:

  9. 4 Disk Raid5 Performance over 3 Disk Raid5 Performance
     (kirkg)

I know from real life that a system with a 3 drive raid5 set performs 
almost as bad as a 2 drive mirrored  set. Now I need some official doc 
that says a 4 drive raid5 set out performs a 3 drive raid5  set.  Anyone 
seen something like this?

Unfortunately, no, I haven't seen actual docs. But for the sake of 
completeness on the concept, I want to add a "lunatic fringe" comment... 
NOT to be confused with any form of "recommendation"!

While a 3-drive RAID5 set may perform far worse than 4 or more drives in a 
set, it _might_ not perform badly enough to ignore as a possibility. We 
moved a couple systems from some old hardware to a couple of the 
partitions on a new box, both partitions with 3-drive RAID5 sets, and both 
are so much blazingly faster than the old that we fail to see what the 
complaints are about.

MAJOR caveat -- our processing is ***NOT*** typical and definitely not 
database bound. But when we run a *FULL build of a significant product, we 
still get a big chunk of AuxIO.

The only point is that _sometimes_ for unusual circumstances, a 3-drive 
set can work well. The sum of performance boosts from various components 
after upgrading to new hardware can be impressive.

Tom Liotta