scott.marlowe wrote:
>I can get aggregate reads of about 48 Megs a second on a pair of 10k 18
>gig UW scsi drives in RAID1 config. I'm not saying there's no room for
>improvement, but for what I use it for, it gives very good performance.
>
>
>
Scott,
as most people talking about performance you mean throughput, but this
is not the most important parameter for databases. Reading the comments
of other users with software and IDE RAID, it seems to me that indeed
these solutions are only good at this discipline.
Another suggestion:
You're right, a hardware RAID controller is nothing but a stripped down
system that does noting more than a software RAID would do either. But
this tends to be the discussion that Intels plays for years now. There
were times when Intel said "don't need an intelligent graphics
controller, just use a fast processor". Well, development went another
direction, and it's good this way. Same with specialized controllers.
They will take burden from the central processing unit, which can
concentrate on the complicated things, not just getting some block from
disk. Look at most Intel based servers. Often, CPU Speed is less than
workstations CPUs, RAM technology one step behind. But they have
sophisticated infrastructure for coprocessing. This is the way to speed
things up, not pumping up the CPU.
If you got two of three HDs bad in a RAID5 array, you're lost. That's
the case for all RAID5 solutions, because the redundancy is just one
disk. Better solutions will allow for spare disks that jump in as soon
as one fails, hopefully it rebuilds before the next fails.
Regards,
Andreas
