Depends on array size, type of controller, amount of cache, type of
RAID arrays are not a good benefit for sequential access.
This really depends. For Pluto's application, using RAID 3 not only
us reliability, but also the ability to have one of the drives in a
"return late", but still maintain low latency by replacing the data
You are one of the few who still build RAID-3 arrays. Interesting...
Since we are a realtime system where being even a
little late is unacceptable, the use of RAID gives us a big advantage.
Almost all of our accesses are sequential.
I did not say that RAID arrays are not functionaly correct for Sequential
access. Just that perfromance in RAID arrays is les than optimal when
doing sequential access. In your case you ``do not have a choice'' but to
use a RAID (3, 5 or otherwise), as you cannot afford data disruption.
Simply, there is nothing free. If you want the reliability and
availability that a redundant array provides, there will be a performance
and capacity penalty.
BTW, the next generation DPT cards does all the parity computations in
hardware. Makes some difference in WRITE perfrormance and in degraded READ.
Shi...@Simon-Shapiro.ORG Voice: 503.799.2313
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