09-26-04 10:47 PM
First off, I couldn't say how many what kind of throughput and response
time you'd get with RAID 5 as compared with striping, but there are
even more factors that will come into play. These include raid group
size, IO size, randomness of reads, etc. If you bring your specific
requirements to an EMC rep, they should be able to enlist the help of a
performance expert who can show you a range of performance available
with the different configuration options.
Adding checkpoints doesn't seem like very much of a performance factor.
What you're really looking at is adding a pointer, and writing a new
block rather than replacing one. The real affect that it has is
consuming memory on the datamover, as those pointers are kept in memory
for quick access to them. Memory, though, isn't typically in
contention on the datamover. Again, more details can probably be
gleaned from an EMC performance expert. They have graphs on all this
stuff...
As to a fsck'ing: uxfs is a journaling filesystem now, and almost all
filesystem corruption-- should it occur-- shoule be fixable without a
fsck. Moreover, the Clariion within the NS700 has enough battery power
to destage writes to disk from cache before the system powers off,
thereby preventing any corruption. Also, though I've never needed to
fsck, I really couldn't imagine it taking several *days* for any size
of filesystem.
HTH
Aaron
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