building a RAID system
hahn at physics.mcmaster.ca
Wed Oct 8 19:39:41 EDT 2003
> I would like to know some advice about what kind of technology apply
> into a RAID file server ( through NFS ) . We started choosing hardware
> RAID to reduce cpu usage.
that's unfortunate, since the main way HW raid saves CPU usage is
by running slower ;)
seriously, CPU usage is NOT a problem with any normal HW raid,
simply because a modern CPU and memory system is *so* much better
suited to performing raid5 opterations than the piddly little
controller in a HW raid card. the master/fileserver for my
cluster is fairly mundane (dual-xeon, i7500, dual PC1600), and
it can *easily* saturate its gigabit connection. after all, ram
runs at around 2 GB/s sustained, and the CPU can checksum at 3 GB/s!
concern for PCI congestion is a much more serious issue.
finally, why do you care at all? are you fileserving through
a fast (>300 MB/s) network like quadrics/myrinet/IB? most people
limp along at a measly gigabit, which even a two-ide-disk raid0
> The server has a dozen of client workstations connected through a
> switched 100Mbit LAN , all of these equipped with it's own OS and
jeez, since your limited to 10 MB/s, you could do raid5 on a 486
and still saturate the net. seriously, CPU consumption is NOT an issue
at 10 MB/s.
> machines tough, server only takes care of file sharing.
so excess cycles on the fileserver will be wasted unless used.
> Considering that not all the workstantions would be working full time
> and with cost in mind ¿ it's worth an ATA RAID solution ?
you should buy a single promise sata150 tx4 and four big sata disks
(7200 RPM 3-year models, please).
regards, mark hahn.
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