Someone correct me if I'm wrong. The actual throughput on the FC
controller on the XServe RAID is somewhere around 80MB/s?
correct
The throughput on the FC cabling is theoretically 200MB/s? What
about a switch, say a QLogic SANbox 5200? What is the realistic
throughput for that (or a similar switch, or any switch)?
depending on brand, but usually at least several times 200 MB/s
(typically more than 4 GB/s backbone in them), so unless you will use
many Xserve Raids systems and many concurrent clients (lets say more
than 10 of each) the switch is not the bottleneck
How about the throughput through the Apple FC card?
200 MB/s per port, so 400 MB/s in total
PCI, PCI-X, PCIe versions of their card? Are these throughput
numbers even important?
Yes, PCI is too low, PCI-X or PCI Epress needed.
Examples to explain this:
small test Xsan with 2 Xserve RAID's (4 LUN's of 6 disk Raid5) one
small third-party Metadata LUN (HP MSA1000)
Emulex 355 switch (=switching hub, backbone of 4 GB/s afaik)
1 MCC Xserve G5, 2 clients G5, all Apple PCI-X FC cards, both ports
connected to FC switch, read/write test with Xsan Tuner
client 1: G5 with PCI slots : max 230 MB/s read/write (bottleneck is
64 bit PCI slot, 266 MB/s)
Client 2: G5 with PCI-X slots : max 320 MB/s read/write (bottleneck
are 4 LUNs x 80 MB/s)
If you disconnect one FC cable, for both clients the max is about 180
MB/s (bottleneck is single FC connection of 200 MB/s)
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