On Sep 15, 2009, at 7:32 PM, Drew wrote:
Thanks for the input. Sounds from your testing like PMs can deliver the sorts of speeds that are adequate for our needs.
Given a decent SATA port (like the Sil3132) and a motherboard that allows this port to run at full speed (one that can up the max PCI-e payload limit above 128 bytes), then yes. I'm sure other port types out there would work without the PCI-e requirement, but I don't have any of those for testing.
Have you done any testing as far as md RAID using member disks from each PM?
I've only got one PM at the moment.
Given we're expecting a mix of online and archival data going onto this enclosure I was thinking about making up RAID arrays composed of disks from each PM for online use and arrays composed of disks from a PM for archival use.
Well, I might suggest something like doing 3 disks from each PM as part of the archive and one disk from each PM as the online storage. In a scenario like that, the archive system will run slower than the online system, but as long as the online system and archive system aren't currently fighting for bandwidth, the online system will get full speed (assuming the online disks can't go faster than 120MB/s each). And that's without having to find a motherboard that lets you set the PCI-e payload size. Another option is the online disks can be internal disks, with at most one disk per PM. That array would be blindingly fast. You can then make the archive array(s) use the remaining PM connected drives.
I'm sorry if I keep throwing questions out without doing my own testing. As I alluded to earlier I don't have an R&D budget for testing so I have to be reasonably sure of my system before I can get authorization to purchase kit.
-- Doug Ledford <dledford@xxxxxxxxxx> GPG KeyID: CFBFF194 http://people.redhat.com/dledford InfiniBand Specific RPMS http://people.redhat.com/dledford/Infiniband
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