I've not gotten everything working just fine with the MegaRAID card (AMI QLA12160 = Dell PowerEdge RAID Controller 3/DC). I've been doing a bit of performance testing, and with HD Tune (I realize this doesn't necessarily give good absolute numbers, but at least it should give a good measure for drives in the same system).
My main internal RAID on the workstation is a RAID5 of four 143 GB Seagate Savvio 10K.2 drives, which gives an average read transfer rate of 203 MB/s.
For comparison, I also benchmarked my little 120 GB Lacie portable hard drive (5400 rpm, 2.5" drive). Over firewire, it was about 29 MB/s; over USB, about 28 MB/s.
I also have a Thecus N5200 Pro, which is an iSCSI box with five SATA Seagate Barracuda ES.2 drives in a RAID five, which had an average transfer rate of about 36.5 MB/s.
Finally, the two RAIDs setup within the Open-E DSS Lite box, which is a Dell Precision Workstation 690, 3 GB of RAM, with the aforementioned MegaRAID two-channel RAID card with 64 MB of RAM. The first setup is a RAID0 of two 10,000 RPM 300 GB Maxtor Atlas 10K.V U320 SCSI drives. This gave a transfer rate of 29.5 MB/s. The second setup has four 73 GB Seagate Cheetah 15K.3 drives in a RAID 5. It's transfer rate was about 26.2 MB/s. In all cases, reading and writing cache were both enabled.
What I don't understand is why the RAID setups in the Open-E setup are so slow. Internally, they are good for hundreds of megabytes per second. All of the machines have GbE, and 30-40 MB/s is nowhere near the maximum bandwidth, even for a single adapter.
But the performance I"m getting from dedicated SCSI hardware is poorer than that from a plug-in USB drive. What am I doing wrong? What can I do to fix this?
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