On Fri, 2006-03-24 at 01:31, vanja@pobox.com wrote:
So, that 200GB Maxtor has no problems writing (300MB file gets written in few seconds, when it's read from another 80GB SATA disk), but when I read something from that disk - I get 2MB/sec. I have no trouble reading from 80GB SATA disk, so I guess it will be cable/hardware related.
Writing is always buffered and unless you do some kind of fsync you don't know when it is committed back to disk. Your timing will stop when it goes to the RAM buffer. Reading is buffered too, but the first read obviously has to wait for the disk.
I have no idea why hdparm reports 50MB/sec rates on 200GB disk, but I'll just assume that hdparm doesn't use "real life" way of testing speed :)
Change your tests to use large enough samples that you can't buffer a significant part in RAM. Anyway the usual problem with IDE/SATA vs. SCSI is not sustained transfer in a single operation, it is that scsi will accept and buffer multiple commands while most ide/sata drives (the WD raptor being an exception) can only have a single command waiting for completion - and with IDE that is per controller.