Karim writes: > It is quite obvious that something is awfully slow on SAS drives, > whatever it is and regardless of OS comparison. We swapped the SAS > drives for SATA and we're seeing much higher speeds. Basically on par > with what we were expecting (roughly 300 to 400 times faster then what > we see with SAS...).
Major clue there! According to wikipedia: "Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing" [1] Note that the driver says "Command Queueing enabled" without specifying which. If the driver is trying to use SATA's NCQ but the drive only speaks SCSI's TCQ, that could explain it. Or if the TCQ isn't working for some other reason. See if there are any error messages in dmesg or /var/log. If not, perhaps the driver has extra debugging you could turn on. Get TCQ working and make sure your partitions are aligned on 4 KiB boundaries (in case the drive actually has 4 KiB sectors), and you should get the expected performance. [1] http://en.wikipedia.org/wiki/Serial_attached_SCSI _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
