On 12/30/2007 12:06 AM, Linda Walsh wrote: > I needed to get a new hard disk for one of my systems and thought that > it was about time to start going with SATA. > > I picked up a Promise 4-Port Sata300-TX4 to go with a 750G > Seagate SATA -- I'd had good luck with a Promise ATA100 (P)ATA > and lower capacity Seagates and thought it would be a good combo. > > Unfortunately, the *buffered* read performance is *horrible*! > > I timed the new disk against a 400GB PATA and old 80MB/s SCSI-based > 18.3G hard disk. While the raw speed numbers are faster as expected, > the linux-buffered read numbers are not good. > > > sda=18.3G on 80MB/s SCSI > sdb=the new 750GB on a 3Gb SATA w/NCQ. > hdf=400GB PATA on an ATA100 Promise card > > I used "dd" for my tests, reading 2GB on a quiescent machine > that has 1GB of main memory. Output was to dev null. Input > was from the device (not a partition or file), (/dev/sda, /dev/sdb > and /dev/hdf). BS=1M, Count=2k. For the direct tests, I used > the "iflag=direct" param. No RAID or "volumes" are involved. > > In each case, I took best run time out of 3 runs. > > Direct read speeds (and cpu usage): > dev speed cpu/real % > sda 60MB/s 0.51/35.84 1.44 > sdb 80MB/s 0.50/26.72 1.87 > hdf 69.4MB/s 0.51/30.92 1.68 > > > Buffered reads show the "bad news": > dev speed cpu/real % > sda 59.9MB/s 20.80/35.86 58.03 > sdb 18.7MB/s 16.07/114.73 14.01 <-SATA extra badness > hdf 69.8MB/s 17.37/30.76 56.48 > > I assume this isn't expected behavior. >
Try the PATA driver for the parallel ATA drive to see if it has the same behavior. Reboot before each test (or use drop_caches.) hdparm should mostly work for reading drive settings but not for writing them... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
