Problem turned out with advanced power management settings with my drive. $ hdparm -B 128 /dev/sdb
I get consistent 60 MB/sec speeds. Any number below 128 ends up as APM_level=1, and I get 30MB/sec if I wait few 10's of seconds between running hdparm. Its surprising because I have set standby time on the drive to 30 minutes. As you suspected also, cycle time was very high net6501 ~ # smartctl --all /dev/sdb|grep -i cycle 12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 200 225 Load_Cycle_Count 0x0032 002 002 000 Old_age Always - 999999 FYI, my drive is: Model Family: SAMSUNG SpinPoint M6 Device Model: SAMSUNG HM500LI Thanks for the pointers Nikhil PS: I did see your OCZ numbers, which is SSD and your numbers seem to match what I get from my mSATA ssd (sorry, I realized that I called it minipcie ssd in my first mail). On Mon, Aug 13, 2012 at 10:59 PM, Chris Wilson <[email protected]> wrote: > Hi Nikhil, > > > On Mon, 13 Aug 2012, Nikhil Sethi (निखिल सेठी) wrote: > >> Using dd to seek to random places in disk and reading I think I am >> getting ~60MB/sec which is more respectable. It varies a lot more if I >> only read ~200MB which is what hdparm seems to do. >> >> net6501 ~ # time dd if=/dev/sdb bs=$((1024*1024)) >> seek=$((54565*1024*1024)) count=1024 of=/dev/null >> 1024+0 records in >> 1024+0 records out >> 1073741824 bytes (1.1 GB) copied, 17.9964 s, 59.7 MB/s > > > Perhaps the disk goes into power saving mode (spins down) quite quickly, and > therefore during the first test it has to wake up, but in subsequent tests > it's still spinning? > > You might want to watch out for fast-rising Load Cycle Counts if that's > happening. > > >>> Yes. It does seem quite low, so I think I might have mis-configured >>> something. Would be nice to hear someone getting higher speeds. > > > Did you get the numbers I posted? > > Using a different disk, the OCZ Solid3 SSD: > > Timing cached reads: 852 MB in 2.00 seconds = 425.98 MB/sec > Timing buffered disk reads: 342 MB in 3.02 seconds = 113.24 MB/sec > > Cheers, Chris. > > -- > Aptivate | http://www.aptivate.org | Phone: +44 1223 967 838 > Future Business, Cam City FC, Milton Rd, Cambridge, CB4 1UY, UK > > Aptivate is a not-for-profit company registered in England and Wales > with company number 04980791. _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
