On 31/05/07, Mark Lord <liml@xxxxxx> wrote:
Daniel J Blueman wrote:
> Whoops, yes. Here is the expected data:
[snip]
Thanks. I'll use that data to update/validate future versions of hdparm.
At UDMA66, it *should* be capable of the 40MByte/sec realm of readback perf,
assuming the card itself is really that fast.
hdparm in the other identify mode does list the UDMA3/4 modes twice
[1], which looks odd.
I don't know too much about the specifics, though, but perhaps the
card is only capable of full speed in PIO6, which requires special cabling
and is currently unsupported in libata (?).
Seems less likely, as the Extreme IV reader (and another) supports
UDMA mode 4; in PIO mode 6, they apparently top out at 17MB/s [2],
which seems reasonable.
Another factor, is that hdparm performs discrete, non-overlapping,
reads of 1MByte chunks for its timing test. Some drives cannot achieve
full performance with such (relatively) large gaps between IO's.
100MB transfers still achieve 32MB/s:
# dd if=/dev/sdb of=/dev/null bs=100000k count=10
10+0 records in
10+0 records out
1024000000 bytes (1.0 GB) copied, 31.9328 seconds, 32.1 MB/s
Also, just for fun, you could try "hdparm --direct -t /dev/sdb"
# hdparm --direct -t /dev/sdb
/dev/sdb:
Timing O_DIRECT disk reads: 96 MB in 3.05 seconds = 31.47 MB/sec
It is conceivable that the controller in the two particular readers
which get 40MB/s are doing some kind of prefetching, but seems seems
like an extreme gain.
I'll check things out with the IDE PIIX code also. Thanks for your help!
Daniel
Cheers
--- [1]
# hdparm -i /dev/sdb
/dev/sdb:
Model=SanDisk SDCFX-4096 , FwRev=HDX 4.04,
SerialNo= 116802D2807J3335
Config={ HardSect NotMFM Removeable DTR>10Mbs nonMagnetic }
RawCHS=7964/16/63, TrkSize=0, SectSize=576, ECCbytes=4
BuffType=DualPort, BuffSize=1kB, MaxMultSect=4, MultSect=?0?
CurCHS=7964/16/63, CurSects=8027712, LBA=yes, LBAsects=8027712
IORDY=no, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 *udma4 udma3 *udma4
AdvancedPM=no WriteCache=disabled
Drive conforms to: Unspecified: ATA/ATAPI-4
* signifies the current active mode
--- [2]
http://www.robgalbraith.com/bins/content_page.asp?cid=7-7896-8475
--
Daniel J Blueman
-
To unsubscribe from this list: send the line "unsubscribe linux-ide" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
