Messages in this thread | | | Date | Mon, 19 Mar 2001 12:17:38 -0800 | From | Tim Moore <> | Subject | Re: UDMA 100 / PIIX4 question |
| |
Jeremy Jackson wrote: > > Tim Moore wrote: > > 15MB/s for hdparm is about right. > > Yes, since hdparm -t measures *SUSTAINED* transfers... the actual "head rate" of data reads from > disk surface. Only if you read *only* data that is alread in harddrive's cache will you get a speed > close to the UDMA mode of the drive/controller. The cache is around 1Mbyte, so for a split-second > re-read of some data....
Apologies for the too brief answer. Sustained real world transfer rates for the PIIX4 under ideal setup conditions and a quiet bus are 14-18MB/s. Faster disk architecture and forcing ide driver parameters will not change this.
Here's what you might expect from this disk family with an ATA-66 capable chipset:
[tim@abit tim]# hdparm -i /dev/hda; hdparm -tT /dev/hda
/dev/hda:
Model=IBM-DTLA-307020, FwRev=TX3OA50C, SerialNo=YH0YHF45553 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=40 BuffType=DualPortCache, BuffSize=1916kB, MaxMultSect=16, MultSect=off CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=40188960 IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio1 pio2 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 *udma4 udma5
/dev/hda: Timing buffer-cache reads: 128 MB in 0.81 seconds =158.02 MB/sec Timing buffered disk reads: 64 MB in 1.85 seconds = 34.59 MB/sec
Larger sustained transfers are about 75% of the burst/cache influenced hdparm timings.
[tim@abit tim]# time dd if=/dev/hda of=/dev/null bs=1k count=500k 512000+0 records in 512000+0 records out 0.340u 6.780s 0:19.68 36.1% 0+0k 0+0io 115pf+0w [tim@abit tim]# echo "512000/19.68" | bc -q 26016
-- | 650.390.9613 | 6502247437@messaging.cellone-sf.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |