> My main drive with all Linux files on it is a WD 4.3g UDMA 33 model. I have
> UDMA turned on for this drive (again, a program from WD web site). Using
> "hdparm" to check that dma mode is turned on for _both_ drives (turned on
> automatically by option in make config), I get 12 to 13 MB/sec on the WD.
> Using "hdparm" on the IBM drive, I get 17 MB/sec. Granted, 17 is faster than
> 13, but is it UDMA 66?
Similar to Tom Livingson's preface I claim much experience with EIDE and
U/33 controller but no hands on U/66. That being said, the facts: a
U/66 controller and disk will not yield 2x U/33 performance regardless
of Promise marketing BS. Here's a real example
(http://www.storage.ibm.com/hardsoft/diskdrdl/desk/2522data.htm).
IBM's spec sheet has a performance section as do other manufacturers.
There are three measurements that predict actual performance:
1. Media transfer rate (bits off the platters).
2. Interface transfer rate (also called burst rate) (bits out of onboard
cache).
3. Sustained data rate (what you'll see if everything is perfect).
The example is a Deskstar 22GXP. UDMA-4, 7200RPM, 2MB cache with a
sustained rate of 17MB/s.
I have a pair of 14GXP's. UDMA-2, 7200RPM, 512KB cache and a top end
sustained of 13MB/s. Here it is on an Asus P2B-F:
[tim@asus tim]# hdparm -itT /dev/hdh
/dev/hdh:
Model=IBM-DTTA-371440, FwRev=T71OA73A, SerialNo=WK0WK0F8
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=28005/16/63, TrkSize=0, SectSize=0, ECCbytes=34
BuffType=3(DualPortCache), BuffSize=462kB, MaxMultSect=16, MultSect=off
DblWordIO=no, maxPIO=2(fast), DMA=yes, maxDMA=2(fast)
CurCHS=28005/16/63, CurSects=28229040, LBA=yes, LBAsects=28229040
tDMA={min:120,rec:120}, DMA modes: sword0 sword1 sword2 mword0 mword1
mword2
IORDY=on/off, tPIO={min:240,w/IORDY:120}, PIO modes: mode3 mode4
Timing buffer-cache reads: 64 MB in 0.48 seconds =133.33 MB/sec
Timing buffered disk reads: 32 MB in 2.54 seconds =12.60 MB/sec
[/proc/pci output]
...
Bus 0, device 10, function 0:
RAID storage controller: Promise Technology IDE UltraDMA/33 (rev 1).
Medium devsel. IRQ 3. Master Capable. Latency=32.
I/O at 0xb800.
I/O at 0xb404.
I/O at 0xb000.
I/O at 0xa804.
I/O at 0xa400.
2.0.37 kernel.
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