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SubjectAbsolutely horrid IDE performance...
Date
I just installed an IBM Deskstar 10.1gig UDMA 7200rpm drive in one of my
Linux boxes (kernel 2.0.35, a SuperMicro P6SBA board with a Celeron 266, 4 x
100MHz). The IDE drive is currently the only IDE device and is not in use
(I'm running a Mylex BT-something or other and a SCSI Wide drive).

On /dev/hda:
hdparm gives 6.68meg/sec
time dd if=/dev/hda of=/dev/null bs=4096 count=16384 gives well under
1meg/sec (the more transfered the slower)

On /dev/sda (a junker Seagate WSCSI on the Mylex controller:
hdparm varies greatly between 2.5meg/sec and 4.5meg/sec
time dd... gives 4.6meg/sec

Can anyone explain the discrepancy? I can't see why there would be such a
huge difference. From what I've experienced with 95/NT machines, the IBM
UDMA drives are very fast. Linux even shows the system time required to be
reasonable between SCSI/IDE... it just seems like the drive is just running
slow (I thought it might be CPU overhead).

Thanks.
Brian Macy

/var/log/dmesg
ide: i82371 PIIX (Triton) on PCI bus 0 function 57
ide0: BM-DMA at 0xffa0-0xffa7
hda: IBM-DTTA-371010, 9641MB w/465kB Cache, CHS=1024/255/63, UDMA

#hdparm -I /dev/hda
/dev/hda:

Model=BI-MTDAT3-1710 0 , FwRev=7TO77AB0, SerialNo=
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=34
BuffType=3(DualPortCache), BuffSize=465kB, MaxMultSect=16, MultSect=off
DblWordIO=no, maxPIO=2(fast), DMA=yes, maxDMA=2(fast)
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=19746720
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

#time dd if=/dev/hda of=/dev/null bs=4096 count=16384
0.01user 0.38system 2:13.61elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (85major+11minor)pagefaults 0swaps
#time dd if=/dev/sda of=/dev/null bs=4096 count=16384
0.00user 0.20system 0:13.79elapsed 1%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (81major+11minor)pagefaults 0swaps


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