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JEO
2008-07-16, 06:26 PM CDT
I notice my hard disk access speeds were poor afer a suspend/resume. I found out why. At boot time the transfer mode is set to:

Excerpt from hdparm -i /dev/sda

PIO modes: pio0 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5


Excerpt from hdparm -I /dev/sda after a suspend/resume cycle:

DMA: mdma0 mdma1 *mdma2 udma0 udma1 udma2 udma3 udma4 udma5
Cycle time: min=120ns recommended=120ns
PIO: pio0 pio1 pio2 pio3 pio4

Notice the crummy mdma2 mode it's in. It should be in udma5 mode. My question is, besides rebooting, how can I change it back? hdparm -d returns nothing, no dma setting (probably because they are the new libata drivers).

Edit: running FC8 32 bit, all current updates. Drives are PATA 80GB Western Digitals (I have 2 in a mirror and the results for /dev/sdb is the same as /dev/sda).

JEO
2008-07-16, 06:53 PM CDT
I just tried:

[root@localhost ~]# hdparm -X udma5 /dev/sda

/dev/sda:
setting xfermode to 69 (UltraDMA mode5)
SG_IO: bad/missing ATA_16 sense data:: 70 00 05 00 00 00 00 0a 00 00 00 00 24 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
HDIO_DRIVE_CMD(setxfermode) failed: Input/output error

So that isn't going to work. Any ideas?