Landry Breuil wrote:
On Tue, Feb 03, 2009 at 10:59:10AM -0500, Jeff Garzik wrote:
Landry Breuil wrote:
Hi,
i encounter a very similar problem as reported in
http://marc.info/?l=linux-kernel&m=118764381013943&w=2, but with a SATA
disk. Trying to transfer 250Gb (mostly small files) from a SATA disk
(ata1/sda) to another (ata2/sdb), both plugged on the VT6421 card, after
some dozens of seconds the controler bails out and degrades write performance
(UDMA133->UDMA100->UDMA33...)
kernel: ata2.00: limiting speed to UDMA/33:PIO4
kernel: ata2.00: exception Emask 0x12 SAct 0x0 SErr 0x1400500 action 0x2 frozen
kernel: ata2: SError: { UnrecovData Proto Handshk TrStaTrns }
kernel: ata2.00: cmd 35/00:00:07:c6:f4/00:04:07:00:00/e0 tag 0 dma 524288 out
kernel: res 40/00:b0:27:1d:dc/84:00:07:00:00/e0 Emask 0x16 (ATA bus error)
Like Robert noted, this is the hardware complaining that it has found a
hardware error.
"SErr" stands for SATA SError register value. That is a value read
directly from hardware, which indicates one or more problems. Here is
some more info:
http://ata.wiki.kernel.org/index.php/Libata_error_messages#SATA_SError_expansion
When libata sees a bunch of hardware problems, it tries the only things
it can do to attempt progress in that situation: reset the hardware,
and slow down data transfer in an attempt to avoid errors again.
Okay, that makes sense. I swapped disks on the controller, and the
errors still pointed at the same disk. Will try with another disk..
the weird thing is that transferring files at a slow pace (from a
usb2 disk) shows no failure...
That is surprisingly normal, actually. Flaky hardware can often behave
100% normally, until you stress it.
Jeff
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