Disk reliability (Was: Node cloning)

[Mark Hahn]

>   I hate to dredge up this topic again, but ... . I've got a machine
> with an IBM drive that is giving me the following errors,

it's not an error.

> kernel: hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
> kernel: hda: dma_intr: error=0x84 { DriveStatusError BadCRC }

translation: "the udma checksum detected a corrupt transaction
due to noise on the cable; it was automatically retried".

this *only* happens due to corruption of the signal on the cable;
normally, that's because someone has a bogus cable, or is overclocking.
if it happens at relatively low rate, there is no performance cost.

(for reference, all non-bogus IDE cables must be 18" or less,
with both ends plugged in (no stub).  for a mode > udma33,
the 80-conductor cable must also be used, and yes, it's still
at most 18".)

> as discussed in previous emails on the list. I followed the pointers
> that Josip gave and ran the IBM code on the drive. It said the drive

the code in question probably just configured the drive 
to default to udma33 or something modest.  this shouldn't ever
be necessary, since the bios shouldn't misconfigure a too-high
speed, and any modern Linux will not.  (though you can choose your
own mode using hdparm, if you wish.)