Help Diagnose Slow Disc Access

[Dave Stevens]

On Friday 19 February 2010 13:50:59 Mike McCarty wrote:
> Don Quixote de la Mancha wrote:
> > All of the hard drive vendors provide disk drive diagnostic tools,
> > that are able to access vendor-specific - and undocumented - firmware
> > in their drives.  This diagnostic firmware is able to diagnose drive
> > hardware problems in a much more thorough way than the vendor-neutral
> > S.M.A.R.T. is able to.
> >
> > These utilities are always provided in the form of DOS boot disk
> > images; one generally has a choice of making a floppy or a CD-ROM.
> 
> I downloaded said software, and burnt a CD-ROM. I ran the diagnostics
> on both discs (both are WDs, but of different sizes). The smaller
> one passed both a "quick" test, and an "extended" full surface scan
> test, and both in about the amount of time the tool estimated. The
> larger one (the one I'm having performance problems with) failed the
> "quick" test, due to timeout, after several times the estimated
> run time, but passed the "extended" full surface scan, though it took
> significantly longer than estimated. The estimated time was just over
> 15 hours, but the test ran 83 hours 33 minutes.
> 
> > Finally they all have a destructive test, in which the diagnostic
> > writes zeroes to every sector of the drive.
> 
> I did not try to run the destructive tests. There is one which performs
> a write test, and another which is not a test, but just intended to
> write zeros to all sectors.
> 
> > No matter what, if you think one of your drives might be flaky, back
> > them both up at once, before doing anything else.
> 
> That goes without saying.
> 
> > Being fully backed up also gives you the advantage that you can then
> > run the destructive sector-zeroing test.  I feel it's a good thing to
> > do in any case, just to "exercise the bits".
> 
> I'm not prepared to run another 83 hours non stop off line.
> 
> [...]
> 
> > Hope That Help,
> 
> Well, so far what the software has told me is that the disc appears
> to be OK, but very slow, which is what I already knew.
> 
> I want some help getting information out of the kernel to see what
> it thinks. Anyone familiar with how to do that?
> 
> I've wondered whether DMA might be disabled, or perhaps it's not
> running with interrupts, but hdparm seems to think that both drives
> are essentially running the same...
> 
> (ok drive)
> 
> # hdparm /dev/hda
> 
> /dev/hda:
>   multcount    = 16 (on)
>   IO_support   =  1 (32-bit)
>   unmaskirq    =  1 (on)
>   using_dma    =  1 (on)
>   keepsettings =  0 (off)
>   readonly     =  0 (off)
>   readahead    = 256 (on)
>   geometry     = 65535/16/63, sectors = 78165360, start = 0
> 
> (slow drive)
> 
> # hdparm /dev/hdb
> 
> /dev/hdb:
>   multcount    = 16 (on)
>   IO_support   =  1 (32-bit)
>   unmaskirq    =  1 (on)
>   using_dma    =  1 (on)
>   keepsettings =  0 (off)
>   readonly     =  0 (off)
>   readahead    = 256 (on)
>   geometry     = 38913/255/63, sectors = 625142448, start = 0
> 
> It's odd that hdparm is unable to notice that the disc is slow.

what does hdparm -tT /dev/hdb show?

Dave

> 
> Mike
>