ATA READ command timeout (and worse)

[Stephen McKay]

On Tuesday, 17th June 2003, Axel Simon wrote:

>On Wed, Jun 18, 2003 at 12:53:18AM +1000, Stephen McKay wrote:
>> I've been plagued by ATA READ command timeouts on my home NFS server.
>> Tonight I decided to get to the bottom of it, so I started torturing
>> it. :-)

>If your disks make some clicking noises, they are probably overheated.  
>Once a disk gets too hot it can take permanent damage as the head scrapes
>off some material from the surface which gets in the way of the head which
>then cannot move freely.

They don't make clicking noises.  I don't think they are too hot either.
If I put my hand on the flat top of each disk, they are comforably warm.
When I put my hand on the edge, it is noticeably warmer, but not burning.
An inexpensive digital thermometer says the hottest point on the hottest
drive is 33.7 degrees celsius.  That's not hot.

>> Jun 17 22:28:02 peon /kernel: ad6: READ command timeout tag=0 serv=0 - resetting
>> Jun 17 22:28:02 peon /kernel: ata3: resetting devices .. done
>> ...
>> Jun 17 23:05:03 peon /kernel: ad4: READ command timeout tag=0 serv=0 - resetting
>> Jun 17 23:05:03 peon /kernel: ata2: resetting devices .. ad4: DMA limited to UDMA33, non-ATA66 cable or device
>> Jun 17 23:05:03 peon /kernel: done
>This could be the disk getting too hot. It's IDE, so it tries to deal with 
>all problems itself. AFAIK there is no way the disk can actually 
>communicate more informative error messages to the driver.

There may be some weird internal error it's not reporting.  But it can't
be heat causing it.

>> Note the cable most certainly IS ATA66 (and ATA100) capable, and correctly
>> connected.  Note that at boot time ad4 is NOT limited to UDMA33.
>I've heard people complaining about low-quality cables. Make sure they are 
>short, preferably twist'n'flat cables (round and shielded between the 
>ribbon connectors). But if...

I used the flat ribbon cables that came with the SiI 0680.  Then I bought
shielded rounded cables.  They made no difference, good or bad (but look
cool :-).  Also I get no ICRC errors, which you might expect with low
quality cables.

>> The power supply has 230W written on it, and I'm assuming that (like
>> nearly all power supplies) it's an optimistic value.  I really don't
>> want to take the whole thing apart so I'm hoping someone finds an ata
>> driver bug!
>I don't think you need to. 230W = 5V * 20 A + 12V * 10A + ... Each drive 
>says how much it needs which is about 1.2A maximum (i.e. when it powers 
>up). If the power supply would be too weak, then it would get too hot and 
>switch off for some time (also on the 5V line which will reset the PC).

Nothing weird happens at powerup.  Also the top of the power supply feels
cold to the touch, not even warm.  So I suppose I don't have a power supply
problem.

>Make sure you have one drive's worth of space between each pair of hard 
>disks. If you can't touch the hard disk from all sides without burning 
>yourself, they are too hot.

I have a 1cm gap between the closest two drives.  I expect that's enough.

By the way, this brings another question to mind.  My understanding is
that all S.M.A.R.T. capable drives have internal temperature sensors.
How do I access this info using FreeBSD?

Stephen.