disk is AWOL

[Dieter BSD]

>> 8.2 amd64
>> ad8 is a 3TB Seagate on nforce4-ultra controller
>>
>> At boot:
>> ad8: 2861588MB <ST3000DM001 9YN166 CC4B>> at ata4-master UDMA100 SATA 3Gb/s
>> DEBUG g_part_gpt.c gpt_read_hdr() ad8 succeeded with pp->>sectorsize=512
>>
>> An hour later:
>> # dd if=/dev/ad8 bs=4k count=1 of=/dev/null
>> dd: /dev/ad8: No such file or directory
>>
>> BUT: there was no "ad8: FAILURE - device detached" or similar message
>> on the console, in dmesg, or in /var/log/*.  The disk just disappeared
>> without a peep from the kernel. What's going on?

Frank writes:
> Is this repeatable? Does it appear when you reboot and then vanish
> after a period of time?

The disk reappeared after a reboot, and is still there working fine
(both read and write) after over 21 hours.

> At boot, what does "atacontrol list" say,

Before reboot:

ATA channel 4:
    Master:      no device present
    Slave:       no device present

After reboot:

ATA channel 4:
    Master:  ad8 <ST3000DM001-9YN166/CC4B> Serial ATA II
    Slave:       no device present

(It shouldn't even report a slave for the SATA ports, since SATA doesn't
*have* slaves.)

> and what about before and after you've tried to read from the drive?

No change, even after being up over 21 hours.