[ale] Bad Hard Drive

[Michael Trausch]

It is possible that nondeterminism depends on the SATA chipset, but I have a
system in production where the drives are enumerated in the order they
appear to the kernel. Furthermore... if I pull sdb out (yay hot swap) and
put it back in, it'll get sdg (sdf is the last one assigned at boot time in
this system).

I don't really worry about it, though, because I use the serial numbers, not
the node names.

--
Sent from my phone... a G2 running CM7 nightlies!
On Jun 16, 2011 4:56 PM, "David Tomaschik" <david at systemoverlord.com> wrote:
> On Thu, Jun 16, 2011 at 4:38 PM, Jim Kinney <jim.kinney at gmail.com> wrote:
>> Sort of but not quite all correct. The hard drive chain was not changed
>> totally. Non-deterministic for pci-bus devices but still traceable with
>> lspci. Always non-d for usb (pita)
>>
>> Hard drives follow a specific pattern:
>>
>> BIOS spills data to sys about drive locations. Bus num followed by device
>> num. That doesn't change 'cause it can't.
>>
>> If a new drive is inserted at a lower bus num  than other drives, it gets
>> called sda. Move the drive in socket 0 to socket 5 and it now is called
sdf.
>>
>> But so what?! Most distros use UUID anyway so you can move your drives
>> around between boots and it'll still work as long as the BIOS knows where
>> the /boot drive is. Cool thing is error messages will reflect the current
>> configuration.
>>
>> So if the bad drive is moved from sdb to sdf, on reboot the error will
>> reflect the bad drive is sdf.
>>
>> So as long as drives stay plugged in the same, detection will be
>> deterministic but the name is not. Remember, empty sockets 0-5 and a
single
>> drive in 5 will be called sda.
>>
>> Thus by looking for the next to lowest numbered drive will reveal sdb,
the
>> failed drive in the OP. :-)
>
> Unless, of course, there are udev rules that specify otherwise.
> Serial # is still the most reliable way to be CERTAIN of what you're
> pulling. Removing the wrong drive from a RAID can make your day very
> bad. (I've placed SN labels on the visible end of drives in my home
> system for exactly this reason. Or paranoia. Or because I like
> labels. Take your pick.)
>
>
>
> --
> David Tomaschik, RHCE, LPIC-1
> System Administrator/Open Source Advocate
> OpenPGP: 0x5DEA789B
> http://systemoverlord.com
> david at systemoverlord.com
>
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