On Dec 21, 2011, at 3:14 AM, James C. McPherson wrote:
> On 21/12/11 05:58 PM, Matthew R. Wilson wrote:
>> I am curious to know if there is an easy way to guess or identify the
>> device names of disks. Previously the /dev/dsk/c0t0d0s0 system made sense
>> to me... I had a SATA controller card with 8 ports, and they showed up
>> with the numbers 1-8 in the "t" position of the device name.
>> But I just built a new system with two LSI SAS HBAs in it, and my device
>> names are along the lines of:
>> I could not find any correlation between that identifier and the a)
>> controller the disk was plugged in to, or b) the port number on the
>> controller. The only way I could make a mapping of device name to
>> controller port was to add one drive at a time, reboot the system, and run
>> "format" to see which new disk name shows up.
>> I'm guessing there's a better way, but I can't find any obvious answer as
>> to how to determine which port on my LSI controller card will correspond
>> with which seemingly random device name. Can anyone offer any suggestions
>> on a way to predict the device naming, or at least get the system to list
>> the disks after I insert one without rebooting?
> Hi Matthew,
> By default the names for disks attached via mpt_sas(7d), or
> mpt(7d) if your disks are new enough, is to use their WWN
> as reported in the SCSI INQUIRY Page83 response.
> The old paradigm you refer to is based on the physical id
> of the device on a parallel SCSI bus. That doesn't scale
> with SAS, and is something we're trying to move away from.
More to the point, on SAS and other similar busses, there simply *isn't* such a
thing as a simple target number. The old numbering scheme from parallel SCSI
was suitable when you could have only 7 or 15 or so devices on a single bus.
With modern busses you can have many thousands of devices on the same fabric.
So we address them by WWN.
> If you'd like some info about how we use devids and guids,
> please refer to my presentation
> For your particular configuration, if you note the serial
> number and WWN of the device before you insert them, you
> can match that up with info from iostat -En and/or prtconf -v.
> James C. McPherson
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