Dear Matthew,

Some methods were not mentioned that have been discussed on zfs-discuss@
in the past several times. Useful for list archives at least:
. One easy way to detect disk locations is to make the lights blink if you
have lights per drive in your chassis. But it does not scale. For example
something similar to dd if=/dev/dsk/c0t5000CCA228C0E488d0 of=/dev/null
. Other methods have been discussed (check the archives), for example:
Quoting one example from above post by Richard:
> For the later Nexenta, OpenSolaris or Solaris 11 Express releases the
mpt_sas driver will try to light the
> OK2RM (ok to remove) LED for a disk when you use cfgadm to disconnect
the paths. Apparently this also
> works for SATA disks in an enclosure that manages SATA disks. The
process is documented very nicely
> by Cindy in the ZFS Admin Guide. However, there are a number of
enclosures that do not have an OK2RM

If you got other good pointers off-list, may I suggest to make a summary
for the list as this question pops up often.



[] On Behalf Of Matthew R.
Sent: Thursday, December 22, 2011 1:39 AM
Subject: Re: [zfs-discuss] Any rhyme or reason to disk dev names?

Thank you for all of the good pointers, everyone. croinfo and diskinfo
don't give me any output, but that's not surprising since this is a
home-built system. But it's good to know those utilities exist for
production hardware.

Making the association between the disk serial number and target number by
matching them up in the iostat -En or prtconf output looks like it will
work for me.

Thanks again!

On Wed, Dec 21, 2011 at 8:21 AM, Garrett D'Amore
<> wrote:

On Dec 21, 2011, at 3:14 AM, James C. McPherson wrote:

> On 21/12/11 05:58 PM, Matthew R. Wilson wrote:
>> Hello,
>> 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
>> 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
>> names are along the lines of:
>> /dev/dsk/c0t5000CCA228C0E488d0
>> 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
>> "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
>> to how to determine which port on my LSI controller card will
>> with which seemingly random device name. Can anyone offer any
>> on a way to predict the device naming, or at least get the system to
>> 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.

       - Garrett
> 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.
> hth,
> James C. McPherson
> --
> Oracle
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