Re: SES Enclosure Management.

[Joe Landman <joe.landman@gmail.com>]

On 02/14/2012 03:53 PM, Robert Woodworth wrote:
> On 02/14/2012 01:42 PM, Joe Landman wrote:
>> On 02/14/2012 03:31 PM, NeilBrown wrote:
>>> On Tue, 14 Feb 2012 10:30:37 -0700 Robert Woodworth
>>> <robertjwoodworth@gmail.com> wrote:
>>>
>>>> Has anyone ever thought of integrating SES managed enclosures into the
>>>> kernel RAID system? I briefly looked through the archives and have
>>>> not found anything on the topic.
>>>>
>>>> Some HW based RAID controllers do this flawlessly now, there is no
>>>> reason why the kernel RAID cannot also. (LSI MegaRAID)
>>>>
>>>> 1) When a drive is part if a managed enclosure, the RAID system should
>>>> address it by location instead of by enumerated device node. The SES
>>>> device in the enclosure can map the physical slot to a physical drive.
>>>> The RAID admin (mdamd) should be able to add/fail/identify devices
>>>> based on slot.
>>>
>>> Does this just mean that the admin should using names in
>>> /dev/disk/by-path/
>>> rather than /dev/sdXX to address devices? What can md or mdadm do to
>>> help?
>>>
>>
>> Not sure on the SES (or SGPIO side), but one of the things we've been
>> doing has been to create a file with disk placement "coordinates", so
>> as to map serial number and device to physical location.
>>
>
> With real SES managed enclosures, you issue a SCSI command to read SES
> Page1 and Page2 to get the details about the drives in any given slot.
> This currently works fine in Linux with the sg_utils3 package. From the
> command line, 'sg_ses -p 2 /dev/sgXX` where the device is the SES device.
>
> Take a look at your systems, if you see a device at
> /sys/class/enclosure/XXXX/ then you have a managed enclosure attached.
>

Got it.  Thanks.  Will look and see.  Should be pretty straight forward 
to do this.

>
>>>>
>>>> 2) If the RAID system fails a drive, it should notify the SES
>>>> management and turn on the fail bit and the fail LED.
>>>
>>> "mdadm --monitor" will run a script on drive failure. This could easily
>>> notify the SES management.
>>
>> Yes, we are using this now for notifications and logging.
>>
>>>
>>> So maybe all we need here is a script to plug in to mdadm... Would
>>> you like
>>> to write one?
>>>
>>
>> Just need a "standard" SES (or SGPIO) mechanism to hook into, and we
>> should be able to support this. Right now we have to work through HBA
>> scripts.
> A true managed enclosure has nothing to do with the HBA. A managed
> enclosure provides a device on the SCSI bus and you exclusively
> communicate with that device regardless of the HBA. Most HW RAIDs (LSI
> MegaRAID) will hide the SES device exactly like they hide the physical
> disks.
>

Ok.  Let me look to see if we can do this.  If so, we should be able to 
help contribute some scripts.
-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics Inc.
email: landman@scalableinformatics.com
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