HSV : ghosts & multipath

HSV : ghosts & multipath

[christophe varoqui]

Hello,

I read your contribution to scsidev, regarding HSV.
You seem to have an intimate knowledge of these controlers.
Do you happen to have a clue on how to force the activation of a ghost 
LUN from a Linux host ?

The rationale being : in a multipath config, when all active path are 
exhausted you should be able to activate the ghosts paths rather than 
let the device die.

More generally, how do you manage access to your HSV LUNs ? I personnaly 
would hate to use SecurePath which locks the user to one distribution 
and has not passed the "community peer-review test". Any alternative 
applicable in a dual fabric, dual attached hosts & controlers (4 
paths/host including 2 ghosts : 2 paths through the left fabric, 2 paths 
through the right) ?

Re: HSV : ghosts & multipath

[Evan Felix]

The HSV Ghost LUNS can be made active by sending the Start Unit Command
down the scsi path.  I have not had time to attempt to use this command,
and am not sure it can be sent to a Linux scsi device that is showing
'Not Ready'(Sense Code) and 'Not Connected'(Inquiry).  Other on this
list may be able to help us in this area.  Once you send this command
down, you will need to wait some amount of time while it flushes IO's
and changes controllers.

If you get this working i would love to see the results.

Evan


On Mon, 2003-08-11 at 16:03, christophe varoqui wrote:
> Hello,
> 
> I read your contribution to scsidev, regarding HSV.
> You seem to have an intimate knowledge of these controlers.
> Do you happen to have a clue on how to force the activation of a ghost 
> LUN from a Linux host ?
> 
> The rationale being : in a multipath config, when all active path are 
> exhausted you should be able to activate the ghosts paths rather than 
> let the device die.
> 
> More generally, how do you manage access to your HSV LUNs ? I personnaly 
> would hate to use SecurePath which locks the user to one distribution 
> and has not passed the "community peer-review test". Any alternative 
> applicable in a dual fabric, dual attached hosts & controlers (4 
> paths/host including 2 ghosts : 2 paths through the left fabric, 2 paths 
> through the right) ?
-- 
-------------------------
Evan Felix
Environmental Molecular Sciences Laboratory
Pacific Northwest National Laboratory
Operated for the U.S. DOE by Battelle

Re: HSV : ghosts & multipath

[christophe.varoqui]

Hello,

sg_start, which comes with latest sg3_utils, does the trick, indeed.
Thanks for the tip.

Selon Evan Felix <evan.felix@pnl.gov>:

> The HSV Ghost LUNS can be made active by sending the Start Unit Command
> down the scsi path.  I have not had time to attempt to use this command,
> and am not sure it can be sent to a Linux scsi device that is showing
> 'Not Ready'(Sense Code) and 'Not Connected'(Inquiry).  Other on this
> list may be able to help us in this area.  Once you send this command
> down, you will need to wait some amount of time while it flushes IO's
> and changes controllers.
> 
> If you get this working i would love to see the results.
> 
> Evan
> 
> 
> On Mon, 2003-08-11 at 16:03, christophe varoqui wrote:
> > Hello,
> > 
> > I read your contribution to scsidev, regarding HSV.
> > You seem to have an intimate knowledge of these controlers.
> > Do you happen to have a clue on how to force the activation of a ghost 
> > LUN from a Linux host ?
> > 
> > The rationale being : in a multipath config, when all active path are 
> > exhausted you should be able to activate the ghosts paths rather than 
> > let the device die.
> > 
> > More generally, how do you manage access to your HSV LUNs ? I personnaly 
> > would hate to use SecurePath which locks the user to one distribution 
> > and has not passed the "community peer-review test". Any alternative 
> > applicable in a dual fabric, dual attached hosts & controlers (4 
> > paths/host including 2 ghosts : 2 paths through the left fabric, 2 paths 
> > through the right) ?
> -- 
> -------------------------
> Evan Felix
> Environmental Molecular Sciences Laboratory
> Pacific Northwest National Laboratory
> Operated for the U.S. DOE by Battelle
> 
> 


-- 

Re: HSV : ghosts & multipath

[Evan Felix]

Doh!..  i forgot to answer your second question:

On Mon, 2003-08-11 at 16:03, christophe varoqui wrote:
> More generally, how do you manage access to your HSV LUNs ? I personnaly 
> would hate to use SecurePath which locks the user to one distribution 
> and has not passed the "community peer-review test". Any alternative 
> applicable in a dual fabric, dual attached hosts & controlers (4 
> paths/host including 2 ghosts : 2 paths through the left fabric, 2 paths 
> through the right) ?
> 

I Do not have a full solution yet, but the things we have looked at are:

1. Qlogic 2300 failover driver, which did seem to work fairly well when
you have two active paths.  does not understand the ghost issues at all.

2. The linux md multipath driver works fairly reliable, but also does
not understand ghost devices.

3. Do nothing.  This is actually what we are doing now, as we
investigate the other options.  In a failure situation the plan is to
re-load the qlogic modules, re-run scsidev which will remap the failed
disks to the correct position.

I am still waiting on a usuable version of SecurePath for IA64, and have
not seen even the beta yet....  since HP is supporting our box we may be
able to get more access to the code and have them tailor a version for
our specific kernel and software config.  Maybe.

Hope that helps.

Evan