How to map between /dev/sdX and dev/sgX devices?

How to map between /dev/sdX and dev/sgX devices?

[Reilley, Peter]

What is the correct way to find the corresponding scsi generic
device given the scsi disk node name?   I have a situation
where I must issue SCSI pass thru commands to a specific
/dev/sdX node.   I must find the correct /dev/sgX node is a 
situation where the system may go through a scsi reconfiguration
that would alter the mapping.   This is in a system where there 
could be a hundred scsi devices.

In my case this is related to iscsi but the problem is not
limited to iscsi.   Is there any good way of getting this
mapping.

Thanks,
Pete.

Re: How to map between /dev/sdX and dev/sgX devices?

[Arjan van de Ven]

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On Thu, 2004-08-19 at 20:35, Reilley, Peter wrote:
> What is the correct way to find the corresponding scsi generic
> device given the scsi disk node name?   I have a situation
> where I must issue SCSI pass thru commands to a specific
> /dev/sdX node.  

don't..... use SG_IO on the device directly

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Re: How to map between /dev/sdX and dev/sgX devices?

[Douglas Gilbert]

Arjan van de Ven wrote:
> On Thu, 2004-08-19 at 20:35, Reilley, Peter wrote:
> 
>>What is the correct way to find the corresponding scsi generic
>>device given the scsi disk node name?   I have a situation
>>where I must issue SCSI pass thru commands to a specific
>>/dev/sdX node.  
> 
> 
> don't..... use SG_IO on the device directly

and if that breaks your app then try the equivalent
sg device to check that you haven't tripped over another
QOI issue.

Doug Gilbert

Re: How to map between /dev/sdX and dev/sgX devices?

[Bryan Henderson]

>> don't..... use SG_IO on the device directly
>
>and if that breaks your app then try the equivalent
>sg device to check that you haven't tripped over another
>QOI issue.

What is QOI?

RE: How to map between /dev/sdX and dev/sgX devices?

[Reilley, Peter]

> -----Original Message-----
> From: Arjan van de Ven [mailto:arjanv@redhat.com]
> Sent: Thursday, August 19, 2004 3:13 PM
> To: Reilley, Peter
> Cc: linux-scsi@vger.kernel.org
> Subject: Re: How to map between /dev/sdX and dev/sgX devices?
> 
> 
> On Thu, 2004-08-19 at 20:35, Reilley, Peter wrote:
> > What is the correct way to find the corresponding scsi generic
> > device given the scsi disk node name?   I have a situation
> > where I must issue SCSI pass thru commands to a specific
> > /dev/sdX node.  
> 
> don't..... use SG_IO on the device directly
> 

I don't think that this will work for me.
I must support the 2.4 kernel as well as the 2.6 kernel.

Thanks,
Pete.

Re: How to map between /dev/sdX and dev/sgX devices?

[Brian King]

Reilley, Peter wrote:
>>-----Original Message-----
>>From: Arjan van de Ven [mailto:arjanv@redhat.com]
>>Sent: Thursday, August 19, 2004 3:13 PM
>>To: Reilley, Peter
>>Cc: linux-scsi@vger.kernel.org
>>Subject: Re: How to map between /dev/sdX and dev/sgX devices?
>>
>>
>>On Thu, 2004-08-19 at 20:35, Reilley, Peter wrote:
>>
>>>What is the correct way to find the corresponding scsi generic
>>>device given the scsi disk node name?   I have a situation
>>>where I must issue SCSI pass thru commands to a specific
>>>/dev/sdX node.  
>>
>>don't..... use SG_IO on the device directly
>>
> 
> 
> I don't think that this will work for me.
> I must support the 2.4 kernel as well as the 2.6 kernel.

Does sg_map work for you?

-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center