Sparse LUN scanning - 2.4.x

Sparse LUN scanning - 2.4.x

[Jim Zajkowski]

Hi there,

We have an Apple Xserve RAID, connected through a FC switch.  The RAID 
has LUN-masking enabled, such that one of our Linux boxes only gets LUN 
1 and not LUN 0.  We're running the 2.4.x kernel series now, since this 
is under a RHEL envinronment.

The problem is this: since LUN 0 does not show up -- specifically, it 
can't read the vendor or model informaton -- the kernel SCSI scan does 
not match with the table to tell the kernel to do sparse LUN 
scanning... so the RAID does not appear.

I can make the RAID show up by injecting a add-single-device to the 
SCSI proc layer.  Trivially patching scsi_scan.c to always do sparse 
scanning works as well.  No hokery with max_scsi_luns or ghost devices 
works.

I'm considering making a patch to add a kernel option to force sparse 
scanning.  Is there a better way?

Thanks in advance,

--Jim

-- 
Jim Zajkowski          OpenPGP 0x21135C3    http://www.jimz.net/pgp.asc
System Administrator  8A9E 1DDF 944D 83C3 AEAB  8F74 8697 A823 2113 5C53
UM Life Sciences Institute

 

Re: Sparse LUN scanning - 2.4.x

[Michael Clark]

Jim Zajkowski wrote:

> Hi there,
>
> We have an Apple Xserve RAID, connected through a FC switch.  The RAID 
> has LUN-masking enabled, such that one of our Linux boxes only gets 
> LUN 1 and not LUN 0.  We're running the 2.4.x kernel series now, since 
> this is under a RHEL envinronment.
>
> The problem is this: since LUN 0 does not show up -- specifically, it 
> can't read the vendor or model informaton -- the kernel SCSI scan does 
> not match with the table to tell the kernel to do sparse LUN 
> scanning... so the RAID does not appear.
>
> I can make the RAID show up by injecting a add-single-device to the 
> SCSI proc layer.  Trivially patching scsi_scan.c to always do sparse 
> scanning works as well.  No hokery with max_scsi_luns or ghost devices 
> works.
>
> I'm considering making a patch to add a kernel option to force sparse 
> scanning.  Is there a better way?
>
Add the Xserve with the BLIST_SPARSELUN flag into the blacklist/quirks 
table in drivers/scsi/scsi_scan.c

~mc

Re: Sparse LUN scanning - 2.4.x

[Jim Zajkowski]

On 2005-01-11 19:07:53 -0500, Michael Clark <michael@metaparadigm.com> said:

>> The problem is this: since LUN 0 does not show up -- specifically, it 
>> can't read the vendor or model informaton -- the kernel SCSI scan does 
>> not match with the table to tell the kernel to do sparse LUN 
>> scanning... so the RAID does not appear.

> Add the Xserve with the BLIST_SPARSELUN flag into the blacklist/quirks 
> table in drivers/scsi/scsi_scan.c

It already is in the quirks list.

The problem is that LUN 0 does not show up on this machine, so the 
quirks table doesn't work.  Looking at /proc/scsi/scsi shows the device 
but only sorta:

> Host: scsi1 Channel: 00 Id: 00 Lun: 00
>   Vendor:          Model:                  Rev:
>   Type:   Processor                        ANSI SCSI revision: ffffffff

whereas the LUN that is mapped shows up like this:

> Host: scsi1 Channel: 00 Id: 00 Lun: 01
>   Vendor: APPLE    Model: Xserve RAID      Rev: 1.20
>   Type:   Direct-Access                    ANSI SCSI revision: 02

So since the information doesn't show up, the quirks table magic 
doesn't work since it doesn't know that it needs to do a sparse lun 
scan.

--Jim

-- 
Jim Zajkowski          OpenPGP 0x21135C3    http://www.jimz.net/pgp.asc
System Administrator  8A9E 1DDF 944D 83C3 AEAB  8F74 8697 A823 2113 5C53
UM Life Sciences Institute

Re: Sparse LUN scanning - 2.4.x

[Michael Clark]

Jim Zajkowski wrote:

> On 2005-01-11 19:07:53 -0500, Michael Clark <michael@metaparadigm.com> 
> said:
>
>>> The problem is this: since LUN 0 does not show up -- specifically, 
>>> it can't read the vendor or model informaton -- the kernel SCSI scan 
>>> does not match with the table to tell the kernel to do sparse LUN 
>>> scanning... so the RAID does not appear.
>>
>
>> Add the Xserve with the BLIST_SPARSELUN flag into the 
>> blacklist/quirks table in drivers/scsi/scsi_scan.c
>
>
> It already is in the quirks list.
>
> The problem is that LUN 0 does not show up on this machine, so the 
> quirks table doesn't work.  Looking at /proc/scsi/scsi shows the 
> device but only sorta:
>

Okay. I believe there is a patch floating around for 2.4 that is used in 
some of the other distro's kernels that adds REPORT LUNS scanning as 
well as a flag to force LUN scanning (although not sure it works if LUN 
0 is not present).

A pragmatic solution may be to just add the echo scsi add-single-device 
x x x x > /proc/scsi/scsi into your early boot or configure one of your 
slices on LUN 0 (if the Xserve RAID allows that). 2.6 (and RHEL 4) 
support the REPORT LUNS so should work there although there are some 
messages on linux-scsi about the Xserve RAID's specific handling of LUN 
0. Probably good idea to post to linux-scsi.

~mc