[stgt] [linux-iscsi-users] 2TB+ LUNs?

[Ray Van Dolson]

On Tue, Jan 27, 2009 at 02:37:48PM -0800, Richard Sharpe wrote:
> On Tue, Jan 27, 2009 at 12:57 PM, Mike Christie <michaelc at cs.wisc.edu> wrote:
> >
> > Ray Van Dolson wrote:
> >>
> >> Hello all, I'm running the iscsi-initiator-utils package v4.0.3.0
> >> (included with RHEL4) and trying to link up to a 2TB LUN exported from
> >> a RHEL5.2 machine using STGT (0.20070620snap).
> >>
> >> The RHEL4 machine is running 32-bit while the RHEL5 machine is 64-bit.
> >>
> >> When I log in to the target, I see the following in dmesg:
> >>
> >>  iscsi-sfnet:host2: Session established
> >>  scsi2 : SFNet iSCSI driver
> >>  scsi: unknown device type 12
> >>    Vendor: IET       Model: Controler         Rev: 0001
> >>    Type:   RAID                               ANSI SCSI revision: 05
> >>  Attached scsi generic sg2 at scsi2, channel 0, id 0, lun 0,  type 12
> >>    Vendor: IET       Model: VIRTUAL-DISK      Rev: 0001
> >>    Type:   Direct-Access                      ANSI SCSI revision: 05
> >>  sdb : very big device. try to use READ CAPACITY(16).
> 
> This means that the kernel wanted to treat the device as larger than 2TiB.
> 
> >>
> >>  sdb : READ CAPACITY(16) failed.
> 
> It tried to send a READ CAPACITY (16) which is a 16-byte CDB.
> However, the SCSI LLD that is the initiator has to set the size of
> the largest CDBs it accepts, and the default is 12, as I recall. So,
> if the LLD does not override the max CDB size, I think they do not
> even make it to the (remote) device
> 
> Are there any weird messages on the target about short CDBs or
> malformed CDBs? That might help.
> 
> I went through this a while ago with 2.6.19 and the USB Storage LLD
> ...

Thanks for the reply Richard.

I don't see anything at all really in the target's syslogs, nor in
dmesg.  I ran tgtd in debug mode in the foreground, but it was very
noisy (obviously) and I wasn't really sure what I was looking for.

I've also taken a packet dump of a connection.  Maybe someone can find
something useful from it?

Any other suggestions on how to troubleshoot?  I'm guessing if I drop
below 2TB for my LUN's this would work for sure...

Guess I could open a SR with Red Hat to look into this.

Ray

> 
> >>  sdb : status=1, message=00, host=0, driver=08  sdb : use 0xffffffff as device size
> >>  SCSI device sdb: 4294967296 512-byte hdwr sectors (2199023 MB)
> >>  SCSI device sdb: drive cache: write back
> >>  sdb : very big device. try to use READ CAPACITY(16).
> >>  sdb : READ CAPACITY(16) failed.
> >>  sdb : status=1, message=00, host=0, driver=08  sdb : use 0xffffffff as device size
> >>  SCSI device sdb: 4294967296 512-byte hdwr sectors (2199023 MB)
> >>  SCSI device sdb: drive cache: write back
> >>   sdb: unknown partition table
> >>  Attached scsi disk sdb at scsi2, channel 0, id 0, lun 1
> >>  Attached scsi generic sg3 at scsi2, channel 0, id 0, lun 1,  type 0
> >>
> >> My question is -- are 2TB and larger LUNs supported with this
> >> initiator?  If so, how?
> >
> > The initaitor is just passing around data. Those messages come from
> > the scsi layer's sd_mod.
> >
> > With RHEL4's iscsi/scsi code I have setup luns bigger than 2 TB. We
> > have a 4 TB one here.
> >
> > There is a bug in RHEL4, where if you have exactly a 2 TB lun then
> > it will not get detected right (this is with iscsi, fc, spi).
> >
> > ccding the stgt list to make sure that it supports large luns.
> >
> > What vesion of RHEL is this? Is it 4.0 or 4.4?
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> 
> 
> 
> --
> Regards,
> Richard Sharpe
> 

Ray
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