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

[Richard Sharpe]

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 ...

>>  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
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