On 3 Apr 2009 at 11:42, Gonçalo Borges wrote:

> Is this 2048 GB limit imposed on iSCSI? Because there is nothing in SCSI
> itlself which forces you to this limit... Nowadays, you could have huge
> partitions (if you do GPT partitions with PARTED)... So, if there is a
> limit, it should come from iSCSI...

Hi, I just looked it up (use: "T10 SBC-2"): SCSI (See SBC-2, section 4.1) seems 
use "short LBA" (four bytes) and "long LBA" (eight bytes) to address blocks in 
block devices. So it seems our storage system only supports "short LBA". I 
know what Linux supports. I'd guess sizes up to 2^32-1 blocks are safe, however.

> >
> > > [r...@core26 ~]# fdisk -l /dev/sdb1
> > > Disk /dev/sdb1: 499.9 GB, 499999983104 bytes
> >
> > Isn't that a bit small for 2.7TB ? I think you should use fdisk on the
> > disk, not
> > on the partition!
> Here goes the output of fdisk on the disk:
>  [r...@core26 ~]# fdisk -l /dev/sdb
> WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk
> doesn't support GPT. Use GNU Parted.
> Disk /dev/sdb: 2998.9 GB, 2998998663168 bytes
> 255 heads, 63 sectors/track, 364607 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sdb1               1      267350  2147483647+  ee  EFI GPT

As the utility said, MS-DOS partitions can only handle partitions up to 2TB 
point something GB). I had little experience with parted yet, so you must find 
yorself. At least your utilities seem to do have done the right thing.

> We do GPT partitions with parted in order to overcome the deficienty of the
> (old!) 2048GB limit. Here goes the output of a parted (just to be sure):
> [r...@core26 ~]# parted /dev/mapper/iscsi06-apoio2
> GNU Parted 1.8.1
> Using /dev/mapper/iscsi06-apoio2
> Welcome to GNU Parted! Type 'help' to view a list of commands.
> (parted) print
> Model: Linux device-mapper (dm)
> Disk /dev/mapper/iscsi06-apoio2: 2999GB
> Sector size (logical/physical): 512B/512B
> Partition Table: gpt
> Number  Start   End    Size   File system  Name            Flags
>  1      17.4kB  500GB  500GB  ext3         iscsi06-apoio2

Ok, so your 500GB partition is at the start of the device. that should be safe 

> In principle, the partitition should be on the beguining of the logical
> volume but I can not confirm it with parted. If this is the case, everything
> shoudl work fine. However, If there is the limit of 2048 GB of storage per
> LUN, this may confuse the setup.. don't know for sure.

Now you'll have to compare the sector number Linux complains about (to be past 
end of the device / partition with the actual limit. Linux shouldn't access a 
device past the limit. Usually the commands that create filesystems do that 
correctly so that Linux shouldn't exceed the limits.

If there is an access outside the valid range, it could be some corruption vie 
iSCSI. You could use something like "dd if=/dev/zero 
of=a_big_file_in_your_filesystem" to fill your filesystem completely. Linux 
shouldn't complain about access past the end of the device. If it does, you'll 
have to dig further into details.


You received this message because you are subscribed to the Google Groups 
"open-iscsi" group.
To post to this group, send email to open-iscsi@googlegroups.com
To unsubscribe from this group, send email to 
For more options, visit this group at http://groups.google.com/group/open-iscsi

Reply via email to