Götz Reinicke - IT-Koordinator wrote:
Hi,
I'm trying to set up an iscsi 12.5 TB storage for some data backup.
Doing so, I had some difficulties to find the right tool, maybe it's
also a question of the system settings...
The server is a 32Bit Red Hat EL 5.3 with the recent updates. Ths iscsi
connection can be establised.
fdisk and parted fail to create any information on the device or fail
completely.
using the lvm tools (pvcreate, vgcreate, lvcreate), I could finaly
create a logical volume:
lvdisplay /dev/VolGroup02/lvol0
--- Logical volume ---
LV Name /dev/VolGroup02/lvol0
VG Name VolGroup02
LV UUID h7T6tD-JZw2-UEdb-q1ml-BDqp-9E0u-mAop6x
LV Write Access read/write
LV Status available
# open 0
LV Size 12,73 TB
Current LE 3337487
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:4
But, I can't create a filesystem on it:
mkfs.ext3 -m 2 -j -O dir_index -v -b 4096 -L iscsi2lvol0
/dev/mapper/VolGroup02-lvol0
mke2fs 1.39 (29-May-2006)
mkfs.ext3: Filesystem too large. No more than 2**31-1 blocks
(8TB using a blocksize of 4k) are currently supported.
The limits information provided by red hat say, that RH EL 5.1 supports
16 TB filesystems:
http://www.redhat.com/rhel/compare/
-> Maximum filesystem size (Ext3): 16TB in 5.1
Using a block size of 8192 gives a warning, that this size is to large
for that system.
So my question: What is my missunderstanding or what's wrong with my
system? Where are the real limits? Do I have to switch the OS to 64 Bit?
The problem is a limitation in ext2/ext3. With a PAGESIZE of 4kB (which is the
default on most PC architectures) the limit to the size of an ext2/ext3
filesystem is 8TB. If you are able to increase the PAGESIZE then you can
probably increase the max. filesystem size.
From some very cursory reading it seems that the Alpha, Itanium and PowerPC
processors may support larger PAGESIZE, but I am not certain of that. I don't
know whether the normal 4kB PAGESIZE is a hardware limit or just an optimal setting.
If you really do need a large filesystem then you will have to do some reading
up on whether your system can support a larger PAGESIZE. Otherwise you may be
able to split the external storage into multiple LUNs (if the hardware provides
that option) and create multiple smaller filesystems, one on each LUN.
--
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : nmw@xxxxxxxxxxxx
Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
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