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 CentOS 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?
>
> Setting up large Filesystems isn't my staff of life :-)
>
>
> Thanks for amy how to or help of any kind - Best regards,
>
> Götz
>
>
Gotz,
YMMV, but XFS is what I would use (and do use) as a filesystem in this
instance. There are caveats, some of which are listed here:
1) Server/storage must be on stable power, backed up by a ups. I have
never dealt with XFS filesystem corruption, but I have read anecdotal
horror stories.
2) You need to run 64 bit, if for no other reason than memory requirements.
3) You will need to have a partition that can be used as swap space. I
have not found any consistent formula, but I am running multiple servers
using XFS, with 12gig of ram, 9TB filesystem, and 12 gigs was not enough
memory to run xfs_check, which you should do on occasion. I wound up
making a 20gig swap space on a separate partition while I was running
xfs_check. That may have been excessively large, but it worked...
4) XFS is not (or has not been) part of the standard RHEL distro, so
you lose the 1:1 aspects of running CentOS when you implement XFS.
My experience has been that XFS is quite a bit faster than ext3,
especially during file manipulation procedures. Others may not agree.
It has proven rock-solid for me, both in the linux world and IRIX.
Below is a link discussing the need for 64bit vs. 32bit (a bit old but
still relevant):
http://oss.sgi.com/archives/xfs/2005-08/msg00391.html
Hope this helps.
Monty
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