Re: large logical volumes

Guido Vettoretti <g.vettoretti@utoronto.ca> · Tue, 03 May 2005 12:42:31 -0400

Dan Pritts wrote:

  On Fri, Apr 29, 2005 at 04:35:02PM -0400, Guido Vettoretti wrote:

    32-bit machines:
ext3 : 2Tb (I managed to create a 4TB fs for some reason)

  I'm not sure this is true - i think that this limit was there but was
removed in newer versions of ext2/3

I haven't heard anything about the new versions but I was workiing with
kernel 2.6.9, and the number of block groups would roll over to 0 when
I specified a number greater than 32768. Thus the max limitation seemes
to be 4096(bytes/block)*32768(blocks/group)*32768(blockgroups) =  4TB 

[root@cyclone ~]# mkfs -t ext3 /dev/vol0/lvol0
mke2fs 1.35 (28-Feb-2004)
max_blocks 4294967295, rsv_groups = 0, rsv_gdb = 1024
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
512016384 inodes, 1024002048 blocks
8250429 blocks (0.81%) reserved for the super user
First data block=0
Maximum filesystem blocks=1027604480
31251 block groups
32768 blocks per group, 32768 fragments per group

    ext3: 2Tb (? not sure about this one)

I have created larger filesystems on 64-bit.

    One of the hardware support people said there was a 2Tb limit on the 
SCSI protocol (not sure about this), 

More or less true, but some newer hardware and device drivers 
have fixed this.  The keyword you need to look for is "64-bit LBA".

I've had success with an Atto celerity fibre channel adapter and
an infortrend-based RAID on x86_64.  However, each one needed a
firmware/driver update from what was shipped to me in December of
last year to work.

This is useful info,

Thanks

Guido

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