On Jul 29, 2012, at 6:11 PM, Andreas Dilger wrote:
> On 2012-07-29, at 8:24, Arne Hüggenberg <hueggenberg@xxxxxxxxxxxxxxxxx> wrote:
>>
>> im trying to resize a ext4 fs to > 16TB.
>
> Unfortunately, this is not possible today without advance planning. There are some structures on disk (group descriptors) that need to be larger for 64-bit filesystems. It is possible to format a 32-bit filesystem with larger group descriptors using the "-O 64bit" option, but this doesn't happen by default today.
>
> Possibly we should start using the 64-byte group descriptors by default for filesystems over, say, 4 TB, so they can be resized beyond 16 TB.
I have no idea what the overhead for 64byte group descriptors is, but with LVM Setups becoming more common and enabling incremental storage increases over a timeframe of several years, maybe 1TB filesystems should be cutoff.
> It might also be possible to modify resize2fs to change the group descriptor size, but that isn't possible today.
>
>> Having had a look at the e2fsprogs 1.42.x release notes i thought that, with the online resize ioctl having been merged in Kernel 3.3, this should be possible.
>>
>> But so far i have had no success achieving this:
>>
>> ~ # uname -a
>> Linux 3.3.8-gentoo #1 SMP Fri Jul 27 16:13:25 CEST 2012 x86_64 Intel(R) Xeon(R) CPU E5620 @ 2.40GHz GenuineIntel GNU/Linux
>>
>> ~ # tune2fs -l /dev/vg0/lvol1
>> tune2fs 1.42.4 (12-June-2012)
>> Filesystem volume name: <none>
>> Last mounted on: /home/filestore_extern_1
>> Filesystem UUID: 8fba4f1b-5311-4c9b-b8bf-def4957dc1bd
>> Filesystem magic number: 0xEF53
>> Filesystem revision #: 1 (dynamic)
>> Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
>
> Was the filesystem formatted with the 64bit option, or was this enabled after formatting time? This puts my earlier comment in doubt.
the filesystem was formatted with
from mke2fs.conf:
ext4 = {
features = has_journal,extent,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize,64bit
auto_64-bit_support = 1
inode_size = 256
}
>
>> Filesystem flags: signed_directory_hash
>> Default mount options: user_xattr acl
>> Filesystem state: clean
>> Errors behavior: Continue
>> Filesystem OS type: Linux
>> Inode count: 521011200
>> Block count: 4168089600
>> Reserved block count: 191127425
>> Free blocks: 2195165566
>> Free inodes: 520937830
>> First block: 0
>> Block size: 4096
>> Fragment size: 4096
>> Reserved GDT blocks: 60
>> Blocks per group: 32768
>> Fragments per group: 32768
>> Inodes per group: 4096
>> Inode blocks per group: 256
>> RAID stride: 16
>> RAID stripe width: 160
>> Flex block group size: 16
>> Filesystem created: Fri Jul 27 17:16:24 2012
>> Last mount time: Sun Jul 29 15:22:23 2012
>> Last write time: Sun Jul 29 15:22:23 2012
>> Mount count: 6
>> Maximum mount count: -1
>> Last checked: Fri Jul 27 17:16:24 2012
>> Check interval: 0 (<none>)
>> Lifetime writes: 7485 GB
>> Reserved blocks uid: 0 (user root)
>> Reserved blocks gid: 0 (group root)
>> First inode: 11
>> Inode size: 256
>> Required extra isize: 28
>> Desired extra isize: 28
>> Journal inode: 8
>> Default directory hash: half_md4
>> Directory Hash Seed: ef2ec72a-750b-4822-bd8d-9117faadeaee
>> Journal backup: inode blocks
>
> Unfortunately, the group descriptor size is not printed.
how can i get the group descriptor size?
>>
>>
>> ~ # resize2fs /dev/vg0/lvol1
>> resize2fs 1.42.4 (12-June-2012)
>> resize2fs: New size too large to be expressed in 32 bits
>
> This may just be a hard-coded check built into resize2fs, but may be over-zealous of the filesystem was formatted with -O 64bit.
>
>> Any advice on how to proceed would be welcome.
>>
>> Regards,
>> Arne
>>
>>
Regards,
Arne--
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