Re: resize2fs > 16TB questions

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On Jul 29, 2012, at 8:30 PM, Andreas Dilger wrote:

> 
> On 2012-07-29, at 9:46, Arne Hüggenberg <hueggenberg@xxxxxxxxxxxxxxxxx> wrote:
>> 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.
> 
> The overhead is relatively low. 
> 
>>> 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
>>       }
> 
> I think the "auto_64-bit_support" means that 64-byte group descriptors are not enabled for filesystems below 16TB. 
> 
>>>> 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?
> 
> Possibly with "debugfs stats"?

~ # debugfs /dev/vg0/lvol1 
debugfs 1.42.4 (12-June-2012)
debugfs:  stats
debugfs:  stats

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 extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
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:              2162482117
Free inodes:              520936736
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 20:50:44 2012
Mount count:              6
Maximum mount count:      -1
Last checked:             Fri Jul 27 17:16:24 2012
Check interval:           0 (<none>)
Lifetime writes:          7662 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
Directories:              6392
 Group  0: block bitmap at 2049, inode bitmap at 2065, inode table at 2081
           26585 free blocks, 4085 free inodes, 2 used directories, 4084 unused inodes
           [Checksum 0x7d46]
 Group  1: block bitmap at 2050, inode bitmap at 2066, inode table at 2337
           4634 free blocks, 4096 free inodes, 0 used directories, 4096 unused inodes
           [Inode not init, Checksum 0x97aa]
 Group  2: block bitmap at 2051, inode bitmap at 2067, inode table at 2593
           1020 free blocks, 4096 free inodes, 0 used directories, 4096 unused inodes
           [Inode not init, Checksum 0x571f]
 Group  3: block bitmap at 2052, inode bitmap at 2068, inode table at 2849
           2047 free blocks, 4096 free inodes, 0 used directories, 4096 unused inodes

> Cheers, Andreas
> 
>>>> ~ # 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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Regards,
Arne

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