From: Eric Sandeen <sandeen@redhat.com>
To: Jan Engelhardt <jengelh@medozas.de>
Cc: linux-ext4@vger.kernel.org
Subject: Re: ext4 offers less blocks than other fs
Date: Tue, 15 Nov 2011 21:20:02 -0600 [thread overview]
Message-ID: <4EC32BE2.9080906@redhat.com> (raw)
In-Reply-To: <alpine.LNX.2.01.1111152031020.11901@frira.zrqbmnf.qr>
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On 11/15/11 1:51 PM, Jan Engelhardt wrote:
> Hi.
>
>
> In moving away from some ntfs-3g filesystem to ext4 (migration of a
> Windows-esque fileserver), I see a rather steep metadata use with ext4
> such that moving the data was not completely possible. Per df:
>
> Filesystem 1K-blocks Used Available Use% Mounted on
> /dev/dm-5 1953514324 1952543856 970468 100% /mnt/old
> /dev/mapper/data 1922858888 1922858880 0 100% /mnt/new
> [attempted a rsync as root]
>
> The blockdev size is just minimally different:
> 20:32 nas:~ # blockdev --getsize64 /dev/dm-5
> 2000398671872
> 20:32 nas:~ # blockdev --getsize64 /dev/dm-6
> 2000396836864
extN filesystems preallocate a lot of metadata, vs other filesystems
which may allocate this on the fly; that is what you are seeing.
> And there is a 29 GB(!) difference between 1953514324 and 1922858888,
> so my question is: where is all of that going?
Yongqiang Yang has it right; 7661170 + 32768 blocks for metadata
is right at 29G.
- -Eric
> (e2fsprogs 1.41.14)
> Filesystem volume name: data
> Last mounted on: /mnt/new
> Filesystem UUID: 807fec49-7a8a-3520-a648-be677475377c
> Filesystem magic number: 0xEF53
> Filesystem revision #: 1 (dynamic)
> Filesystem features: has_journal ext_attr resize_inode dir_index filetype
> needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg
> dir_nlink extra_isize
> Filesystem flags: signed_directory_hash
> Default mount options: (none)
> Filesystem state: clean
> Errors behavior: Continue
> Filesystem OS type: Linux
> Inode count: 122101760
> Block count: 488378134
> Reserved block count: 24418906
> Free blocks: 480664715
> Free inodes: 122101749
> First block: 0
> Block size: 4096
> Fragment size: 4096
> Reserved GDT blocks: 907
> Blocks per group: 32768
> Fragments per group: 32768
> Inodes per group: 8192
> Inode blocks per group: 512
> Flex block group size: 16
> Filesystem created: Mon Nov 14 20:43:23 2011
> Last mount time: Mon Nov 14 20:43:55 2011
> Last write time: Mon Nov 14 20:43:55 2011
> Mount count: 1
> Maximum mount count: 26
> Last checked: Mon Nov 14 20:43:23 2011
> Check interval: 15552000 (6 months)
> Next check after: Sat May 12 21:43:23 2012
> Lifetime writes: 144 MB
> 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: 5e2619e2-7683-4589-b390-57e569444705
> Journal backup: inode blocks
> Journal features: (none)
> Journal size: 128M
> Journal length: 32768
> Journal sequence: 0x00002751
> Journal start: 4341
> [Details about groups 0-14904 omitted.]
> --
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prev parent reply other threads:[~2011-11-16 3:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-15 19:51 ext4 offers less blocks than other fs Jan Engelhardt
2011-11-16 1:43 ` Yongqiang Yang
2011-11-16 3:20 ` Eric Sandeen [this message]
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