linux-ext4 - large file system & high object count testing

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Date:	Mon, 31 Aug 2009 12:34:16 -0400
From:	Ric Wheeler <rwheeler@...hat.com>
To:	linux-ext4@...r.kernel.org, "Ted Ts'o" <tytso@...nk.org>
Subject: large file system & high object count testing


We have put together a very large, relatively slow JBOD to test 
scalability with (big server, 40GB of DRAM, 8 CPU's + 4 SAS expansion 
shelves, each with 16 2TB WD S-ATA drives).

In all, this is pulled together with DM (striped) to give us a bit over 
116TB.

Testing was done on 2.6.31-rc6 along with the pu branches e2fsprogs.

Everything went well until after the fsck - I think that I have 
reproduced that earlier issue with a failed mount.

mkfs took a very long time - longer than fsck. fsck (with around 500 
million 20KB files) finished in just under 2 hours.

logs below,

ric


[root@...adeth e2fsprogs]# time /sbin/mkfs.ext4 
/dev/vg_wdc_disks/lv_wdc_disks
mke2fs 1.41.8 (20-Jul-2009)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
4287627264 inodes, 31138512896 blocks
1556925644 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=33285996544
950272 block groups
32768 blocks per group, 32768 fragments per group
4512 inodes per group
Superblock backups stored on blocks:
     32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 
2654208,
     4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
     102400000, 214990848, 512000000, 550731776, 644972544, 1934917632,
     2560000000, 3855122432, 5804752896, 12800000000, 17414258688,
     26985857024

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 38 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

real    230m6.362s
user    2m30.844s
sys    200m1.002s
[root@...adeth e2fsprogs]# mount /dev/vg_wdc_disks/lv_wdc_disks /test_fs/
[root@...adeth e2fsprogs]# df -H /test_fs/
Filesystem             Size   Used  Avail Use% Mounted on
/dev/mapper/vg_wdc_disks-lv_wdc_disks
                        127T   256M   121T   1% /test_fs

FSCK time:

[root@...adeth e2fsck]# time ./e2fsck -f -tt /dev/vg_wdc_disks/lv_wdc_disks
e2fsck 1.41.8 (20-Jul-2009)
Pass 1: Checking inodes, blocks, and sizes
Pass 1: Memory used: 1280k/18014398508273796k (1130k/151k), time: 
4630.05/780.40/3580.01
Pass 1: I/O read: 126019MB, write: 0MB, rate: 27.22MB/s
Pass 2: Checking directory structure
Pass 2: Memory used: 1280k/18014398508921888k (65k/1216k), time: 
1215.10/454.21/705.79
Pass 2: I/O read: 34221MB, write: 0MB, rate: 28.16MB/s
Pass 3: Checking directory connectivity
Peak memory: Memory used: 1280k/18014398509445284k (65k/1216k), time: 
5884.30/1263.59/4295.71
Pass 3A: Memory used: 1280k/18014398509445284k (65k/1216k), time:  0.00/ 
0.00/ 0.00
Pass 3A: I/O read: 0MB, write: 0MB, rate: 0.00MB/s
Pass 3: Memory used: 1280k/18014398508921888k (56k/1225k), time:  1.49/ 
0.33/ 1.14
Pass 3: I/O read: 1MB, write: 0MB, rate: 0.67MB/s
Pass 4: Checking reference counts
Pass 4: Memory used: 1280k/724124k (56k/1225k), time: 91.59/89.70/ 1.88
Pass 4: I/O read: 0MB, write: 0MB, rate: 0.00MB/s
Pass 5: Checking group summary information
Pass 5: Memory used: 312k/200728k (56k/257k), time: 685.24/170.49/73.72
Pass 5: I/O read: 713MB, write: 0MB, rate: 1.04MB/s
/dev/vg_wdc_disks/lv_wdc_disks: 516142418/4287627264 files (0.0% 
non-contiguous), 2859838991/31138512896 blocks
Memory used: 312k/200728k (56k/257k), time: 6679.27/1541.45/4371.67
I/O read: 161012MB, write: 1MB, rate: 24.11MB/s

real    112m14.925s
user    25m41.557s
sys    73m46.849s


REMOUNT:

[root@...adeth e2fsck]# mount  /dev/vg_wdc_disks/lv_wdc_disks /test_fs/
mount: wrong fs type, bad option, bad superblock on 
/dev/mapper/vg_wdc_disks-lv_wdc_disks,
        missing codepage or helper program, or other error
        In some cases useful info is found in syslog - try
        dmesg | tail  or so

[root@...adeth ~]# tail -20 /var/log/messages
<snip>
Aug 31 12:27:12 megadeth kernel: EXT4-fs (dm-75): 
ext4_check_descriptors: Checksum for group 487 failed (59799!=46827)
Aug 31 12:27:12 megadeth kernel: EXT4-fs (dm-75): group descriptors 
corrupted!




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