Hello.
A ext4 file system is constantly writing to the block device with no
activity from the applications, is it a bug?
Write speed is about 64k bytes (almost always exactly 64k bytes) per
second every 1-2 seconds (I've discovered it after a RAID sync
finished). Please the check activity log sample below.
I could not find out which process was writing constantly, so I rebooted
to a rescue mode and mounted FS with no activity guaranteed - the same
activity has started about at 64kB/s every 1-2 seconds.
The file system was created with the latest e2fsprogs, here are the details:
Linux nexus 4.19.62 #2 SMP Sun Jul 28 17:18:10 CDT 2019 x86_64 AMD
Athlon(tm) Dual Core Processor 5050e AuthenticAMD GNU/Linux
# tune2fs -l /dev/<XXXXXXvg>/home
tune2fs 1.43.1 (08-Jun-2016) // file system was created in other system
with the latest version tools
Filesystem volume name: home
Last mounted on: /home
Filesystem UUID: XXXXXXXXXXXXXXXXXX
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 dir_nlink extra_isize metadata_csum
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 21644032
Block count: 2770432000
Reserved block count: 0
Free blocks: 2095699032
Free inodes: 21205431
First block: 0
Block size: 4096
Fragment size: 4096
Group descriptor size: 64
Reserved GDT blocks: 726
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 256
Inode blocks per group: 16
RAID stride: 128
RAID stripe width: 384
Flex block group size: 16
Filesystem created: Sat Jul 27 16:41:21 2019
Last mount time: Mon Jul 29 13:47:33 2019
Last write time: Mon Jul 29 13:47:33 2019
Mount count: 10
Maximum mount count: -1
Last checked: Sat Jul 27 16:41:21 2019
Check interval: 0 (<none>)
Lifetime writes: 2615 GB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 32
Desired extra isize: 32
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: XXXXXXXXXXXXXXXXXXXXXXX
Journal backup: inode blocks
Checksum type: crc32c
Checksum: 0x7f0fb170
BlockDev Activity log:
# iostat -kdt 1 /dev/XXXXXXvg/home
Linux 4.19.62 (XXXXX) 07/29/2019 _x86_64_ (2 CPU)
07/29/2019 02:08:03 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.91 15.40 37.77 19309 47364
07/29/2019 02:08:04 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:05 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:06 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:07 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:08 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:09 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:10 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:11 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:12 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:13 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:14 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:15 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:16 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:17 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:18 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:19 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:20 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:21 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:22 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
07/29/2019 02:08:23 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 0.00 0.00 0.00 0 0
07/29/2019 02:08:24 PM
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-5 1.00 0.00 64.00 0 64
Thank you,
---
Dmitrij Gusev
Systems architect
