[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#22517: dd byte count report does not correlate with df byte count re
From: |
Bob Gustafson |
Subject: |
bug#22517: dd byte count report does not correlate with df byte count report |
Date: |
Sun, 31 Jan 2016 22:53:40 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 |
Description of problem:
I am trying to copy /root, /home from a single disk (running the os) to a
bigger raid 1 disk pair running in the same chassis.
fedora is the lvm vg_group of the running system, fedora23 is the lvm vg_group
of the new disks (raid 1, 2TB disks).
address@hidden user1]# lvscan
ACTIVE '/dev/fedora/swap' [15.57 GiB] inherit
ACTIVE '/dev/fedora/home' [865.45 GiB] inherit
ACTIVE '/dev/fedora/root' [50.00 GiB] inherit
ACTIVE '/dev/fedora23/swap' [15.60 GiB] inherit
ACTIVE '/dev/fedora23/root' [50.00 GiB] inherit
ACTIVE '/dev/fedora23/home' [1.75 TiB] inherit
Below is the command I'm using to copy over one partition to the raid pair:
address@hidden user1]# dd if=/dev/fedora/root of=/dev/fedora23/root
104857600+0 records in
104857600+0 records out
53687091200 bytes (54 GB) copied, 5639.3 s, 9.5 MB/s
address@hidden user1]#
address@hidden user1]# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 16G 0 16G 0% /dev
tmpfs 16G 392K 16G 1% /dev/shm
tmpfs 16G 1.8M 16G 1% /run
tmpfs 16G 0 16G 0% /sys/fs/cgroup
/dev/mapper/fedora-root 50G 27G 20G 58% /
tmpfs 16G 84K 16G 1% /tmp
/dev/loop0 1.9G 3.0M 1.7G 1% /srv/node/swift_loopback
/dev/mapper/fedora-home 852G 57G 752G 7% /home
/dev/sdc1 477M 215M 233M 48% /boot
tmpfs 3.2G 8.0K 3.2G 1% /run/user/42
tmpfs 3.2G 24K 3.2G 1% /run/user/1000
Note that dd says 54GB were copied over into a disk partition of size only
50GB. No errors during the copy. And the results show that only 27G was in the
fedora partition to start with. (54GB is double 27GB - this may be a clue)
Another example:
address@hidden user1]# dd if=/dev/fedora/home of=/dev/fedora23/home
1814978560+0 records in
1814978560+0 records out
929269022720 bytes (929 GB) copied, 32437.8 s, 28.6 MB/s
address@hidden user1]#
Taking a look at the data size on the target partitions:
address@hidden user1]# mount /dev/fedora23/root /mnt/rootn
address@hidden user1]# mount /dev/fedora23/home /mnt/homen
address@hidden user1]# du -h /mnt/rootn | tail -1
26G /mnt/rootn
address@hidden user1]# du -h /mnt/homen | tail -1
57G /mnt/homen
for the rootn partition, the 26G copied size is consistent with the source size.
For the homen partition, the 57G is consistent with the source size.
However, the count given by the dd copies don't match:
In the case of the root->rootn copy it is 54G instead of 27G
in the case of the home->homen copy it is 942G instead of 57G
Version-Release number of selected component (if applicable):
dd is (coreutils) 8.24
How reproducible:
I did two tests - as shown
Steps to Reproduce:
1. create raid 1 pair
2. copy a 3rd single disk partition to a raid1 pair lvm partition
3. do df and compare results.
Actual results:
As shown above in problem narative.
Expected results:
I would think that the sizes reported by dd and df would be comparable, but
they are not.
Additional info:
See also https://bugzilla.redhat.com/show_bug.cgi?id=1303456
- bug#22517: dd byte count report does not correlate with df byte count report,
Bob Gustafson <=