Unused sectors are included in backups of EXT4 and XFS partitions on physical Linux servers.

Unused sectors are included in backups of EXT4 and XFS partitions on physical Linux servers.

Article: 100043989
Last Published: 2019-02-25
Ratings: 0 0
Product(s): System Recovery

Problem

Unused sectors are included in backups of EXT4 and XFS partitions on physical Linux servers (virtual machines are not affected). This means that the size of the recovery point (v2i file) is much larger than expected.

An example is a backup of an EXT4 partition that is 50GB in size with 3GB of used space produces a v2i file of 37GB.

Error Message

N/A

Cause

Regarding EXT4, Red Hat or CentOS enables 64bit file system feature by default. Without disabling 64bit file system feature, System Recovery cannot get the recovery point file size as expected.

Regarding XFS, Red Hat or CentOS enables Metadata cyclic redundancy checks (CRC) feature by default. Without disabling CRC feature, System Recovery cannot get the recovery point file size as expected.

Solution

This is by design. Please perform the below workaround in each file system in order to avoid backups for unused sectors.


Workaround for EXT4:


If your volume is less than 16TB, 64bit file system feature can be disabled. To disable 64bit file system feature, e2fsprogs-1.43 or later is required but even Red Hat 7.4/7.5 or CentOS 7.4/7.5 does not implement e2fsprogs-1.43 yet. If e2fsprogs-1.43 or later is manually installed on the system, please perform below steps as a workaround. 

  1. Unmount the backup source device. (Example: umount /dev/sdc1)
  2. Run “e2fsck -f /dev/sdc1”.
  3. Run “resize2fs -s /dev/sdc1”.

Note: e2fsprogs-1.43 or later needs to be installed in order to use -s option. 

  1. Mount the device again.
  2. Backup the device and verify the recovery point file size. 


Workaround for XFS:


To disable CRC feature, the device has to be formatted and the existing data will be deleted. If the device can be formatted, please perform the below steps.

  1. If the existing data in the backup source device needs to be kept , backup all data.
  2. Unmount the backup source device. (Example: umount /dev/sdc1)
  3. Run “mkfs.xfs –f –m crc=0 /dev/sdc1” if the backup source device is /dev/sdc1. 

CAUTION: This is a command to format /dev/sdc1. Hence the existing folders and files will be deleted.

  1. Mount the device. 
  2. If needed, restore the backed up data to the backup source device with files/folders level.
  3. Backup the device and verify the recovery point file size. 
     

References

Etrack : 3957625

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