Have a MySQL (percona, 14.14 Distrib 5.6.28-76.1) machine with a 1TB SSD hosting around 712Gb of mysql data. MySQL has 4 databases, with, say database1, taking major space, 656Gb. Lets call this machine machine1.
Want to rebuild another MySQL DB machine, say, machine2, which has exact same configuration. So took an LVM Snapshot on machine1.
df -h command will show the following output for the MySQL and LVM partitions:
On Machine1, after taking LVM snapshot: /dev/mapper/vgmysql-mysql_tmp 100G 33M 100G 1% /var/tmp/mysql /dev/mapper/vgmysql-mysql 900G 713G 188G 79% /var/lib/mysql /dev/mapper/vgmysql-mysql_snapshot 900G 713G 188G 79% /var/cache/mylvmbackup/mnt/backup /dev/mapper/vgroot-mysql_backup 905G 33M 905G 1% /var/cache/mylvmbackup/backup
Mounted the SSD partition of machine2 (/var/lib/mysql) onto machine1 using NFS export mount option, and did an rsync from the LVM snapshot to the remote mount. After mounting the remote partition and doing the rsync, df -h showed the following output on machine1.
On Machine1, after rsyncing to Machine2's remote mount: /dev/mapper/vgmysql-mysql 800G 713G 88G 90% /var/lib/mysql /dev/mapper/vgmysql-mysql_tmp 100G 33M 100G 1% /var/tmp/mysql /dev/mapper/vgmysql-mysql_snapshot 800G 712G 89G 89% /var/cache/mylvmbackup/mnt/backup /dev/mapper/vgroot-mysql_backup 805G 33M 805G 1% /var/cache/mylvmbackup/backup machine2:/var/lib/mysql 900G 864G 36G 97% /mnt/machine2
So after rsync the total size of data increases by 150Gb. On comparing sizes of each individual files and file counts, all are same. Sizes were checked using
ls -l and
du command. When checked the partition size on machine2, the following is the output, confirming that disk usage has increased:
On Machine2: /dev/mapper/vgmysql-mysql_tmp 100G 33M 100G 1% /var/tmp/mysql /dev/mapper/vgmysql-mysql 900G 864G 36G 97% /var/lib/mysql
Deleted the entire data on machine2, and re-did the rsync, and again the same result. Now, in all their are 4 databases that MySQL is holding, lets call then database1, database2 .... and database4. Each database has its own directory in /var/lib/mysql.
As mentioned earlier, database1 has the biggest size, or around 656Gb. When check the size of database1 directory in /var/lib/mysql on machine2, its around 799G. Rest all directories and files have same size. Checked each file (ibd and frm) and compared them to files on machine1, and each have same size. No extra hidden file.
So deleted all data again, destroyed the Logical Volume (/dev/mapper/vgmysql-mysql) and recreated them. Did rsync again and got same results, disk usage increasing by 150Gb.
Checked for file system (XFS) parameters on both machines, all are same. Used ncdu command, and difference is clear:
Total disk usage: 864.3GiB Apparent size: 713.3GiB Items: 1500
What is causing the disk usage to increase so much? What am I missing here?