Preparing for Application Consistent backups
TrilioVault for RHV does provide the capabilties to take application consistent backups by utilizing the Qemu-Guest-Agent.
The Qemu-Guest-Agent is a component of the qemu hypervisor, which is used by RHV. RHV automatically builds all VMs to be prepared to use the Qemu-Guest-Agent.
The Qemu-Guest-Agent provides many capabilities, including the possibility to freeze and thaw Virtual Machines Filesystems.
The Qemu-Guest-Agent is not developed or maintained by Trilio. Trilio does leverage standard capabilities of the Qemu-Guest-Agent to send freeze and thaw commands to the protected VMS during a backup process.
The Qemu-Guest-Agent needs to be installed inside the VM.
The Qemu-Guest-Agent requires a special SCSI interface in the VM definition.
This interface is automatically created by RHV upon spinning up the Virtual Machine.
The installation process depends on the Guest Operating System.
yum install qemu-guest-agent
systemctl start qemu-guest-agent
apt-get install qemu-guest-agent
systenctk start qemu-guest-agent
Windows Guests require the installation of the VirtIO drivers and tools.
These are provided by Red Hat in a prepared ISO-file.
For RHV 4.3 please follow this documentation: RHV 4.3 Windows Guest Agents
For RHV 4.4 please follow this documentation: RHV 4.4 Windows Guest Agents
The Qemu-Guest-Agent is calling the fsfreeze-hook.sh script either with the freeze or the thaw argument depending on the current operation.
The fsfreeze-hook.sh script is a normal shell script.
It is typically used to do all necessary steps to get an application into a consistent state for the freeze or to undo all freeze operations upon the thaw.
The fs-freeze-hook.sh script default path is:
/etc/qemu/fsfreeze-hook
The fsfreeze-hook.sh script does not require a special content.
It is recommended to provide a case identifier for the freeze and thaw argument.
This can be achieved for example by the following bash code:
#!/bin/bash
case "$1" in
freeze)
#Commands for freeze
;;
thaw)
#Commands for thaw
;;
*)
echo $"Neither freeze nor thaw provided"
exit 1
;;
esac
This example flushes the MySQL tables to the disks and keeps a read lock to prevent further write access until the thaw has been done.
#!/bin/sh
MYSQL="/usr/bin/mysql"
MYSQL_OPTS="-uroot" #"-prootpassword"
FIFO=/var/run/mysql-flush.fifo
# Check mysql is installed and the server running
[ -x "$MYSQL" ] && "$MYSQL" $MYSQL_OPTS < /dev/null || exit 0
flush_and_wait() {
printf "FLUSH TABLES WITH READ LOCK \\G\n"
trap 'printf "$(date): $0 is killed\n">&2' HUP INT QUIT ALRM TERM
read < $FIFO
printf "UNLOCK TABLES \\G\n"
rm -f $FIFO
}
case "$1" in
freeze)
mkfifo $FIFO || exit 1
flush_and_wait | "$MYSQL" $MYSQL_OPTS &
# wait until every block is flushed
while [ "$(echo 'SHOW STATUS LIKE "Key_blocks_not_flushed"' |\
"$MYSQL" $MYSQL_OPTS | tail -1 | cut -f 2)" -gt 0 ]; do
sleep 1
done
# for InnoDB, wait until every log is flushed
INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
[ $? -ne 0 ] && exit 2
trap "rm -f $INNODB_STATUS; exit 1" HUP INT QUIT ALRM TERM
while :; do
printf "SHOW ENGINE INNODB STATUS \\G" |\
"$MYSQL" $MYSQL_OPTS > $INNODB_STATUS
LOG_CURRENT=$(grep 'Log sequence number' $INNODB_STATUS |\
tr -s ' ' | cut -d' ' -f4)
LOG_FLUSHED=$(grep 'Log flushed up to' $INNODB_STATUS |\
tr -s ' ' | cut -d' ' -f5)
[ "$LOG_CURRENT" = "$LOG_FLUSHED" ] && break
sleep 1
done
rm -f $INNODB_STATUS
;;
thaw)
[ ! -p $FIFO ] && exit 1
echo > $FIFO
;;
*)
echo $"Neither freeze nor thaw provided"
exit 1
;;
esac
Last modified 1yr ago