When the amount of data to be backed up becomes large the time to run a total backup, and the tape space it occupies becomes a problem. Instead of making a total backup every time, it is more efficient to have a program of backup jobs which makes a total backup, followed by a number of incremental (or differential) backups, then then at some point start the program again with a fresh total backup.
We wanted to be able to recover Arkeia Sports Centre data: 1. from any of the last 30 days; and
2. as at the end of each of the last 3 months.
We decided on this program of backups:
• Monthly total backup, valid for 4 months. This covers the second require- ment.
Extreme case example:
It is the last day of June, a file from the last day of March is required. The March total backup is still available as its validity period of 4 months has not expired, so the file can be recovered from that backup data set.
• Daily partial backup, of files which have changed since the last monthly backup, valid for 31 days. This covers the first requirement.
Extreme case example:
On 30 June, a file needs to be restored to its state as at 31 May (30 days ago). This file can be restored from the differential backup of 31 May. If it is not in this backup, it because the file has not changed since the previous total backup, which was the monthly total backup for April. In this case, the file will be found in the April total backup data set.
From the end of the second month onwards, we will have in storage a backup data set of 2 total backups and 31 daily partial backups. In the third month, the earliest monthly total backup data set will have passed its validity date, and can be over- written with the data set of a newer backup job.
The data to be backed up is likely to be in files which are currently open in the applications which create them. Before we back them up it is necessary to close the applications and the data files to avoid clashes. But we also need to run our back- ups:
• with as little disturbance as possible to the Sports Centre, and
• without having to be on-site at some inconvenient time.
Not surprisingly, there were no volunteers to come in and start the backup jobs dur- ing the dead hours from midnight to 5 am, so we will make use of two
Arkeia Smart Backup features solve the problem:
• deferred backup, which will allow us to start the backup during the dead hours without being on site;
• command before and command after the backup, which will run script files to stop any applications which have files open in the data to be backed up, and re-start them when the backup job has finished. The scripts are called
stop_sports.bat and start_sports.bat, located on the client computer.
The commands run by Command before and Command after must return a zero error code, otherwise Arkeia Smart Backup will assume the command failed (even if it did not). If the command returns nothing, Arkeia Smart Backup assumes it failed, and may not run the backup job.
Total deferred backup configuration
We clicked on then
to open the
Backup configuration wizard, clicked on Deferred
backup, then to continue the configuration.
In this screen, we:
1. entered a name for the backup configuration:
ASC_total;
2. chose Total backup as the backup type. 3. Set the validity period
for 2 months;
4. set the start date and
time for just after mid- night on June 01; 5. in Advanced options,
entered the path and command names of the scripts which stop and start the processes acting on the client data to be backed up, to avoid clashes; and 6. checked the Execute
command if backup fails box, to ensure
that everything is set back to normal, even if the backup fails.
We clicked on Next to continue the backup job configuration by selecting the data to be backed up by this configuration, as we did in Step 2: on page 30 above.
This is the configuration for a total backup, deferred to start at a future time. Here are the requirements for this backup job to run successfully.
• The client computer must be online at midnight on May 31.
• The Arkeia backup server computer must be online at midnight on May 31.
• A tape cartridge must be in the tape drive at the start time.
• This tape cartridge must:
- not have any other Arkeia backup data on it, if this is the first time it is used for this backup job;
- belong to this backup configuration, if it is not the first time the tape has been used for this configuration; and
- have enough space available to hold the backup data set.1
• The command designated in the Command before field must exit normally, without error.
Incremental interactive backup configuration
Interactive incremental backups are based on a backup data set from some previous backup job run in Arkeia Smart Backup.
Incremental backup jobs are usually smaller and quicker than total backup jobs1, so take less time. We will make the daily backup job an interactive backup, and start it manually every day, warning users that the system will be off line for backup for a few minutes.
An incremental backup configuration must be based on another backup. If no other backup exists, you cannot create an incremental backup configuration.
Because we need to base the incremental backup configuration on the total backup, we had to wait until the total backup job ran until we could create the incremental backup configuration.
We clicked on then to open the Backup configuration wizard, and clicked on Interactive backup then on Next to continue.
In this screen, we:
1. Entered a name for the backup configuration:
ASC_incremental. 2. Chose Incremental
backup as the backup type.
3. Chose the last total backup as the base for this incremental backup.
4. Set the validity period for 31 days.
5. In Advanced options, entered the path and command names of the scripts which stop and start the processes acting on the client data to be backed up, to avoid clashes.
6. Checked the Execute command if backup fails box, to ensure that every- thing is set back to normal, even if the backup fails.
1. This is true except if all, or the majority of the data to be backed up changes between incremental backup jobs.
We clicked on Next to continue the backup configuration by selecting the data to be backed up by this configuration, then clicked on Save. Arkeia Smart Backup asked if we wanted to run this backup now, and we clicked Yes.
Arkeia Smart Backup asked for the tape for this backup configuration. Since this was the first time it was run, a blank tape was labelled ASC_incremental TAPE 1 then inserted, the message cleared, and the backup proceeded.
From this point on, we were able to run the incremental backup by: 1. ensuring the client computer is on line,
2. inserting the correct tape,
3. clicking on to open the Backups management screen,
4. highlighting the the backup config- uration in the list, then
5. clicking on to launch the backup.
This is an interactive partial backup job, based on the total backup dated June 1, 2006. Every time we click Start, the backup will copy all the files which have changed since June 1, 2006 into the backup data set. At the start of each new month, we must edit the configuration and change Based on to the latest total backup.
Although we chose incremental in the configuration, it is a differential backup if we run it as described above because it is always based on a total backup. To make it a true incremental backup, we would have to edit the configuration each day and changed Based on to the previous day’s incremental backup job.
In a periodic backup job this is automated, Arkeia Smart Backup always bases a periodic incremental backup on the data set of the last backup job run with that configuration.
Next
The two backup configurations we have just created form a program of regular backups. To repeat the backups, we must remember to:
• change the date of the monthly total deferred backup to start it each month,
• change the Based on field of the incremental backup each month to the new monthly total backup, and
• manually start the daily incremental interactive backup each day.
A periodic backup program would start the backup jobs for us and continue run- ning the jobs each month and day, but with our current setup of one tape drive, it would be necessary to remember to insert the correct tapes before the backup jobs