Knowledgebase: Backup Strategies
Backup to disk, best practice for small business
Posted by Sven Koester, Last modified by Sven Koester on 19 October 2017 15:28

This article attempts to describe a best practice for a backup to disk in a small business environment to save data to an external hard disk in a separate case, connected e.g. via USB or FireWire and supported by the operating system.

A note in advance: there does not really exist one  best practice. There are multiple ways to set up a backup to disk, each one fitting to another set of requirements. Because of that, this article will show some often used setups. Please pick the best one with regard to your requirements.

Use synchronize for backup
This method is recommended in case the external disk is not considerably bigger than the data to back up and in case the recovery time must be minimized.
The use of Synchronize as backup to disk is described in more detail in a separate article.
It requires a PresSTORE Synchronize license.

Use backup to write onto a virtual jukebox created on one or multiple external hard disks
The methods described below explain multiple variants that create a backup to disk using a virtual jukebox created on the disk.
These require a PresSTORE Backup Workgroup license.

Preparations
PresSTORE simulates a virtual jukebox with virtual media (tapes) on the disk, where an external disk can be seen as a cartridge in the jukebox where the virtual disks reside. During setup in the jukebox manager in the PresSTORE web interface, the jukebox must be configured by defining the number of slots the jukebox has and the size of these slots. When using the jukebox, these parameters define the size of the single virtual tapes and the number of virtual tape files on the disk. See the variants described below for recommendations regarding the size and the number of slots.
Please make sure that the required space (size times number of slots) fits onto the external disk. Please note further that PresSTORE generates so called sparse files, that means that virtual volumes of e.g. 100 GB require only a few MB disk space as long as they do not hold data.

Care must be taken when setting up a virtual jukebox for use with multiple external disks: make sure that the disks are mounted always to the same mount point when connected to the host and have the same path to the jukebox directory. On a Mac, the same mount point can be ensured by assigning the same name to both disks, Mac OS X will then mount the volumes at the same directory. On Windows, the next free drive letter is used automatically, but there are tools available in the internet that promise to assign drive letters with a fix assignment e.g. by USB port.
Note that PresSTORE's virtual jukebox accesses files on a configured path, PresSTORE does not ensure that the path is located on an external disk. If the required disk is not present, the data may end up being written on the underlying mount point.

To create the virtual tapes, follow these steps:

  • Connect the first external disk
  • Enter the Jukebox manager and call Add new Jukebox, then select the virtual jukebox.
  • Refer to the sections below for number of slots and size of the slots.
  • Call from the menu Label Volumes, this step creates the virtual tape files.
  • Disconnect the first drive and connect the second one. In case you created a directory for the data on the first drive, please create the same directory on the second dive.
  • Call again the Label Volumes method to create the virtual tape files on the second drive.

Use two disks weekly alternating with a strict backup plan, 2 cycles
This method is recommended in case the external disk has at least one and a half times the capacity of the backup data and the machine(s) to backup are available during known time periods. It requires two disks, the disks are exchanged weekly.
The idea is to write a full backup on the weekend and subsequent incremental backups on weekdays to one disk, then exchange the disks and do the same over the next week

Create the following backup plan:

  • Saturday: Full backup
  • Sunday: Skip (so you have twice the time for the full backup)
  • Monday to Friday: Incremental Backup

In the backup plan, the following options must be set:
 Backup Plan > Additional Options > Backup cycles to keep: 1
In this setup, it does not matter how many slots (virtual tapes) are created on the jukebox.

This method can be used in the same way when performing a daily full backup, with daily disk exchange.

Use two disks alternating with a strict backup plan, 4 cycles
This method is recommended in case the external disk is huge compared to the data to save and the machine(s) to backup are available during known time periods. It requires two disks, the disks are exchanged weekly.
The idea is to write a full backup on the weekend and subsequent incremental backups on weekdays to one disk, than exchange the disks and do the same over the next week
In opposite to the above example, this method saves additional backup cycles on the disks.

Create the following backup plan:

  • Saturday: Full backup
  • Sunday: Skip (so you have twice the time for the full backup)
  • Monday to Friday: Incremental Backup

In the backup plan, the following options must be set:
 Backup Plan > Additional Options > Backup cycles to keep: 4
Backup Plan > Additional Options > Volume Use: Use new media
Media Pool > Additional Option > Recycle policy: When volumes are needed

When creating the jukebox slots, make sure that the full backup plus all increments over the week fits to one half of the virtual tapes of one disk.
Example:
Assuming your backup has 100 GB and you expect incremental data of 10 GB * 5 weekdays in one cycle, so one backup cycle requires 150 GB.
The external disk for backup has 500 GB, two cycles shall fit onto one disk.
So you could create

  • 2 slots with 250 GB each
  • 10 slots with 50 GB each
  • or another even number of slots between.

The smaller slots allow an easier change of the strategy because PresSTORE must recycle a tape in whole, it cannot recycle parts of a tape.
See below.


Use two disks alternating with a liberal backup plan, variable cycles

This method is recommended in case
- either the machine(s) to backup are only available from time to time, or
- the backup is often started manually by other reasons

When using multiple backup plans, maybe with different numbers of cycles and maybe with a non regular start time (e.g. when backing up laptops that are only rarely available, then the amount of data of one week (or day) may significantly differ from another. Because of that, a dynamic and flexible solution is required. PresSTORE is designed to operate on tapes and recycles tapes in whole. So a small slot size (or size of the virtual tape) is recommended here in order to fill the tapes faster and recycle tapes in smaller portions.

Create the backup plan according to your needs, you may want to disable the automatic start.
In the backup plan, the following options must be set:
  
Backup Plan > Additional Options > Volume Use: Append to media
Media Pool > Additional Option > Recycle policy: When volumes are needed


 We suggest the create a high number of slots, e.g. 10 or 12 slots. Please calculate the size by dividing the size of the disk by the number of slots.

 

 

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