Best practice in using removable disk cartridges (RDX) as a storage device with Veritas System Recovery

Problem

Best practice in using removable disk cartridges (RDX) as a storage device with Veritas System Recovery (VSR).  These drives are also known as RDX 1000 and RD1000.

Cause

VSR atempts to automatically remove older recovery point images to stay within the retention limit specified within the backup job setting:  "Limit the number of recovery point sets saved for this backup."  A recovery point set consists of a Base (aka Full) backup (.v2i file extension) plus all Incrementals (.iv2i file extension) occurring after it until the next Base backup runs.

1.  Depending upon the type of backup job being used, VSR, by design, needs to have enough room on the RDX cartridge to create one additional base or Independant backup beyond the value of the retention period. Once this threshold has been met, VSR will delete the oldest recovery point set.  VSR determines the earlist recovery point image based upon information stored in the backup history files (i.e. *.PQH files).

Example: If the default value of three is kept for the backup job setting, "Limit the number of recovery point sets saved for this backup," then there needs to be enough space on the RDX cartridge for a fourth set. If the history file becomes corrupt or has been cleared/deleted before reaching this fourth set, the recovery points stored on the RDX cartridge(s), created prior to the current history file was made will become 'Orphaned' and will need to be manually removed from the cartridge(s).

2. VSR, by design, executes the command to remove older recovery point sets shortly after the successful creation of this, 'one additional,' base image.  If the earliest recovery point set (i.e The oldest baseline and its incremental updates) scheduled to be removed is not on the RDX cartridge currently inserted, VSR will delete that recvoery point set after the RDX cartridge containing them is reinserted and a new base backup is completed on the cartridge.

NOTE: This applies to System Recovery 2013 R2 and newer.  With System Recovery 2013 and earlier, if the cartridge containing the oldest recovery point set is not currently available when the recovery point set limit is exceeded, the old recovery point set will be orphaned on the cartridge and will not be deleted at a later time when that cartridge is reinserted into the RDX drive. Manual intervention is required by the user to delete the oprhaned recovery point sets.

3.  A new base backup is always created the first time a backup runs after a different RDX cartridge is inserted, even if an incremental backup was originally scheduled.

Solution

There are two possible approaches to using RDX cartridges with VSR:

• Single job approach
• Multiple job approach
  

Single job approach

1.   The number of recovery sets to retain should be a multiple of the number of cartridges used in rotation
eg. If available cartridges = 2, the number of recovery point sets to retain could be 2, 4, 6 etc, depending upon how many recovery point sets can be accommodated on a single cartridge.  Keep in mind there needs to be room for the number of recovery point sets specified plus one additional base backup since VSR does not delete the oldest backup once the recovery point set limit is reached until a new base backup is created. 

2.   Create only one backup job (with recovery point set) that will take only incremental backups. Base backups will be taken as soon as the cartridge is rotated.  Backup job schedule should be configured to create base backups as infrequently as possible (i.e. Yearly). 

3.   The path specified for the backup destination should exist on each RDX cartridge

Usage scenarios:

Scenario 1:
One backup per day, 1 cartridge for Monday through Thursday and another one for Friday through Sunday.  
Limit the number of recovery point sets saved for this backup = 2 
Number of cartridges = 2
Each cartridge needs room for 2 base backups plus all incrementals associated with oldest base backup.

Scenario 2:
One base and one incremental per day, rotate cartridge every weekday. 
No backups Saturday or Sunday
Limit the number of recovery point sets saved for this backup = 4
Number of cartridges = 2
Each cartridge needs room for 3 base backups plus all incrementals associated with oldest 2 base backups.

Multiple job approach:

• Can be used if only base (Full) backups are desired.  Recovery point set jobs cannot be created in this manner as each source drive can only have one recovery point set job defined for it.
• Use the RDX drive as a primary removable / swappable storage device if the capacity of all cartridges involved in the rotation cycle can contain two or more full backups.
• Do not reuse RDX cartridge(s) for a new client's cartridge rotation cycle until all the cartridge(s) has been reformatted.
• Create a seperate independant backup job (not a recovery point set) per each RDX cartridge to be used in the client's rotation cycle. By doing this, each backup job will have its own history file per drive selected to maintain retention.

Example: If a VSR client has three RDX cartridges in its rotation cycle, with each cartridge having the capacity that can contain three full backup images, the retention period would then be set to two on each job providing a one week of recovery window as shown below: 

 Expected image and retention site schedule:

Applies To

Windows based client systems.