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High Availability  / Components  / Application Availability  / Data Protection  / Backup  /  Extended backup technologies

Extended backup solutions

Continuous Data Protection (CDP)

Disadvantage of classical backup strategies in form of daily or hourly backups is the huge RPO. In this case RPO is as huge as Backup Window to avoid interleave of backup. Aim of CDP solutions are minimizing RPO.

CDP technology is a simple backup technology where only data changes are continuos monitored and recorded. Each data modification is recorded and matched in time. By calling the origin data and stored modifications it is possible to reproduce data state of any time.

CDP recording can be block or file oriented and consist of relevant selection criteria to reproduce data from the mass of data. Thereby RPO can be reduced nearly null.

It is differed between In-Band and Out-of-Band solutions:

  • In-Band

These solutions are based on components (SAN or NAS ) that are interconnected during data flow. Thereby agents are not used any longer and platform unattachment is achieved. RTO can be reduced nearly null , because supply of SAN or NAS areas is possible during data consolidation run in backround. Disadvantage of In-Band solution is the dependence of SAN/NAS connectivity for all CDP protected systems. By using iSCSI (SCSI via TCP/IP) the problem can be adressed and costs could be minimized.

  • Out-of-Band

These solutions are based on agents or drivers that are installed on the system. This involves that possible system platforms are limited by the availability of agents. An advantage is implementation without SAN or NAS. RTO minimization is not possible at all, because restore corresponds typical backup/restore concepts.

  • adressed classification numbers of backup:
    • minimization of RTO (In-Band solutions nearly null)
    • minimization of RPO (nearly null)
    • minimization of Backup Impact
    • elimination of Backup Window
    • possibility of consistent backup

Snapshots

Snapshots adress two backup problems: consitens and Backup Impact. Snapshots are based on Copy-On-Write (COW) technologies and freeze the entire filesystem for about one to two seconds and create a copy of data structur (meta data). Some manufacturer also name the process as Point-in-Time copy. To create snapshots there are two possibilities: Either copyingthe whole structure of the file system or recording data of the storage blocks on RAW partition.

During creation a snapshot no data blocks are copied. Only a copy of management information is created. Is writing process put into operation to snapshot or original data the changed data block is copied into namespace of snapshot. Than the writing process starts. Reading occurs only inside namespace. Data blocks that are not changed are read from namespace. Thats why snapshots use just that   storage volume that is needed for changes during lifetime of snapshots.

A consistent backup is possible, because snapshots record data to a defined time and changes do not depend on original data. Changes at original data are not possible. Therby snaphots eliminate Backup Impact. Logical Volume Manager for Linus supports writabel snapshots on logical volume level.

  • adressed classification number of backups:
    • minimization of Backup Impact
    • possibility of consistent backup

Virtual Tape Libraries (VTL)

Virtual Tape Libraries provide virtual tape drives for backup. They typically base on disk-based systems (random access) that can be adressed via tape interfaces (sequential access). Thereby it is possible to access tapes and minimize restore and Backup Window without changing backup strategy or software.

VTL is a fast tape drive.

  • adressed classification number of backup:
    • minimization of RTO
    • minimization of Backup Window

Backup to Disk

Similar to VTL RTO and Backup Window should be minimized by Backup to Disk solutions. This is realized by bringing a disk based system infront of the tapa drive. Backups are written on the fast disk system first. Than data are written to tapes without Backup Window. The most current version are mirrored on the disk system so access in case of restore is faster.

  • adressed classification numbers of backup:
    • minimization of RTO
    • minimization of Backup Window