HP StorageWorks TL895 Adding the TL895 to the Enterprise Backup Solution - Page 30

Lights Out Tests, Calculating Tape Retention, Definition, Procedure

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30 Adding TL895 Libraries to the Compaq Enterprise Backup Storage System Lights Out Tests Lights out tests were designed to consider factors that would affect backup rates when automated tape libraries are connected to the EBS. Tape retention policies determined the number of tapes needed to maintain several sets of backups that can be overwritten after the retention period has expired. Full, Incremental, and Differential backups were analyzed to find factors that would affect performance when large quantities of data were processed. Calculating Tape Retention How you store the backup data on tape and how long you keep the tapes before they are erased greatly impacts the total number of tapes needed to maintain the desired backup schedule. Follow the procedure below to determine the amount of storage you will need. Definition There are three basic types of tape rotation within each backup cycle. Each method offers advantages and disadvantages in cartridge use and restore time. s (F) Full Backups Only--All data is backed up every time a backup is conducted. s (I) Full/Incremental Backups--Each backup cycle will include one full backup and multiple incremental backups. Incremental backups back up all data that has changed since the last backup of any type. s (D) Full/Differential Backups--Each backup cycle will include one full backup and multiple differential backups. Differential backups back up all the data that has changed since the last full backup. Procedure 1. Calculate data sets. Determine the number of full, incremental, and/or differential data sets to be retained. 2. Assign percentages to each backup set for a given number of days. For example:  Full (F) = 100%  Incremental (I) = 20%*  Differential (D) = 20%* *NOTE: Actual Incremental and Differential percentages vary for every backup set, based on the actual amount of data changed. 3. Total the percentages. 4. Calculate total storage needed: Total Percentage * Data Set (in GB) = Total Storage Needed (in GB) 5. Calculate storage capacity of each tape:

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30
Adding TL895 Libraries to the Compaq Enterprise Backup Storage System
Lights Out Tests
Lights out tests were designed to consider factors that would affect backup rates when
automated tape libraries are connected to the EBS. Tape retention policies determined the
number of tapes needed to maintain several sets of backups that can be overwritten after the
retention period has expired. Full, Incremental, and Differential backups were analyzed to find
factors that would affect performance when large quantities of data were processed.
Calculating Tape Retention
How you store the backup data on tape and how long you keep the tapes before they are erased
greatly impacts the total number of tapes needed to maintain the desired backup schedule.
Follow the procedure below to determine the amount of storage you will need.
Definition
There are three basic types of tape rotation within each backup cycle. Each method offers
advantages and disadvantages in cartridge use and restore time.
■
(F) Full Backups Only--
All data is backed up every time a backup is conducted.
■
(I) Full/Incremental Backups--
Each backup cycle will include one full backup and
multiple incremental backups. Incremental backups back up all data that has changed
since the last backup of any type.
■
(D) Full/Differential Backups--
Each backup cycle will include one full backup and
multiple differential backups. Differential backups back up all the data that has changed
since the last full backup.
Procedure
1.
Calculate data sets.
Determine the number of full, incremental, and/or differential data
sets to be retained.
2.
Assign percentages
to each backup set for a given number of days. For example:
±
Full (F) = 100%
±
Incremental (I) = 20%*
±
Differential (D) = 20%*
*NOTE:
Actual Incremental and Differential percentages vary for every backup set, based on the
actual amount of data changed.
3.
Total
the percentages.
4.
Calculate total storage
needed:
Total Percentage * Data Set (in GB) = Total Storage Needed (in GB)
5.
Calculate storage capacity
of each tape:
35 GB * Compression Rate = Tape Capacity