Cisco Headend System Release 2.7 Installation Guide
Appendix D
Storage Requirements
Storage Requirements
46
Determining Growth Factor
A rule of thumb for file growth is to count on 20 percent to 30 percent growth per
year. If you are trying to size backup storage for three years, count on needing
between 175 percent to 225 percent of your initial space by the end of three years.
A rule of thumb for file growth is to count on 20 percent to 30 percent growth per
year. If you are trying to size backup storage for three years, count on needing
between 175 percent to 225 percent of your initial space by the end of three years.
Number of Copies
This is a number that the site will have to determine based upon business needs, but
should never be less than two. Having two copies gives the site a means to ‘fence in’
a maintenance activity with backup pre-maintenance and another immediately post-
maintenance. Other factors to consider are:
This is a number that the site will have to determine based upon business needs, but
should never be less than two. Having two copies gives the site a means to ‘fence in’
a maintenance activity with backup pre-maintenance and another immediately post-
maintenance. Other factors to consider are:
How long an error goes unnoticed and requires a restoration to something other
than the most recent backup
than the most recent backup
Data forensics; more copies allow you to find when a change was made to the
system
system
Summary Example
The total disk space required for backups can be calculated, as follows:
Assumptions
Assumptions
Database backup size = 20 GB
Key files backup size = 6 GB
File systems backup size = 40 GB
Number of database + key file backups = 7 (daily backups)
Number of file system backups = 4 (weekly backups)
Disk space required for database and key files backup for one month:
[(20 GB + 6 GB) * 7 days/week] * 4 weeks/month = 728 GB/month
Disk space required for file systems backup for one month:
Disk space required for file systems backup for one month:
[40 GB * 4 weeks/month] = 160 GB/month
Total disk space required per month for backups:
Total disk space required per month for backups:
728 GB/month + 160 GB/month = 888 GB/month
If the site does not overwrite their backups, the total disk space required for a
month:
If the site does not overwrite their backups, the total disk space required for a
month:
888 GB/month * 12 = 10, 656 GB/year (10.656 TB/year)
However, most sites would want to overwrite their backups or preserve only a