Determining Catalog Space Requirements

NetBackup requires disk space to store its error logs and information about the files it backs up. The maximum amount of disk space that NetBackup requires at any given time varies according to the following factors:

• Number of files that you are backing up
• Frequency of full and incremental backups
• Number of user backups and archives
• Retention period of backups
• Average length of full pathname of files
• File information (such as owner permissions)
• Average amount of error log information existing at any given time
• Whether you have enabled the database compression option.

  To estimate the disk space required for a catalog backup

1. Estimate the maximum number of files that each schedule for each policy backs up during a single backup of all its clients.

   Example Reference Table for Catalog Requirements shows that a full backup for policy S1 includes 64,000 files.

2. Determine the frequency and retention period of the full and incremental backups for each policy.
3. Use the information from steps 1 and 2 above to calculate the maximum number of files that exist at any given time.

   For example:

   Assume you schedule full backups every seven days with a retention period of four weeks and differential incremental backups daily with a retention period of one week. The number of file paths you must allow space for is four times the number of files in a full backup plus one week's worth of incrementals.

   The following formula expresses the maximum number of files that can exist at any given time for each type of backup (daily, weekly, and so on):

   Files per Backup x Backups per Retention Period = Max Files

   For example:

   If a daily differential incremental schedule backs up 1200 files for all its clients and the retention period is seven days, the maximum number of files resulting from these incrementals that can exist at one time are:

   1200 x 7 days = 8400

   If a weekly full backup schedule backs up 3000 files for all its clients and the retention period is four weeks, the maximum number of files due to weekly-full backups that can exist at one time are:

   3000 x 4 weeks = 12,000

   Obtain the total for a server by adding the maximum files for all the schedules together. The maximum number of files that can exist at one time due to the above two schedules is the sum of the two totals, which is 20,400.

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     Note    For policies that collect true-image-restore information, an incremental backup collects catalog information on all files (as if it were a full backup). This changes the above calculation for the incremental from 1200 x 7 = 8400 to 3000 x 7 = 21,000. After adding 12,000 for the fulls, the total for the two schedules is 33,000 rather than 20,400.

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4. Obtain the number of bytes by multiplying the number of files by the average length of the file's full pathnames and file information.

   Determining the space required for binary catalogs:

   If you are unsure of the average length of a file's full pathname, use 100. Using the results from the examples in step 3 yields:

   (8400 x 150) + (12,000 x 150) =3060000 bytes (or about 2988 kilobytes)

   Determining the space required for ASCII catalogs:

   If you are unsure of the average length of a file's full pathname, use 150. (Averages from 100 to 150 are common.) Using the results from the examples in step 3 yields:

   (8400 x 150) + (12,000 x 150) = 2988 kilobytes (1024 bytes in a kilobyte)

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     Note    If you have ASCII catalogs and use catalog indexing, multiply the number in step 4 by 1.5%. For information on catalog indexing, see Reduce Restore Times by Indexing the Image Catalog.

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5. Add 10 to 15 megabytes to the total calculated in step 4. This is the average space for the error logs. Increase the value if you anticipate problems.
6. Allocate space so all this data remains in a single partition.