Sizing journal volumes

Journals volumes should be sized to meet all possible data scenarios, based on your business requirements. If the amount of data exceeds capacity, performance problems and suspensions result.

Hitachi recommends a capacity of 6 GB or more. Journal volumes cannot be registered if capacity is lower than 1.5 GB.

Procedure

  1. Follow the instructions for Measuring write-workload.

  2. Use your system’s peak write-workload and your organization’s RPO to calculate journal size. For example:

    RPO = 2 hours Write-workload = 30 MB/second Calculate write-workload for the RPO. In the example, write-workload over a two-hour period is calculated as follows: 30 MB/second × 60 seconds = 1,800 MB/minute 1,800 MB/minute × 60 minutes = 108,000 MB/hour 108,000 MB/hour × 2 hours = 216,000 MB Basic journal volume size = 216,000 MB (216 GB)

Results

Journal volume capacity and bandwidth size work together. Also, your strategy for protecting your data might allow you to adjust bandwidth or the size of your journal volumes. For details about sizing strategies, see Five sizing strategies .

Next steps

NoteJournal data stored in the master journal volume is not deleted until the data is restored to the secondary volume. Therefore, if the restore journal volume is larger than the master journal volume, the master journal volume first becomes full. If you are planning for disaster recovery, the secondary storage system must be large enough to handle the production workload, and therefore, must be the same size as master journals.