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Which three components are used to calculate the journal size for a Zerto data protection solution?
Zerto journal size is based on the retained history duration, the average write throughput generated by all protected VM volumes, and the effective compression factor for the journaled changes. Continuous Data Protection records write changes and checkpoints so applications can be returned to an earlier point within the configured history window. In simplified form, journal space equals history in seconds multiplied by average data write rate and the applicable compression factor. For one hour of history at 10 MB/s and a 0.5 compression factor, the calculation is 3,600 x 10 x 0.5 = 18,000 MB, approximately 18 GB before operating margins. Network throughput is not interchangeable with the underlying VM-volume write rate, and deduplication ratio is not one of the three specified terms in this formula. Architects should separately consider change-rate peaks, growth, replication lag and additional free capacity. Correct journal planning must be based on actual application write characteristics because insufficient journal resources can shorten the recovery history available during an incident.
Study Guide Reference: HPE Zerto journal sizing: duration, VM write throughput and compression.
Official reference(s): HPE Storage Solutions course
Batch 6 | Questions 51--60