Dell PowerFlex Appliance with PowerFlex 3.x Administration Guide

Adding journal capacity percentage

The journal is a component of the SDR. It stores the data at the source before it is sent to the destination. At the destination, the journal stores the data before it is applied to the destination volumes. At the source, application I/Os are sent by the SDC to the SDR. The SDR packages I/Os in bundles and sends them to the target journal. Once the I/Os are sent to the destination journal, they are cleared from the source journal. Once the I/Os are applied to the target volumes, they are cleared from the destination journal.

Journal capacity is defined as a percentage of the total storage capacity (usable capacity) in the storage pool and must equal at least 28 GB per SDR. The journal capacity is allocated from every pool where there are replicated volumes. The capacity allocated from each pool is at least 5% of the usable capacity of the replicated volumes. The total allocated journal capacity from all the pools in the protection domain must be at least equal to number of SDRs x 28 GB.

Example of PowerFlex system with 1 PD and 1 SP: If you have four SDRs in your protection domain and SP with 36 TB usable capacity of replicated volume, then the minimum journal capacity should be maximum (5% of 36 TB, (4x28 GB) which is maximum (1.8 TB, 112 GB) = 1.8 TB.