The Access 3340 Appliance can scale up to 2.8 PB of usable capacity. Although the FlashArray volume snapshots are compressed, to create portable and efficient snapshot, FlashArray has about a 5% overhead. For this simplistic sizing exercise, capacity is evaluated with an initial source data of 100 TB in size, a known data compression ratio of 2:1, retention of 30 days, and daily change rate of 5%. The sample capacity required for 30 days would be as follows:
Capacity Needed = ((Data Size + (Retention * Change Rate * Data Size) * Compression Rate) + (Data Size * 5%)
= ((100 TB + (30 days * 0.05 per day * 100 TB)) * 0.5 compression) + (100 TB * 0.05)
= 125 TB + 5 TB
= 130 TB
In addition, when old snapshots expire, the data blocks from these snapshots are not converted into free space immediately, so it conceivable that at some point in time the space consumed by the above snapshots will approach the following:
Capacity Needed = 130 TB / 70%
= 186 TB
Therefore, capacity on Access Appliance should be calculated to include room for the above overhead.