Size edge storage from write workload and recovery needs

Bottom line: a card that nominally holds the required number of days may still be unsuitable for the write rate, service interval, environment, or recovery process. Edge storage should be sized as a recording system, not purchased by capacity alone.

Source fact: long retention and high frame rates can require offload

Axis’s Surveillance cards for edge storage discusses storage cards designed for surveillance write workloads and the use of edge storage for decentralized or failover recording. It notes that longer retention or higher frame-rate needs may require recordings to be offloaded to server or cloud storage.

The operational consequence is a two-phase design problem. The card must sustain production writes for the required interval, and the system must later transfer or reconcile accumulated video quickly enough while new video continues to arrive.

Source boundary and applicability

The paper describes Axis surveillance cards and vendor scenarios; any retention or endurance claim is product-specific. It does not establish that consumer media, every third-party card, or every camera will behave the same way. Usable capacity, codec, scene, event rate, temperature, encryption, filesystem overhead, spare area, and card age affect results.

Applicability questions

What measured write rate occurs in quiet, busy, low-light, and worst-case scenes?

Is recording continuous, event-driven, failover-only, or a combination?

What outage duration and technician response time must the card cover?

How much reserve is needed for variability, card aging, and offload delay?

Can the network and recorder ingest backlog while also recording current streams?

DSE recommendation: calculate and rehearse both phases

The following steps are DSE recommendations based on the cited source.

Measure actual bytes written over representative production intervals for each camera class. Calculate required usable capacity from the high-case rate, outage or retention target, and an approved reserve. Compare the resulting write workload and environment with the exact card and camera documentation. Include replacement lead time and an explicit point at which loss of card capacity becomes an incident.

Stage the longest credible recording interval in a lab or maintenance window, then restore connectivity. Measure backlog transfer time, network and recorder load, searchability, and whether new recordings remain continuous during reconciliation. Do not use unverified marketing averages as the only input.

Also repeat a shorter outage after the card has accumulated representative use. This checks that the recovery design does not depend on a factory-new medium or an empty recorder queue.

Verification and evidence

Retain the stream measurements, calculation, media approval, camera/card inventory, environmental assumptions, test timestamps, oldest-footage checks, transfer-duration data, retrieved clips, health metrics, and replacement plan. Recalculate after resolution, frame rate, codec, analytics, scene, or retention changes.

Official references

Surveillance cards for edge storage – Axis Communications