Arkeia Software

How to Choose

Many factors impact your choice of data protection strategy. Protection against natural disaster or theft, and most regulatory frameworks, requires off-site storage of backups. Arkeia supports all three of the most common strategies for off-site storage. These are:

  • Backup sets on tape media transported by truck (or sneaker-net)
  • Backups direct to cloud storage
  • Backup sets transferred over the WAN to cloud storage

Strategies for Off-site Storage

The first strategy, "to-tape", is practiced in two variations: backups to tape and backups-to-disk-to-tape (D2D2T). If backups to disk are maintained on a LAN-resident backup server, restores are fast except when data must be retrieved from the remote site. If backups are made directly to tape, the media cost of backups is lower.

Cloud-Disk-Tape Tradeoffs

The pros and cons of these three strategies are summarized in the table to the left. Backups to and restores from WAN-connected media are simple, but unacceptably slow for all but the smallest data volumes.

For most enterprises, the best strategies start with backups to media on the LAN.

Backups that are direct-to-tape offer slow restores but impose minimum media costs. Backups direct-to-disk are usually followed by replication of all data to tape or to cloud storage, but often include retention of some data on the local disk because typically 90% of restores are performed within a month of backup.

For offsite storage to both tape and cloud, Arkeia recommends that data are encrypted before they leave your premises. Encryption guarantees data privacy if the media are lost, stolen, or hacked. The question then becomes: How to choose between tape and disks-in-the-cloud for off-site storage.

Tape vs. Cloud

For storage in the cloud, network bandwidth limits options, imposing either long backup windows, high bandwidth costs, local backup staging with replication, or some combination. Block-grain deduplication can greatly reduce network costs. Learn more about Arkeia’s industry-leading Progressive Deduplication™ technology.

Offsite Storage Costs

For small volumes of data, off-site storage on disks in the cloud may be less expensive than off-site storage on tape due to the costs of tape handling procedures. For large data volumes, especially when access is infrequent and retention periods are long, tape is the undisputed champion for off-site storage.

The graph at left summarizes the cost profiles of these two off-site storage strategies. Off-site tape storage costs less per TB--but imposes fixed costs for personnel and daily tape transport. Off-site cloud storage costs more per TB--but start-up costs are minimal. The data volume at which the costs of the alternative solutions are equal is rising over time, and both lines are flattening over time.

Cost Impact

If cost is your most important factor, the cloud can be an attractive option at small data volumes. Tape is the more attractive option at large data volumes. The exact slopes of the two curves depend on your choice of providers and technologies.

Off-Site Tape Storage Costs Cloud Storage Costs
  • Tape drive / library cost
  • Media cost
  • Media transport costs
  • Personnel cost
  • Network bandwidth cost
  • Cloud storage (disk volume) cost

Volume Impact

Data volume imposes another limit on cloud storage. Assuming that all backups are staged to LAN-resident disk, cloud backups separate into two regimes.

In the first regime, a full backup can be sent over the WAN in reasonable time (e.g. several days) and incremental backups in several hours. For example, a dedicated 10Mbps link can transfer 100GB per day. A data volume of 500GB would require 5 days to complete the initial backup. An alternative data protection process would be required until the initial full backup and five days of incremental backups are replicated to the cloud.

In the second regime, the initial full backup requires transport of media (e.g. tapes or ruggedized NAS) to the NOC in the cloud, but daily incremental backups can be managed over the WAN. If 1% of data changes every day, then a 10Mbps link can only protect 10TB of data. If data change rates exceed 1% or bandwidth cannot be dedicated to data protection, this upper limit drops.

If the volume of data in any day’s (incremental) backup cannot be transported to the cloud in the 24-hour period following the close of the backup window, cloud backup may not be practical. Contact Arkeia to learn more about the successful strategies employed by our customers.