Both tape and disk technology have proven their usefulness as storage media for data backups. To determine which technology is the right choice for a backup target in your organization, consider the strengths and weakness of each one.
Tape has long cemented itself as a natural backup tool by providing low-cost storage where performance hasn't been a priority. As the cost of HDDs has decreased, disk has become a worthy backup competitor. Disks have steadily transitioned from predominantly handling primary workloads to operating as backup targets.
Cost, performance and security are a few of the major factors backup admins must consider when evaluating tape vs. disk backup. To a lesser degree, some organizations may take sustainability into account when they choose to invest in their tools, as well as look at how the tool has evolved and may continue to improve over time.
Weighing costs against performance
It's impossible to consider the effectiveness of a storage media as a backup tool without considering costs. Both tape and disk backup technologies present a cost-effective option when compared to higher performance solid-state technology. When compared head-to-head on a per-terabyte basis, however, tape consistently presents the cheapest storage option. This is an especially important when considering the large amounts of data a modern organization needs to back up.
Raw costs alone, however, aren't the only important factor in determining a backup method. Recovery point objective (RPO) and recovery time objective (RTO) quantify the amount of data that may be lost and how quickly data can be restored during an outage. These are crucial metrics that organizations use to calculate the monetary cost of data loss and application downtime.
Disk-based options offer much quicker backups and restores when compared to tape, and disk can help organizations reach their RTO and RPO goals. In the long run, consistent rapid recovery may justify a more expensive disk storage option.
Don't overlook security as a factor
Another key differentiator -- apart from tape's low cost and disk's superior performance -- is the inherently secure nature of offline tape storage. Tape is easily removed and stored offline, a feature commonly used for air-gapped protection against ransomware.
Some disk options can mimic this capability with a logical air gap. Logical air gaps also isolate the storage by removing disk access from host networks. The storage isn't physically removed in the same manner as a traditional air gap, however, leaving the potential for a cyber attacker to find this gap and exploit it.
With ransomware such a large and growing threat, the ability to use a physical air gap is a major benefit of using tape backup.
Sustainability and evolution
In addition to increased security, offline tape storage offers energy savings compared to the constant energy use associated with disk storage. This can save companies money and also help them meet their sustainability goals.
Tape and disk backup continue to develop over time. Disk manufacturers are increasing areal density of drives with technologies such as heat-assisted magnetic recording and microwave-assisted magnetic recording, as well as other technology innovations to create higher capacity drives.
Tape continues to see developments through the latest LTO-8 and LTO-9 generations, including increased capacities and compression, hardware-based encryption and increased data transfer rates. It should be noted that the latest generation LTO tape technology is, and will likely continue to be, limited with backwards compatibility of only one generation. This will require organizations to perform consistent technology refreshes and data migrations to keep up.
Overall, both disk and tape technologies provide strengths and weaknesses for backup storage, and neither is likely to disappear anytime soon.
Many organizations implement tape and disk as complementary technologies in an overarching backup plan, such as 3-2-1. Disk provides quick restores, while tape is the most cost-effective option for large, infrequently accessed data sets and long-term archiving, and can also provide ransomware protection via physical air gapping.