Magnetic tape has been used for data storage and backup since the early days of computing. Tape offers some advantages over other storage media like hard disks and solid state drives, which has allowed it to persist despite the emergence of newer technologies. However, tape also has some disadvantages that limit its applications today. Let’s look at the pros and cons of using magnetic tape for backup in 2023.
– Magnetic tape has very high storage density and low cost per gigabyte compared to HDDs and SSDs. This makes it good for archiving large volumes of data.
– Tape has inherent physical protection. The media is enclosed in a cartridge so it is not subject to accidental erasure or corruption that could happen with disks.
– Tapes can be easily transported and stored offline. This provides an air gap against cyber attacks compared to always-online disk backups.
– The sequential access of tape makes restores much slower than random access disks. This limits its use for rapid data recovery.
– Tape has a limited number of read/write passes before requiring replacement. Disks can be rewritten virtually infinite times.
Advantages of Tape for Backup
High Storage Density and Low Cost
The main advantage of magnetic tape is its very high storage density. Modern tape cartridges using technologies like LTO-8 can hold up to 12 TB per cartridge. This storage density comes at a low cost per gigabyte compared to hard disk drives (HDDs) and solid state drives (SSDs). The actual media cost for tape can be as low as 1-2 cents per GB.
This high density and low cost makes tape ideal for archiving large volumes of data. Backing up petabytes of data is affordable with tape in a way that would be prohibitively expensive using HDDs or SSDs. While the drive costs are higher for tape, the media costs are much lower per terabyte.
Physical Protection in Enclosed Cartridges
Another advantage of tape is the physical protection provided by the cartridges. HDDs and SSDs are susceptible to damage and corruption if exposed to strong magnetic fields or physical shocks and vibration. Tape cartridges completely enclose the media and protect it from environmental threats.
This makes tape a more robust medium for long-term data retention. There is no risk of accidentally reformatting or overwriting data on tape like there is with always-on HDDs and SSDs. The cartridges must be manually inserted by a human operator to be accessed.
Portability and Offline Storage
The enclosed cartridges also make tape extremely portable. Tapes are lightweight and durable enough to be easily transported and stored offline. This is beneficial for backup because it provides physical separation between the live data and the backup copy.
Storing backup tapes offline and off-site protects against site disasters like fires, floods, or ransomware attacks that could impact locally attached disks. The offline nature also protects against cyber attacks since there is an air gap between the network and the tape backup.
Tape formats like LTO have maintained backwards compatibility even as capacities have increased. For example, an LTO-8 drive can read and write tapes from the previous two generations LTO-7 and LTO-6. This provides some protection against data loss if older media needs to be accessed after a migration.
In contrast, HDD interfaces and connections are not always backwards compatible. This requires more active data migration planning with disk-based backups.
Disadvantages of Tape for Backup
Slow Sequential Access
While tape offers advantages for archival storage, it has some significant limitations that make it less desirable for active backup and recovery use cases. The primary disadvantage is the sequential access and slow data transfer rates of tape.
The tape drive must physically wind the media forwards or backwards to locate the requested data. This sequential access means that recovery time objectives (RTOs) for tape will be several hours at best compared to the minutes possible with random access HDDs and SSDs.
Restores from tape may involve manually retrieving and loading the media, locating the backup files on the tape, and sequentially reading the data back onto disk before applications can access it. If large volumes of data need to be restored, this process can take days.
Limited Rewrite Capability
Tape cartridges have a limited number of passes before requiring replacement. Most LTO tapes are rated for several hundred full rewrites. In contrast, HDDs and SSDs can be rewritten virtually infinite times with no degradation.
This means tape has to be handled more carefully during re-use to prevent wearing out the media prematurely. Backup software needs to efficiently consolidate incremental backups and manage the tape pool.
With disk backups, there is more flexibility to modify backup schedules and retention policies since rewriting does not wear out the media. Tape requires more long-term capacity planning to get maximum usage from each tape.
Higher Latency Than Disk
In addition to the sequential access constraint, tape also has far higher latency than HDDs and SSDs for locating and loading requested data. Seek time for tape media can be 30 seconds or more, compared to just a few milliseconds for disk.
The initial load time tends to dominate for tape, so this high latency is less noticeable for large sequential reads. However, for smaller random accesses, tape performance suffers from these delays.
This makes tape a poor fit for backup scenarios requiring frequent media changes or partial restores of smaller datasets. The high latency and limited random access frustrates users accustomed to the speed of disk and flash storage.
Cost and Complexity of Automation
While the media costs for tape are low, specialized tape libraries add significant expense for automation. Tape autoloaders and robotic libraries are required to remove human intervention for handling multiple cartridges.
This automation adds complexity in terms of maintenance, robotics calibration, import/export slots, and additional software management. Provisioning and scaling capacity requires careful planning due to the automation requirements.
In contrast, disk-based backup can more easily scale storage capacity on demand. And backups to local disk or public cloud can be automated without physical tape handling robotics.
Use Cases for Tape Backup in 2023
Archival Data Storage
The low cost and high capacity of tape make it ideal for archiving data that needs to be retained for compliance or regulatory purposes, but is accessed infrequently. This “cold data” requires cost-efficient storage at scale. Slow access times are less important since the data is not actively used in business operations.
The media lifespan of 30+ years and portability also provide long-term security for archived data. Tape is proven technology trusted by organizations with large archives including scientific data, medical/healthcare records, financial records, and national archives.
Backup for High Data Growth
Organizations projecting significant long-term data growth can benefit from tape for backup purposes. The higher storage density and scalability make tape more cost-efficient for long-term retention of backup copies.
For example, a small business may opt for easy disk backups initially. But large enterprises may choose tape libraries to accommodate needs for 100 TB+ of backup capacity that will grow predictably over 10+ years.
Offline Backup for Cyber Resilience
By storing tapes offline and off-site, organizations can create an isolated, air-gapped backup copy as protection against cyber threats. Ransomware has increased interest in this offline tape backup approach as disk-based backup solutions face growing risks of encryption by malware.
Restoring large backup sets from tape adds significant workload complexity versus virtual machine or database restores from disk. But tape provides assurance that a clean offline copy exists beyond the reach of cyber attacks affecting production systems and network accessible backups.
Recommendations for Using Tape in 2023
Here are some best practice recommendations on deploying tape backup infrastructure in 2023:
– Evaluate the overall RTO and RPO needs before choosing tape. It offers physical protection for archived data, but does not provide quick recovery.
– Explore a disk staging tier to cache recent backups on HDD/SSD before writing a second copy to tape. This improves recovery time for accessing newer backups.
– Use multiple media types and off-site vaulting to maximize resilience against disasters. Don’t rely solely on tape as a single point of failure.
– Calculate long-term capacity needs and plan the tape library size accordingly. Upgrading automation down the road adds complexity and cost.
– Weigh using public cloud archival storage as an alternative to buying a tape library. Cloud offers other benefits like geographic distribution.
– Standardize on LTO media and drives for least risk of product obsolescence. LTO has wide industry adoption and a roadmap through LTO-12 currently.
– Leverage backup software that can manage tape media across the lifecycle – writing, reading, reusing, and retiring when worn out.
Magnetic tape retains important advantages for high density long-term storage at low cost. The offline aspect also provides security benefits for protecting backup copies against cyber threats. Tape remains well suited for archival data and large scale backup capacity that needs to be retained and grown over time.
However, the disadvantages of tape mean it is no longer optimal for primary backup targets that require rapid recovery. Most organizations use disk-based backups locally and in public cloud for operational recovery needs. Tape serves as a secondary storage tier focused on economics and isolation rather than performance.
IT leaders weighing tape backup need to consider both the advantages and limitations compared to replacements like public cloud archival storage services. Organizations with petabyte scale retention needs may still find tape provides the most cost-efficient solution for long-term storage diversity. But tape should be complemented with recovery-focused backups on disk or cloud.