Tape drives have been used for data backups since the 1950s. They were the main backup storage medium for decades before being largely replaced by hard disk drives and cloud storage. However, tape drives still have some advantages for backup purposes in certain use cases.
What are tape drives?
Tape drives are data storage devices that write data to and read data from a magnetic tape. The tape itself is usually housed in a cartridge or cassette for protection. Tape drives are sequential access devices, meaning data is stored sequentially along the length of the tape. To access specific data, the tape drive must scan forwards or backwards to the correct position on the tape.
There are several formats of tape drives, but some of the most common are LTO, DLT, AIT, and VXA. The main factors differentiating tape drive formats are capacity, transfer speed, and compression algorithms. For example, the latest LTO-9 drives can hold 18TB uncompressed or 45TB compressed per cartridge.
What are the advantages of tape drives for backup?
Here are some of the main benefits of using tape drives for data backups:
- High capacity – Single tapes can store huge amounts of data, from terabytes up to around 100TB for the very largest formats.
- Low cost per GB – The actual $/GB cost of storing data on tape is very low, especially with compression.
- Long-term retention – Tape cartridges can store data for 20-30 years if stored properly.
- Portability – Tapes are easy to transport offsite for disaster recovery purposes.
- Linear access – Tapes must be read linearly, making malware less likely to spread through backups.
- Fast sequential speeds – Tape drives can stream data to/from tapes quickly in a sequential fashion.
In summary, tape offers very high capacities with a low cost per gigabyte, making them efficient for storing large amounts of archival and backup data. The linear format also provides protection against malware. And tapes are easy to take offsite for disaster recovery purposes.
What are the downsides of tape drives?
Tape drives also come with some disadvantages, including:
- Slow seek times – Finding and accessing specific data on tape can be very slow compared to disk.
- Compression impacts speeds – Many tape formats rely on compression to achieve maximum capacities. This compression/decompression adds some overhead.
- Mechanical parts – Tape drives contain moving mechanical parts that can break down and require periodic replacement.
- Serial access – Data must be read/written sequentially, unlike the random access of hard disk drives.
- Size and portability – While portability can be an advantage, the physical tapes still need to be stored and transported carefully.
- Drive compatibility – Reading old tapes may require compatible (obsolete) tape drive hardware and software.
In essence, while tape offers very high capacities for long-term data archiving, actually accessing and restoring data from tape can be much slower than disk-based backups. The mechanical nature of tapes also means drives require careful maintenance and old media needs compatible hardware.
When are tape drives ideal for backup?
Here are some of the main use cases where tape drives shine for data backups:
- Long-term archival storage – The high capacities, low cost, and long media lifespan make tape well-suited for archiving data that doesn’t need frequent access but needs to be retained for regulatory compliance or historical purposes.
- Backups of large datasets – The high throughput streaming speeds of tape drives make them efficient for large backups that would take too long or cost too much on disks, such as backups of big data, surveillance footage, or scientific data.
- Offsite disaster recovery – Tape’s portability enables easy transportation for offsite vaulting to guard against data loss from onsite disasters like fires, floods, etc.
- Backup targets – Tape drives can be used as inexpensive targets for regular backups from disk before eventually moving to archival tape.
In general, tape drives work best for large, sequential data that doesn’t need frequent access and can be archived for long time periods. The actual restoration of data from tape to disk still tends to be too slow for regular backups.
What types of tape drives are available?
There are a few main options for tape drive technologies:
- LTO (Linear Tape Open) – Currently the most popular technology, using open standards and multiple vendors. Current models go up to LTO-9 with 18TB native capacity.
- Oracle T10000 – Oracle’s format goes up to T10000 T2 drives with 8.5TB native capacity per cartridge.
- IBM 3592 – IBM’s proprietary format used in mainframes and high-end servers. The TS1150 model stores up to 20TB native.
- Quantum Scalar i3/i6 – Two Quantum tape lines topping out at 5.4TB and 11TB native capacity respectively.
LTO is generally the most cost-effective choice for most users, while formats like Oracle T10000 and IBM 3592 target higher-end enterprise servers and mainframes. But all provide high capacities and throughputs for backup and archiving purposes.
How fast are tape drives?
Transfer speeds vary across different tape drive models, but the latest options can achieve streaming throughputs up to 750MB/sec for compressed data. Here are some sample native transfer speeds:
| Drive Format | Transfer Speed |
|---|---|
| LTO-9 | 400 MB/sec |
| Oracle T10000 T2 | 252 MB/sec |
| IBM 3592 TS1150 | 360 MB/sec |
These speeds make tape drives suitable for streaming backups of hundreds of megabytes to gigabytes per second. However, seek times to locate specific data on tape are much slower at around 100 seconds on average.
How much data can tape drives store?
Storage capacities of tape cartridges have grown enormously over the decades, to the point where a single cartridge can store tens of terabytes of data. Here are native capacities of current midrange and enterprise tape drive formats:
| Drive Format | Native Capacity |
|---|---|
| LTO-9 | 18 TB |
| Oracle T10000 T2 | 8.5 TB |
| IBM 3592 TS1150 | 20 TB |
Note these figures are for native uncompressed capacities. Most tape drives use compression to effectively double or triple the usable capacity per cartridge. So a single LTO-9 tape can hold 45-90TB compressed!
What are the main tape backup software solutions?
Here are some of the top backup software platforms that support writing backups to and restoring from tape drives:
- Veritas NetBackup – Feature-rich enterprise backup software with broad platform and integration support.
- Veeam Backup & Replication – Virtualization-focused backup app also supporting physical systems.
- Commvault – Unified data protection and management for varied environments.
- IBM Spectrum Protect – Enterprise tape backup manager formerly known as Tivoli Storage Manager.
- Arcserve UDP – Long-running backup solution good for heterogeneous environments.
Most major enterprise backup suites either natively support tape devices or integrate tightly with specialized tape backup software like Oracle Secure Backup or IBM Spectrum Archive.
What are the typical steps in a tape backup process?
A typical tape-based backup procedure involves several main steps:
- The backup software scans the source data and determines changes since the last backup.
- A robotic tape library mounts the appropriate tape cartridge into a drive.
- The backup software writes the changed data from disk to the mounted tape.
- Once full, the tape is unmounted and returned to a storage slot by the robot.
- To restore data, the robot fetches the required tape and mounts it to stream data back to disk.
- Used tapes can be removed from the library and stored offsite for disaster recovery.
Larger tape libraries may contain multiple drives to allow parallel backups to different cartridges. Tapes may also be manually rotated on a periodic basis, such as weekly or monthly.
What is the typical lifespan of tape cartridges?
With proper storage, tape cartridges can retain data for decades. Here are typical media lifespans provided by manufacturers:
| Tape Format | Lifespan |
|---|---|
| LTO-5 to LTO-9 | 30 years |
| Oracle T10000 T2 | 30 years |
| IBM 3592 | 30 years |
To achieve these lifespans, tapes should be stored in temperature and humidity controlled environments. Tapes should also be rewound fully before removal from drives. With good conditions, tape retention periods can exceed 30 years.
How reliable are modern tape drives and media?
The reliability of tape drives and media has improved substantially over earlier decades. Here are sample reliability metrics:
- Bit error rate – Around 1 error in 10^17 to 10^19 bits read, multiple orders of magnitude better than HDDs.
- Drive MTBF – LTO drives have mean time between failures (MTBF) of 250,000 to 500,000 hours.
- Media defects – Modern tape media sees less than 1% of cartridges develop errors over the lifespan.
Combined with built-in error checking and correction, these factors make modern tape extremely reliable for long-term storage. Defective media can be detected and mapped out of use.
What are the typical costs for tape drives and media?
Tape drives and cartridges range in cost from affordable LTO options to high-end enterprise products:
| Item | Sample Cost |
|---|---|
| LTO-8 drive | $3,000 – $4,000 |
| LTO-9 drive | $4,000 – $6,000 |
| LTO-8 cartridge | $100 – $150 |
| Oracle T10000 T2 drive | $10,000 – $15,000 |
| T10000 T2 cartridge | $200 – $300 |
When calculating the overall costs, factors like expected compression ratios, media lifespans, and number of drives required need to be considered. But generally tape provides very low costs per gigabytes stored in most scenarios.
Conclusion
Tape drives still occupy an important role in the modern data center for specific backup, archive, and disaster recovery needs. While seek times are slow, streaming speeds continue to improve and per-gigabyte costs are far lower than primary storage. When long-term retention, large capacities, and offline storage are required, tape is hard to beat.
For smaller backups that need frequent restoration, disk-based backups are faster and more convenient. The cloud also now offers a viable alternative to physical tapes for offsite data retention. But for mass data that rarely needs restoration, tape remains a compelling storage medium.
Overall, tape drives are a proven technology that excels at high-capacity, low-cost data archiving and backup storage, especially for larger datasets. But careful selection of drive formats and integration with backup software is needed to make the most effective use of tape.
