Tape and disk storage have both played important roles in the history of computing. Tape storage dates back to the early days of mainframe computers in the 1950s, while the first hard disk drives emerged in the late 1950s and started becoming commonplace in personal computers by the 1980s.
Both technologies have their pros and cons. Tape offers very high capacities for storing data offline at low cost, making it well-suited for archival and backup use cases. However, tapes have very slow random access times compared to disk. Disk drives provide faster access and are better for online storage needs, but disks have traditionally had lower capacities and higher costs for large-scale data. The cloud has begun changing these dynamics, offering vast scale and low costs for cloud-based disk storage.
While disks continue advancing for primary storage, tape remains a popular choice for long-term data archiving thanks to its high capacity, low costs, and long media lifespan. Tape also provides a secure offline backup option not vulnerable to network outages. Determining which is “faster” depends greatly on the use case and access pattern.
Tape vs. Disk Speed
When it comes to read and write speeds, tape and disk storage have different strengths and weaknesses. Tape excels at sequential reads and writes, which means reading and writing large chunks of data in order. This makes tape well-suited for backup, archiving, and other large block data transfers (Altaro). However, tape performs poorly at random access, which is accessing small, non-contiguous blocks of data. Disk storage can handle both sequential and random access reasonably well.
The biggest advantage of disk is faster access times, especially for random access. According to Network World, disk can match speeds above 1 GB/s for both sequential and random workloads, while tape maxes out around 300 MB/s for streaming sequential data (Network World). So for applications requiring many small reads and writes, disk is significantly faster.
However, tape has the edge for sequential transfers of very large datasets. Tape storage systems with multiple drives can stripe data across tapes similar to RAID on disk. This allows data transfer rates up to 750 MB/s. Tape also has a much longer duty cycle, capable of sustaining high transfer rates for hours or days if needed (Tape Storage).
Tape Capacity
One of the main advantages of tape storage is its higher capacity compared to most hard drives. A standard LTO-9 tape cartridge can store up to 45 TB of compressed data, while the highest capacity consumer hard drives max out at around 20 TB [1]. Enterprise-class hard drives may reach 100 TB, but even that doesn’t match the potential capacity of a tape library with thousands of cartridges.
This makes tape ideal for long-term archiving of vast amounts of infrequently accessed data. While a single disk drive is limited, a tape library can scale to multiple petabytes of storage just by adding more tape slots and drives. The linear nature of tape also allows for very high sequential throughput as data is streamed from end to end.
Of course, accessing specific data on a tape is slower than on a disk due to the sequential operation. But for large archives and backups that are rarely retrieved, tape’s unmatched capacity and scalability trumps random access speed.
Access Time
One of the key differences between tape and disk is the access time, which refers to the time it takes to locate and retrieve data from storage. Disk storage provides much faster random access compared to tape. This is because disk drives use spinning platters that allow the read/write head to quickly move to any location and access data. Typical hard disk drives have an average access time of just a few milliseconds.
Tape drives, on the other hand, store data sequentially along the length of the tape. To access a particular piece of data, the tape drive must physically wind or rewind until it reaches the requested position. This makes access time much slower, often in the range of tens of seconds to minutes. Tape is designed for sequential streaming access from start to finish rather than random access.1
In summary, disk storage provides faster random access while tape is better suited for sequential data access and streaming.
Durability
When it comes to long-term storage, tape has a clear advantage in durability over hard disk drives. Tape cartridges are rated to last up to 30 years when stored properly, as noted in a report referenced by Iron Mountain: https://www.ironmountain.com/en-gb/resources/blogs-and-articles/d/disk-vs-tape-which-ones-game-for-the-long-term. In comparison, hard drives have an expected lifespan of around 10 years. Tape is substantially more reliable for archival storage spanning decades.
As pointed out on Reddit, tape’s longevity makes it very useful for long-term data retention: https://www.reddit.com/r/DataHoarder/comments/ecffmj/how_useful_are_tape_drives/. If data needs to be preserved and remain accessible for 20-30 years, tape is a much safer bet than hard drives.
Cost
When comparing tape and disk in terms of cost, there are a few key factors to consider. According to BackupWorks, tape has historically been about 8-10 times cheaper than disk in terms of storage acquisition and operation costs per GB. Tape cartridges can store massive amounts of data very inexpensively. For example, an LTO-7 tape cartridge providing 16TB of compressed capacity costs around $0.009 per GB according to Forbes.
However, tape has very high startup costs compared to disk. The tape drive hardware and autoloader robots are expensive initial investments. So while long-term storage costs are low, deploying a new tape infrastructure requires high upfront capital expenditure. Tape is ideal for large organizations with substantial archival needs, but is overkill for smaller data sets. Overall, tape provides the lowest $/GB storage costs but requires high initial hardware costs.
Use Cases
When it comes to whether to use tape or disk for data storage, much depends on the use case. Tape is ideal for long-term archival storage due to its high capacity, low cost per GB, and durability for data that needs to be saved for decades but is rarely accessed. Disk, on the other hand, excels for storing actively used data since it allows much faster access time.
As explained in The Tape Storage Market, “There are several use cases for tape storage: Long-term archiving: According to Fred Moore, president at Horison Information Strategies, tape’s low TCO makes it ideal for storing data for 10-30 years. Backup: Tape is the most popular backup storage media.” This long-term archival use case takes advantage of tapes’ ability to store vast amounts of cold data cheaply for decades.
Disk storage like SSDs and HDDs is better suited for data that needs to be accessed immediately and frequently. The much faster random access speeds of disks compared to serial access on tapes makes them the preferred choice for active datasets like databases, virtual machines, and web servers. Though disks have higher $/GB costs, their superior performance for active data makes them an optimal complement to tape archiving.
The Cloud
Cloud storage services like Amazon S3, Microsoft Azure, and Google Cloud are taking over some traditional tape roles like archiving and backup. The cloud provides easy offsite storage without physical media handling and transit (Source). However, tape still has advantages for long-term archiving because it offers an air gap from the network, natural disaster protection, and avoids recurring monthly costs (Source). Tape capacities continue advancing while costs decline, so tape retains a role alongside cloud services. Cloud storage relies heavily on tape behind the scenes in hyperscale data centers (Source). The choice between tape and cloud depends on access needs, security requirements, and budget.
Final Verdict
When it comes to choosing between tape and disk for data storage, the final verdict depends largely on how the data will be used. Tape can’t be beat when it comes to cost-effectively storing massive amounts of “cold” data that needs to be retained but is rarely accessed or modified. But for data that is “hot” and needs to be frequently and quickly read or updated, disk is clearly the superior choice.
With its very low cost per terabyte, excellent longevity, and offline nature, tape is the undisputed leader for true archival data storage and backup. Major companies rely on tape for storing huge databases, media libraries, surveillance footage, scientific data, and more. But tape’s slower access times make it ill-suited for active, high-performance workloads. For hot data that requires fast, random access, high availability, and flexibility, spinning or flash disk storage is vastly better.
So in summary: for inactive data that can tolerate high latency, tape is unrivaled thanks to its very low TCO. But for rapidly changing data that needs high performance, disk is the clear winner. Understanding these core differences allows matching the right technology to the use case for optimized, cost-effective data storage solutions.
Key Takeaways
Tape and disk storage technologies each have their own advantages and disadvantages when it comes to speed, capacity, access time, durability, and cost. Here are some of the key takeaways from this discussion:
– Tape drives have very fast sequential data transfer speeds, but slow random access times. Disk drives are slower for sequential transfers, but provide much faster random access.
– Tape cartridges can store tremendous amounts of data with high capacities up to 60TB per cartridge. Disk drives range from gigabytes to tens of terabytes.
– Accessing a specific piece of data on tape requires physically winding to the right position, which takes time. Disk drives can access any data block instantly.
– Tape is more durable for long-term archiving, with estimated 30-year shelf life. Disks can suffer from mechanical failures and data degradation over time.
– Tape drives and media have lower cost per gigabyte compared to enterprise disk arrays.
– Tape is ideal for backup, archiving and data retention applications. Disks are better suited for frequent random access and lower latency requirements.
– The cloud combines disk performance with tape economics and durability for an optimal balance.
In summary, tape and disk each have advantages that make them useful for different storage needs. Understanding these tradeoffs allows selecting the right technology for a given use case.
