Over the last few decades, the IT industry has been the battleground for a number of heated debates concerning the future of technology. One of the most interesting debates revolves around “Tape versus Disk” that has raged for years. Disk defenders have claimed that tape is dead for many years, while tape defenders claim that tape is strong and growing up, neither dead, nor dying like foot soldiers in the Civil War
It is time to call a truce
Both technologies; Disk and Tape, are still “alive and well”. The reports of the death of tape of “Disk-Only systems vendors” have been greatly exaggerated. Both disk and tape will exist in the data center for many years. The roles that disk and tape partake continue to evolve and are complementary. Let’s take a look at some of the myths that have circulated to prove that tape technology is a dying media type.
Myth #1: Tape is old technology …and old technology must be dead
Highlighting the early history of tape, the first commercially available tape drive, the IBM model 726, was introduced 55 years ago, in 1952. It used a 12-inch movie reel to store 1.4 megabytes of data and transferred data at 7.5 kilobits per second. So, is tape old? Perhaps, but it has had time to grow, evolve and be improved to become a reliable high performance technology. Today’s tape stores nearly a terabyte of data at speeds over 100MB per second. One might think that most modern technology has been developed recently…correct? Hardly! The early 1950s was an active time for computer manufacturers.
A Little Bit about Disk History
Some believe that disk drives came into scene much later than tape; however, only four-year gap between the two technologies. The first commercially-available disk drive appeared in 1956. IBM called this disk RAMAC (Random Access Method of Accounting and Control) which was 24 inches in diameter, had 50 platters and could hold about 5 megabytes of data. It rotated at a blazing rate of 1200 RPM. Compared to today’s technology, this disk was big, slow and expensive. The RAMAC system weighed about a ton, required a forklift to move it around, and you could lease it for about $3,500 a month. In the context of today’s standards, the early tape and disk drives were old technology, but there are other older technologies have also continued to evolve.
Myth #2: Tape cannot be improved any further
There are some believes that tape can no longer be improved and its technology has reached the limit. However, some points should be considered before taking for granted these perceptions. The first tape reel had a storage capacity of 1.4 megabytes of data. Today’s LTO-4 cartridge can store up to 800 gigabytes of data in an uncompressed format in one cartridge. This means that the capacity of tape in an uncompressed format has been increased by 571,426 times, over the last 55 years!
The fifth and sixth generation of LTO drives will continue LTO’s history of doubling the capacity and increasing performance with each new generation. Moreover, IBM has successfully tested in labs storing 8TB of data on a single cartridge and is working now on testing 100TB tape cartridge.
As for disks performance in this capacity race, today’s 1TB SATA drives are commonplace. These 1TB GB drives have increased the capacity of disk drives about 200,000 times over 51 years. This proves that increases in tape capacities have dramatically exceeded the pace of increases in disk capacities over the last 50 years.
Myth #3: Tapes failure
Every data center has experienced the failure of hardware or software components. Servers, disk systems and tape drives do fail as well. Hard disk drives are prone to failure, which is why the disk industry has invested a great deal of money in the development of better RAID solutions. Ask any road warrior about the reliability of their laptop and they will probably spend hours telling you stories about how the laptop was infected with a virus or just decided to stop working right before a critical presentation.
Those who worked in data centers at time when tape reels were round, not square, know better the problems with “round” tape operations. Tapes were manually threaded on tape drives. Tape vendors later encased the media inside square cartridges, thus preventing the media from being handled by operators. That helped to improve the operations and reliability greatly. Interestingly, the vast majority of tape-related backup problems are attributed to other sources than the tape hardware itself, such as system/software errors and human/administrative factors. Nevertheless, there have been numerous improvements in the magnetic media coating over the years since the days of reel-to-reel tapes. Today’s tape systems employ technology to provide outstanding data integrity characteristics. For instance, LTO technology uses servo tracking mechanisms and read after write verification that help ensure accurate reads and writes. In addition, LTO tapes use cartridge memory to store vital information to help maintain the viability of the system. Mean Time Between Failure (MTBF) for tape drives is calculated at the percentage of time that the drive is reading, verifying, or writing data. All of these characteristics help provide LTO drives with an impressive MTBF of 250,000 hours at 100% duty cycle. The first generation of DDS drive, available in 1989, claimed a MTBF of 300,000 hours at a 12% duty cycle; that is 36,000 hours at 100% duty cycle. LTO drives are about 700% more reliable than the first generation of DDS.
Of course, critical data should be written to two cartridges and one ported to a remote location to ensure that the data can be retrieved when needed in the event of a disaster. This removable portability is a key attribute of tape technology, which is not possible with disk to be treated as removable media.
Myth #4: Nobody buys tapes …anymore
Some claims that the tape market is no longer alive or active. Although some tape drives and tape cartridges have seen a decline in sales, this rule should not be generalized on the whole market. In fact, it is estimated that the tape market is over a $4-billion industry and the midrange segment continues to see impressive growth. Over 1.5 million LTO tape drives have shipped. The total number of tape petabytes shipped continues to show consistent growth. A major supplier of tape cartridges shipped about 600 petabytes of tape storage worldwide in the first quarter of 2003. This number increased to nearly 900 petabytes in the first quarter of 2004. In the beginning of 2005, the supplier shipped almost 1300 petabytes, which jumped to over 1700 petabytes in the first quarter of 2006, reflecting a growth rate of about 36% every year. This rate has increased to approximately 51% throughout the last three years. This means that Data centers are continuing to buy tape as a critical component of the storage hierarchy.
If data centers consider discharging the utilization of tape, where will the existing data be stored? Do we just throw away the tapes? Not likely! They contain historical data that need to be kept for a number of reasons including customer service requests, performance analysis, or compliance. We could take all of the archived information on tape and copy it to disk. How practical is that? Let’s say we have 10,000 tapes. There are 6,000 LTO-2 tapes (which store 400 GB of compressed data) and 4,000 LTO-3 tapes (storing 800 GB of compressed data). That is equivalent to:
6,000 LTO-2 tapes x 400 GB = 2.4 million GB
4,000 LTO-3 tapes x 800 GB = 3.2 million GB
This is a total tape capacity of 5.6 million GBs.
Consider the following:
A fully-populated SATA disk storage system can hold 56 TB (or 56,000 GB of data). We would need to buy 100 of these fully-populated disk storage systems
A high-performance disk array supports 332 TB of internal storage. We would need to purchase 17 of these fully-populated disk storage systems
You can replace your tapes with disk. It will take a lot of floor space – require dramatically increased power and cooling energy consumption and will cost a lot of money – but may make your disk salesperson very happy. This means that it is very expensive to replace tape with disk in medium-to-large data centers. Data centers will continue to use tape to store data.
By: Mohamed El Mofty
Storage Networking Solutions Expert
IBM Systems and Technology Group