Costs of storage in sound archives

Radio Facilities Development.

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Costs of storage in sound archives

C.L. Doesburg
Hilversum, August 1988

Originally published in IASA Phonographic Bulletin No. 54 - July 1989

Note added in 2010: this paper looks at storage costs of physical carriers, rather than digital files. Although the type of carriers used in the following calculations etc are now obsolete, the underlying points made are still relevant today.

Table of contents


If we wish to obtain some insight into the costs of storing sound in an archive (meaning long-term storage), we do not deal exclusively with the costs of the information carrier but, rather, with the overall organisation of a sound archive. Although the costs of an information carrier in itself are not too high, the number of information carriers and the storage capacity required are important factors when determining the overall cost of an archive. The important question is, however, what is the storage cost in relation to the other “archive” costs?

In the first part of this report we concern ourselves with only one aspect of the overall costs, namely:

$ What costs are involved in information storage?

This leads to a few more questions such as “How can we define and quantify these costs?” Later in this report we will co-ordinate this with the overall archive costs.

The answer to the question “Why do we want to know?” is relevant to, for instance, the managers who will make the final and, hopefully, correct choice as to which information carrier should be used in an archive.

An important question is “What influence does the type of information carrier have on the cost of sound storage?”. It seems obvious that a smaller information carrier (such as using a R-DAT cassette in place of quarter inch tapes - the example used in this study) should provide a solution to the problem of making the best use of the available space. We have to prove, however, that this assumption is correct. In order to reach the correct decision, it is necessary that we determine the various calculation factors for sound storage and express these in a workable unit which can be the base for an accurate definition. In this way, it will be relatively simple to ascertain if the price of an information carrier is of great influence on the overall cost and if the operational qualities of that information carrier can be weighed against a cost reduction or a cost increase in the overall running cost.

What determines the archive costs?

We can define the four principal areas of which cost development is more or less independent. These areas certainly have a mutual influence and each area is not isolated. The various areas are the following:

$ The total cost of the archive structure - the appropriate part of the capital cost and the annual running costs - that holds the storage space.
$ The total annual cost of the staff working for the archive.
$ The annual cost of the raw materials such as the tapes, forms and office equipment which are necessary for the archive to operate.
$ The annual cost of the sound equipment needed to play-back the original information carriers and to copy it onto the archive carrier - again, part of the capital costs and the annual running costs.

Because it concerns a comparison between an analogue recording tape and a R-DAT cassette as archive carrier, our main interest at this stage is the calculation of the storage costs.

Which part of storage cost do we want to calculate?

In order to calculate the storage capacity we need the following information:

$ The cost of storing the information carrier. In other words: the cost of storing the carriers in a unit space divided by the number of carriers. One can call this the hard storage volume.

The product of an archive is the quantity of information that it holds. It is more correct to calculate the actual cost of the archive product:

$ The cost of storing the information. In other words: the cost of storing the information on the carriers in a unit space divided by the hours of information stored. This could be expressed as soft volume.

This is a handy starting point for calculation purposes.

What will we actually do with these cost figures?

Calculating the storage costs in relation to the archive costs allows us to look clearly at the measures which have to be taken to judge the quality or the continuity of the archive and to determine the importance of the effects of the measurements.

If we estimate, that in the coming decades we will have to deal with a decreasing margin between budget and cost, the following question could arise:

$ Should the storage costs per hour, which are dependent on housing costs in the long term:

* be increased.
* be decreased.
* stay the same.

If we make the above mentioned estimate, we come to the decision that the storage costs should be decreased. In other words:

$ The number of hours of information per cubic metre housing should be increased.

Why does the number of hours of information per cubic metre of housing have to be increased?

An archive is always expanding. Every year, new information to be stored is delivered to the archive. Advance selection of the information offered is not simple; even more so when selecting after a certain time and then destroying the information of lesser historic value. Selection costs time which equals money. This money is not related to the storage costs of the information. Only when the information carrier has to be replaced will it be the right moment to make this judgement.

Another fact; the expansion of storage space is always a abrupt action. We add more cubic metres of space and then, before adding yet more space, we have to wait until this new space is used up in turn. Our estimation that the ratio between budgets and costs in the future is decreasing is the final argument to reach the conclusion that “We have to store more information in the available space”.

The increase in the number of hours of information per cubic metre of housing is only possible, however, with the condition that this increase is made in such a manner that it is technically acceptable (considering the other requirements for safe information storage).

Regarding the storage costs, we have not taken into account, for instance, the following points:

$ The safety of the information; i.e. protecting information carriers against atmospheric conditions; against electronic faults; and against fire and theft.
$ The handling costs of information; i.e. copying from an information carrier onto a consumer tape for lending out; search documentation systems; and personal advice and administration.
$ The preservation of information; i.e. a technical system that will keep the information on a long-term basis.
$ The specific technical qualities of the various information carriers; i.e. special requirements of operating the equipment and the structural operating process, depending on the shape of the carrier (roll, disc or tape) and the recording technology (mechanical, magnetic or optical).

All these aspects are very important for the efficient running of an archive and must not be neglected when making the final decision on archiving. When deciding the organisation of an archive, it always requires the weighing of the available means against the risks to the collection.


Summarising this particular subject, storage costs, we have to note that:

$ Our main concern is the number of hours of information to be stored per cubic metre of housing.
$ We have to deal with the information housing costs per cubic metre.
$ We have to deal with the storage capacity of the carrier, i.e. the number of hours of information that can safely be stored on the carrier.
$ We do not consider the operational costs for staff and machines.


Reviewing all that we have discussed concerning the specific subject of storage costs, we can make the following conclusions:

$ In view of future expectations, a reduction in housing cost is desirable.
$ The number of hours information per cubic metre of housing has to be increased.
$ The storage capacity of an information carrier should be increased if safe to do so.
$ The operational costs are, as far as we know, not related to the storage costs. It remains to be seen, however, if operational costs can be decreased when using another information carrier, taking into account the special operational aspects, such as user-friendly facilities.

Practical example

A practical example is necessary to illustrate the way the above-mentioned facts work. The figures are derived from an existing archive and are subject to the usual work configuration. All figures used in this example are rounded off: the only purpose is to observe the ratio between them.

The basic facts of this archive are:

$ It uses analogue recording tapes with one hour storage capacity.
$ The size of the storage space - where cabinets and shelves are installed - is 25 cubic metre.
$ The cost of housing the complete archive is f. 70,000 a year.
$ The stored information is 12,500 hours.

The calculations

Using these figures, we can calculate that the number of hours of information per cubic metre of housing is 12500/25 = 500 hours.

Considering that one hour of information is, in fact, the “final product” of the archive, all the housing costs of the complete archive should be charged to the product. Therefore, a cubic metre of storage space costs 70000/25 = f.2,800 a year and, in this example, the storage of one hour of information costs 2800/500 = f.5.60 a year.

It seems clear that, with the space available in the existing store in mind, when using a information carrier with a higher storage capacity, the total number of hours of information stored can be increased, with the result that the annual storage costs per hour of information decrease.

An information carrier with a lot more storage capacity than the analogue recording tape used in this example is the R-DAT (Rotary-head Digital Audio Tape). Accepting that the size of an R-DAT cassette is much smaller and the recording capacity is three times as high as a professional audiotape, the use of R-DAT could create a great increase of storage capacity in an archive.

Using the same figures as before, we can make a comparison of analogue tape and R-DAT:

$ The measurements of an analogue recording tape are 0.27 x 0.27 x 0.015 = 1.09 x 10-3 cubic metre.
$ The measurements of a R-DAT cassette are 0.08 x 0.06 x 0.015 = 0.072 x 10-3 cubic metre.

The volume ratio between the formats is, therefore, 1.09/0.072 = 15.19:1.

The capacity of a R-DAT cassette is 3 hours. The information storage ratio between a R-DAT cassette and an analogue tape is, therefore, 3 x 15.19 = 45.57:1.

However, storage capacity is reduced when storing smaller objects: wasted space is increased. From past experience, it is necessary to introduce a correction factor of 0.8. This gives an increase of 45.57 x 0.8 = 36 times.

The conclusion is that the capacity of a storage space with R-DAT cassettes is 36 times higher than analogue tapes.

The cost of tapes and machines are about the same for R-DAT and analogue tape. At present, the price of a R-DAT-cassette is roughly the same as the price of an analogue tape. The price of a professional R-DAT-recorder (Pro-DAT) is about the same as the professional analogue audio-recorders normally used in archives.

We have ignored the costs of new shelving that is needed for housing the R-DAT cassettes. The most important fact is the possibility of increasing the storage capacity by 36 times and that results in the number of hours per cubic metre housing in this example to be increased to 36 x 500 = 18.000 hours.

Taking into account the figure of housing per cubic metre being f.2800, we can calculate that the storage costs of one hour information on a R-DAT cassette are 2800/18000 = f.0.16 a year: a dramatic and attractive reduction by a factor of 35 from the f.5.60 a year for analogue tape.

The example shows us the following:

$ The storage costs using analogue recording tape are 35 times more expensive as when using the R-DAT-cassette when using the same capacity storing space.
$ The existing archive space can be used for an extra 36 years at present production level.

The result that, when compared with using analogue tape, no building activities have to be undertaken to expand the storage space is, of course, very attractive. If one has to do so, the housing costs per year are increasing only slightly.

When re-calculating, we can compare the results with each other in order to make a decision. When we look at the storage costs only, and we do not take the other aspects of information carriers into account, the result of this comparison is very clear.


We do remember:

Which factors determine the archive costs?


$ The complete housing costs of the archive.
$ The work structure and the overall personnel costs.
$ The raw materials, for instance tapes etc.
$ The available equipment/machines.

Then - if we want to review the situation clearly - the most important question is really:

$ what are the actual storage costs in relation to the overall cost projection of the archive?

Again, the example figures are derived from an existing archive and are rounded off only for the purpose of illustrating the related ratio.

The other costs of the complete archive are as follows:

$ The personnel costs; f.750,000 a year.
$ The remaining costs related to the safety copy archive; the overheads of a complete company; the purchase of raw materials such as tapes and forms; costs of archiving documentation system; costs of a computer system; office equipment; equipment write-offs etc. are approximately f.580,000 a year.
$ The technical costs, such as write-off s, maintenance etc. of the audio equipment are f.150,000 a year.

A total of f. 1,480,000 a year.

Taking the storage capacity of 12,500 hours of information and considering that this information is the final product of the archive, we can calculate that the remaining costs for one hour of information are:

1480000/12500 = f.ll8.40 a year.

As the cost of R-DAT tapes and machines are about the same as for analogue tapes, the costs of running the R-DAT or an analogue archive are about the same. If it is assumed that, with holdings with a duration of 12500 hours, the analogue archive is full and the R-DAT archive holds copies of the same material, then the R-DAT archive has the capacity to increase its holdings by 12,500 hours each year for 36 years. This increase is clearly excessive and the potential life of the R-DAT archive will be greater than 36 years before any additional space is required.

Therefore, the remaining costs for one hour of information in the case of R-DAT are:

1480000/12500 = f.118.40 a year.


In the case of analogue tape, the total archive cost for one hour of information is: f.5.60 + f.118.40 = f.l24.00 a year.

In the case of R-DAT the total archive cost for one hour of information (considering an equal year's production) is: f.0.16 + f.118.40 = f.118.56 a year.

The total difference between using an analogue tape or a R-DAT-cassette as information carrier per hour information is f.5.44 a year. So every year gives a saving of 12,500 x 5.44 = f.68,000 on the total amount. For a good understanding of the ratio we have to consider that the total archive costs are f.l,550,000 a year (storage costs of f.70,000 plus the other costs of f.1,480,000).

Adding to this the statement that, in the case of analogue tape, the information storage space would have to be increased, while the use of R-DAT would not require any increase in space for many years, we can see that the relationship between the annual housing costs of f.70,000 and the overall annual overall cost of running the archive costs the comparison rather irrelevant.

Before making a final decision based on all the above arguments, we have, however, also consider that there is no real technical experience at present of the long-term viability of R-DAT and the technical problems are, as yet, unknown. Many technicians have doubts about the format

Final conclusion

Reviewing the above, the final conclusion is:

$ The storage costs per hour of information are marginal for analogue recording tape in relation to other costs of the archive.
$ The storage costs per hour of information are, when using R-DAT, even more marginal in relation to the other costs of the archive.

Taking into consideration all other aspects of both types of information carriers and compared to the eventual financial effects, the conclusion has to be:

$ The technical and operational aspects of the type of information carrier used are important to the overall functioning of the archive.
$ In contrast, the economic aspects of the type information carrier used are - when considered as part of the overall cost of running an archive - marginal for the overall continuity of the archive.

Other companies producing software-like products, such as radio and television programmes, have, in many cases, reached the same conclusions.

In other words:

Looking at a very narrow range of parameters we came to the conclusion that the calculation of the relative storage costs is, of course, useful. However, for the complete functioning of an archive including its management, we have to watch the total amount: not the storage figures alone.

If there is a real need for saving costs, looking at the “personnel costs” and the “remaining costs” can be more effective.