Storage and archiving in the cloud

The information storage is provided by a computer scientist’s device. The current technologies for storing are themass memories(hard drive, SSD card or microSD) or thefast access memorieslike the RAM memory (Random Access Memory) and laptops. When written on a mass storage device, the information stays there even after a power failure. When you write in a RAM and there is a

30 Guidelines to improve the use of cloud computing in education in the Arab countries, 2016

1.4 Data Hosting and Cloud Computing

power failure, the information is lost. The advantage of RAM memories is that the access duration, read and write rates are much higher than those of a mass storage device. However, for an equivalent price, a mass storage device provides a storage capacity far greater than a RAM.

A conventional hard disk is a set of trays with a magnetic surface which, like a tape, records information through the movement of the read-write heads, attached to the arms. All of these arms are called the comb. Thanks to the rapid rotation of the disk (from 5400 to 15000 revolutions / minute) the reading head floats above the surface of the magnetic disk, at a comparable distance to the width of a fly between the landing ground of an A320 and the tarmac. This technology reaches its limits and uses the properties of a less intuitive mechanism called a tunnel effect in quantum mechanics. Its response time is measured in milliseconds or 10-3 seconds (about 15 ms).

The SSD card, on the other hand, is an electronic mass memory mechanism based on electronic components capable of storing information without power supply, but whose read and write response times are much better than those of the hard disks, but less good than those of the RAM or the fast accessing RAM. Its response time is measured in milliseconds (about 0.1 ms) of the RAM is 10 nanoseconds (10 10-9 seconds).

In terms of cost, we have the following simple ranking: 1 GB mechanical hard disk <1 GB in SSD mass memory <1 GB in active RAM.

These technologies are evolving and the decline in the cost of their manufacture is contributing greatly. We are currently talking about NVRAM (Non Volatile RAM) which should be a standard for our machines in the near future, and promises 100 times faster access times than the SSDs. This technology aims to keep both the benefits of the RAM and the media. The most known current NVRAM technology is flash memory. NVRAMs potentially impact the organization of memory on a computer system. The organization is hierarchical with high-speed access memories, on the top of the hierarchy and in the bottom of the hierarchy, are "slow" but with large-capacity memories.

NVRAMs remove one level in the hierarchy. This is a phenomenon which has always existed: floppy disks 5"^1/4 have been replaced by other media which at the same time would be also replaced one day or the other. The CD-ROM for example is disappearing.

R A technical presentation of NVRAM technology and its integration into IT systems is available online³¹. It’s about a presentation performed as part of the international workshop, High Performance Data Intensive Computing (HPDIC) in Phoenix, Arizona. This presentation is for computer scientists’ audience.

In the past, wearchiveda document when it was in the end of the life cycle. Archiving today is implemented immediately from the beginning of the documents’ creation, which are enriched throughout their life cycle. However, it is important to differentiate archiving from storage and backup.

Definition 16 Storage concerns actions, tools and methods for storing electronic content. The backup concerns all the actions, tools and methods intended to duplicate original electronic contents, in order to secure the contents and to prevent their loss. Finally, electronic archiving concerns all the actions, tools and methods used to gather, identify, select, classify and preserve electronic content in the very long term.

31 Future server platforms: persistent memory for data-intensive applications, S. Kannan and A. Gavrilovska, 2014

In the cloud, it is possible to rent storage space. Let’s take here the example of Amazon’s S3 service. We are not talking here about Dropbox rentals, as we want to discuss the storage service as the service among other services and not as an isolated one which is only utilized to store photos for example. It must be recognized, however, many services use the S3 whenever necessary.

The Amazon service S3³²had been launched in 2006. It is usually coupled with the service EC2 (Elastic Compute cloud) which concerns the calculation of the rental services (on files managed by S3³³). The S3 service comes in the form of a range of storage classes designed for different usable cases. The user pays according to the chosen storage class. This economic model is also applied for S2. With S3 the user can choose the class he or she wants according to his or her needs. It has some subtleties like the ability to use "Reduced Redundant Storage (RRS) is an Amazon S3 storage option which allows customers to reduce costs by storing non-critical repeatable data, at lower redundancy levels, than Amazon S3 standard storage".

The professions of librarians (see 1.5.4) and reference librarians are particularly concerned with archiving. The computer scientist builds tools to make life easier for all the tasks which we have just mentioned, as more and more media to be archived are in electronic form.

For the general public or professionals, Amazon offers since 2012 a long-term archiving and backup service. This is the Glacier service³⁴. Amazon Glacier is suitable for data which are not accessed very frequently and for which a recovery time of 3 to 5 hours is quite acceptable. The cost’s offer is also interesting since an offer starts from 0,007 USD per gigabyte and per month. Amazon claims that the service is secure for both data transfer and automatic encryption on the hosting site.

One of the benefits of the Amazon services which we just talked about, is the ability to interface them in a simple way via an API (Application Programming Interface) standardized type, for example REST (REpresentational State Transfer³⁵). When interfaces are standardized, ecosystems pop up more easily. This explains, for example many inventory software packages are using the readily available Amazon’s infrastructure. REST is an architectural style which applies as much to the implementation of the applications by a human user, as to the architectures oriented services’

implementation targeted for the communication between machines.

Finally, it is worth mentioning initiatives such as Owncloud³⁶and Seafile³⁷which offer complete solutions (on the server as well as on the client sides) for file backup. They replace the service with many advantageous "in the Dropbox". These are two cloud-based open source (SaaS) solutions which an university can deploy for its own uses. The University of Strasbourg uses Seafile and Owncloud is used in Reims with the computing cluster. Collaborative, synchronization, sharing and file encryption aspects are particularly well studied in these solutions.

32 Service Amazon S3