How do you transfer large data files?
Large data files cannot be sent by email because they exceed the file size limit of most common email servers. So, how can large data files be transfered from a local computer to a distant one?
There are many aspects to consider when dealing with data transfer, but the most important are:
- the data size
- the capacity or bandwidth of the network links between your local computer and the distant computer
- data security
Data size and bandwidth are tightly linked since transferring large volumes of data on a low bandwidth network will be so time consuming that it could be simpler to send the data on a hard drive through carrier services.
Hard transfer - Hard drive transfer is a good solution for very large scale transfers, for example those supporting petabytes of data. Such transfers are available for many compute clouds, such as Amazon Snowball or Azure Data Box.
Sharing - Rather than perform large transfers, it may be easier to synchronize your local data storage with remote storage, or to use remote storage as a local drive. Common examples of this are Microsoft Azure Drive and Google Drive. The storage can be used by remote services.
Analysis - Cloud-based analysis systems include mechanisms for transferring data to and from the Cloud. Such systems include Microsoft Azure, Amazon Web Services, nextCloud and ownCloud.
If you intend to transfer sensitive data to another location, you have to check the regulation and security measures on the remote site. You can interact with the IT departments at both locations in order to establish your strategy. Do not forget to check the Human Data pages of the RDMkit.
Since data transfer involves so many technical aspects, it is a good idea to interact with your technical/IT team in order to avoid any problem if you want to transfer large amounts of data.
Step 1: Optimise data transfer
It can be very useful to archive your data in a single file to optimise and ease the data transfer. This can be done with two tools available on most systems.
- tar (tape archive) will create an archive, a single file containing several files or directories.
- gzip: since tar does not compress the archive created, a compression tool such as gzip is often used to reduce the size of the archive.
Step 2: Choose an appropriate data transfer protocol or application
The most common data transfer applications available are:
- FTP (File Transfer Protocol): Be sure to use a secure version of this protocol, such as FTPS or SFTP (SSH File Transfer Protocol). FTP will transfer files between a client and an FTP server, which will require an account in order to transfer the files.
- HTTP (HyperText Transfer Protocol):
- Rsync (remote synchronization): can be used to transfer files between two computers and to keep the files synchronized between these two computers.
- SCP (secure copy): SCP will securely transfer files between a client and a server. It will require an account on the server and can use SSH key based authentication.
These applications are suitable for small to mid size data. These applications are available on any operating system and can be used either through command-line (directly or with tools like cURL) or through a graphical interface.
For massive amounts of data, additional protocols have been developed, parallelizing the flow of data.
- Aspera Fasp
- GridFTP and Globus
These transfer solutions require commercial licences for your site and as such they are available mostly on large computational centres.
A comparison of file hosting systems is available on Wikipedia.
Cloud systems commonly have their own data transfer and data sharing systems. Your solutions then depend upon your choice of system. For very large data these include hard transfer. A useful comparison of cloud systems is on Wikipedia
Step 3: Check the transfer
During the transfer some data might become corrupted, thus it is important to check if the files you transfered have conserved their integrity. This can be done with hash algorithms. A checkshum file is calculated for each file before transfer and compared to a checksum calculated on the transferred files. If the checksums are the same, the files are not corrupted.
Relevant tools and resources
|Tool or resource||Description||Tags||Registry|
|Amazon Web Services||Amazon Web Services||storage data analysis transfer|
|Box||Cloud storage and file sharing service||storage IT support transfer|
|DropBox||Cloud storage and file sharing service||storage IT support transfer|
|Google Drive||Cloud Storage for Work and Home||storage transfer|
|iCloud||Data sharing||storage data analysis transfer|
|Microsoft Azure||Cloud storage and file sharing service from Microsoft||storage IT support transfer|
|NextCloud||As fully on-premises solution, Nextcloud Hub provides the benefits of online collaboration without the compliance and security risks.||storage IT support transfer|
|OwnCloud||Cloud storage and file sharing service||storage IT support transfer data analysis|
|Reva||Reva connects cloud storages and application providers||data analysis transfer|
|Rucio||Rucio - Scientific Data Management||storage data analysis transfer|
|ScienceMesh||ScienceMesh - frictionless scientific collaboration and access to research services||storage data analysis transfer|
|SeaFile||SeaFile File Synchronization and Share Solution||storage transfer|