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Computing and Information Services

Data Storage J: and S: drive

Using Snapshots to Recover Files

Regular backups (or "snapshots"), are taken from what is commonly known as the J: Drive and also the S: drive. These may be used to recover old versions of files, in the cases where you have either deleted them, or damaged them with inappropriate edits etc.

These snapshots can be access using either an NPCS, MDS or a standalone machine.

Snapshots are taken hourly during working day. These will appear on users’ J: drives, and can be accessed using Windows Explorer (See below). The snapshots have names like 09.00.hourly, 10.00.hourly, 11.00. hourly, etc.

If you are not using an NPCS or MDS machine you will need to map this drive (see below).

You can navigate through these to display complete saved copies of your files, and then simply drag-and-drop files back to your current J: drive or any other drive provided there is enough space. During the course of the day, nine of these snapshots are allowed to accumulate, and they are all deleted at 02:30 the next day, ready for the start of a new set.

Further snapshots are taken in the early hours of the morning, reflecting the work of the previous day.


• Saturday's snapshots are labelled as weekly snapshots.


• Snapshots for the last day of the month are labelled as monthly snapshots.


• All other snapshots are labelled as daily snapshots.

They have names like 050116.weekly, 050201.monthly, 050118.daily etc., and we keep the a number of  the most recent  snapshots. Note however that we cannot guarantee the numbers of these that we hold, as this will be dependent upon available space. Also note that snapshots are "pruned" so that there are more snapshots available for recent dates.

We believe that this system gives you valuable (but not absolute) protection against the usual patterns of file editing and accidental deletion – for important work you should still periodically back up a file you are editing to one of a different name.

Note that the method of storing the snapshots means that the older the file you wish to retrieve, the fewer copies that exist. In the case of a 3-month old file, for example, you have only the monthly snapshots from which to extract a version (the daily and weekly snapshots would have been deleted for a file this old), and you may have done some considerable editing after the file was saved in a monthly snapshot. So you cannot guarantee an up-to-date version of a particular file. Also, it is always possible that you create and delete a file which is never saved in a snapshot.

Accessing J: drive snapshots on an NPCS or MDS machine

To access your snapshots you must first open Windows Explorer. This can be done in a variety of different ways.

1 Click on Start | Programs | Windows Explorer
2 Right Click on the Start button and then select Explore
3 Right click on My Computer and then select Explore

In the Windows Explorer address box shown below type the following:


You should now see a selection of snapshots in the right hand window. You can navigate through the folders and see complete saved copies of your J: drive. To view any file(s) you must copy them to another location such as your C: drive or another folder on your J: drive.

Mapping your J: drive on a standalone pc

Firstly open the map network drive window. This can be done either by:

1 Right click on My Computer and select map network drive

2 From within Windows Explorer click on Tools | Map network drive

You should now be faced with the following window.

From the Drive dropdown list select the J: drive. Note for consistency we recommend you select the J: drive as your drive letter however it isn’t imperative that you do so.

In the Folder box type the following:



\\stevens\staff\dcl0ng for a member of staff on MDS

\\hudson\pg\dcl0ng for a postgraduate

List of staff categories

If you have any difficulty in identifying which category you belong to please contact the Service Desk for further help.

Click on ‘Connect using a different user name’ link and a ‘Connect As’ window will appear.

In the User name box type the following


Then in the password box type your CIS Password and click OK.

Now click on Finish.

You should now be able to access your J: drive and your snapshots via Windows Explorer or My Computer. For further information on how to view the snapshots please read above on ‘Accessing your J: drive’.

Unix users

The retention policies above all apply, and the snapshot directory is available as .snapshot in your home directory.

Tape Backups

Please note, we cannot guarantee the availability of a snapshot for a particular day, as these are managed in light of available space. However, regular backups to tape are also taken, and in the event that you cannot recover a particular version of a file, it may be possible to recover it from backup tapes, though this must be requested via the Service Desk and will take longer as tapes are stored off-site