Maybe. It depends on where and when you lost the data.

Location of data to be recovered

• MathNet centralized file storage

  Home directory, Web directory, Mail inbox or folders, Windows desktop "Common" folder, pre-arranged nightly personal workstation backups.

• Public workstation's local storage

Desktop, Temporary folder.

Our centralized file storage contains the following data

The data contained in this storage is backup'd (snapshot) every hour at the top of the hour, and 10 hours' worth are kept. Additionally, nightly snapshots are taken every midnight and kept for 7 days. A weekly snapshot is also taken at Sunday midnight, and last 4 are kept. Thus, it is possible to retrieve data for up to 5 weeks.

Snapshots cannot be kept indefinitely, so it is important to retrieve lost data as soon as you are able to, otherwise it may be purged before you can get to them.

Retrieval from Snapshots

• Step 1: Understanding snapshot names

  Snapshot archives are available from our public Unix workstations. A subset of all available archives is also available from our public Windows workstations (e.g. ladybug, beetle). They contain exact replicas of the data at the time the snapshot was taken.

  Each snapshot archive have names that reflect the age of the snapshot.

  Snapshot names
  Unix	hourly.0, ..., hourly.9 These directories contain hourly snapshots taken at the top of the hour with hourly.0 being the most recent and hourly.9 being the oldest snapshot. nightly.0, ..., nightly.6 The nightly snapshots are taken at midnight daily, with nightly.0 being the most recent and nightly.6 being the oldest snapshot. weekly.0, ..., weekly.3 Weekly snapshots are taken at the start of Sunday at midnight; weekly.0 was taken at the most recent Sunday, and weekly.1 the Sunday previous to that, etc.
  Windows (UNC or Icon name)	hour or Last hour Same as "hourly.0" explained above. night or Last night Same as "nightly.0" explained above. week or Last Sunday Same as "weekly.0" explained above.

  No two snapshots are taken at the same time; if two snapshots coincide (e.g. at Sunday midnight, the hourly, nightly, and weeky snapshots coincide), the longer interval snapshot takes precedence and the rest skipped. So for example, at Tuesday 02h15, the list of snapshots in increasing age is

  hourly.0 (taken at Tuesday 02h00)
  hourly.1 (taken at Tuesday 01h00)
  nightly.0 (taken at Tuesday 00h00)
  hourly.2 (taken at Monday 23h00)
  ...

• Step 2: Finding which snapshot has your data

  It would be wise to recover data as soon as you realize it is gone. You have 4-5 weeks to recover your data before the oldest snapshots disappear. Furthermore, if the file is modified often, the hourly changes are only kept for 10 hours, then disappear, leaving only the nightly version available.

  In general, you should start searching for the data from the newest to the oldest snapshots. If you cannot remember the name of your lost data or when you lost it, you have a long search ahead of you.

  • (Unix)

    If you know the file or directory name of what you want to recover, for example,

    	~schmuk/Recipes/Goulash/spicy.txt

    you can use "ls" to look for that file sorted by modification time:

    	ls -lt /nfs/snap.home/*/schmuk/Recipes/Goulash/spicy.txt

    If this does not tell you which version you want, then you'll have to examine the contents of each snapshot version.

  • (Windows)

    Navigate the snapshot folders until you find the data you want to recover.

• Step 3: Recovering your data
  • (Unix)

    Once you have found your lost data, you must copy it out of the snapshot archives back into your home directory or wherever it should go. The snapshot archives are immutable, so you cannot delete, rename, or modify them.

    	cp /nfs/snap.home/hourly.0/schmuk/Recipes/Goulash/spicy.txt recover.txt

    If you've need to transfer a lot of files (e.g. a whole directory with zillions of files and subdirectories), you can use this method to copy an entire directory and its subdirectories:

    	cd /nfs/snap.home/hourly.0/schmuk/
    	tar cf - Recipes | (cd /some/safe/dir; tar xvf -)

  • (Windows)

    Copy the snapshot file/folder back onto your desktop or filespace (i.e. usual drag and drop operation).

  Public workstation's local storage

  Examples of data stored on public workstation's local storage are

  • Temporary directories such as

    Unix: /tmp, /var/tmp
    Windows: C:\TEMP

  • Data held on personal workstations and laptops that do not have pre-arranged nightly backups.
  • Windows: Files/folders on desktop, application folders.

  This data is not backed up. You can see the section Other Places to Look to help you recover lost data.

  Other Places to Look

  • Trash: some desktops (e.g. Windows, GNOME) will not remove files immediately, but place them in a temporary location represented by a trash can icon. It may still be there.
  • Application backups: some applications will make copies of data before modification. Look for filenames suffixed with '~', '.bak', '.old', '.sav', '.orig', '#', etc.
  • Email: if you have sent (or received) the data in the form of an Email attachment, it may still be in one of your mailboxes.
  • Recovery software: for personal workstation, file recovery software may be avilable that reovers deleted files. If the data is important, do not use the computer: use of the storage device may permanenlty overwrite your old data.
  • Copies: if you have received/sent copies from/to other people, they may be able to replace your copy.