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Tiered File System

The Tiered File System (a.k.a., tierfs) is additional space for users to store their files when they are less worried about the files being backed up.

Background

The tierfs is made up of multiple Linux-based file servers plus the NetApp filer. The large amount of disk space found on the Linux machines is not backed up with the regularity that is observed on the main filer. There are currently three tiers in the tierfs:

  • tier1: main filer (maytag)
  • tier2: these files are backed up once a week.
  • tier3: these files are never backed up.
The concept behind the tierfs is to extend the main filer's disk space with less-frequently backed-up space that need not be allocated by the tstaff as the main filer's space is. Files kept on the tierfs are to be as seamlessly incorporated into the main filer as possible. To achieve these goals, tierfs-tools have been authored to make it easy to move files back and forth and allocate space for one's self.

All interactions with the tierfs will be via symbolic links to files and directories within your working directory. These links are created by the tierfs-tools.

It is worth mentioning that, since these spaces are not part of the main filer, there are no .snapshots on files stored in this space. Equally note-worthy is that these disks are NFS mounted, making them accessible from all cs machines, making it more flexible than /ltmp.

Usage Guidelines

The tierfs space is available to all that need it; however, there are certain guidelines. For instance, Undergraduates are not permitted to use the tierfs from within their home directories. If an Undergraduate needs to use this space, he must first have permissions within a /course or /pro directory.

Generally speaking, when using the tierfs space, the same guidelines for space usage on the main filer should be observed on the tierfs -- keep your usage as streamlined as possible.

The tierfs is perfect for large, static data sets. This sort of data could be backed up once, moved to tier3, and then never backed-up again. Alternatively, if you think you may make infrequent changes, perhaps tier2, which has a very slow back-up schedule, would be better suited.

The tierfs-tools allow you to create a dumping directory to allow for file creation directly to the tierfs. This sort of thing would be perfect for programs that output large log files. Incidentally, /ltmp is also perfect for large log files, but the tierfs has the benefit of being on a raid system, which will offer dependability over /ltmp.

Caution: The tierfs gets cleaned out on a regular basis with a link-checking garbage collector. If you lose a link to a file in the tierfs, that file is subject to be removed. So, please make sure not to delete links! As a consequence, if your account gets removed from the system, your links will disappear and the files on the tierfs with them. If you lose a link, email problem@cs ASAP.

tierfs-tools

A suite of tools have been written to make using the tierfs easier. These are called the tierfs-tools and may be found in /local/bin/. The only program you should need to directly interact with is called 

%tierfs
usage: tierfs [-b] [-f] [-h] [-m ] <filename/directory>
  -b            put file(s) on tier2, which is backed-up
  -f            never prompt, always overwrite
  -h            print this help message
  -m <mode>     possible modes: 'mirror', 'mkdir', 'remove', and 'revert'
The first option is whether you want files to be backed up. If that is the case, give -b as an option, otherwise the program defaults to tier3. Secondly, you can choose to have the program not ask you when it comes across a situation it finds to be potentially harmful; use -f if you would like to not be asked. A mode must be chosen. The modes are as follows:
  • mirror: Move a file currently on the main filer to the tierfs.
  • mkdir: Create a link to a directory (to be created) on the tierfs.
  • remove: Delete a link to a file on the tierfs and the file itself.
  • revert: Move a file that is on the tierfs back on to the main filer.
If a mode is not given, the program will default to mirror mode. Lastly, a file or directory must be given. For mirror, this will be an existing file or directory. For mkdir, this will be the name of the link to be created. For remove and revert, it will be the name of the link to the file on the tierfs.

It is very important that you do not manually change the link in any way. That is, you should not move it or remove it because you will lose the file(s) that the link points to. Always use the tierfs-tools.

Windows Access

Windows clients have limited access to tier2 and tier3 file systems. The tierfs tool mentioned above is not available under Windows, but after space is created with the tool, Windows clients can read and write to it.

For example, after you create space with the linux comman,

tierfs -b -m mkdir /u/username/oldfiles

you'll find a symbolic link in that location that might point to

/tierfs/deepblue/tier2/home/username/oldfiles/

To access that directory under windows, point a browser to

y:\tierfs\deepblue\tier2\home\username\oldfiles\

Note that the last backslash is required, otherwise Windows will not find the directory. Also, at this time, Windows can only access directories created by the tierfs tool and not individual files. By default, the tierfs tool copies each file individually and places links to each one. Windows can only access directories created with the -m mkdir command with the tierfs tool.

Page Owner: Dorinda Moulton Last Modified: Thu Nov 3 12:57:10 2005