Transfer Cache (XFC)

What is the XFC?  

The Transfer Cache (XFC) provides large but very short-term temporary storage for use during data transfer tasks in/out of JASMIN. This is useful when the might involve assembling/manipluating data before moving it elsewhere.

Users are able to self-initiate the service for themselves, and will be granted folder on one of a number of shared storage volumes.

Users interact with the XFC in two ways:

1. to initialise their own XFC directory, a command-line client is used.
2. the directory can then be accessed via any data transfer tool (cp, mkdir, rm, mv, rsync, or Globus).

Using XFC  

JASMIN provides access to XFC via a command-line client: xfc

Once installed into your $HOME directory (using one of the sci servers), the xfc client can be run on either the sci (sci*.jasmin.ac.uk) or xfer (xfer*.jasmin.ac.uk) servers, but should NOT be run on the high-performance transfer servers hpxfer*.jasmin.ac.uk.

The client is used only for interacting with the service, but is not needed for accessing the storage it provides. The storage provided is mounted in most places across JASMIN: the path to your XFC volume is returned by the client in one of the steps shown below.

Users are expected to use the xfer servers or a high-performance data transfer service, or ideally Globus, to do any data transfers either within or in/out of JASMIN. This preserves resources for on the sci servers which are for general-purpose interactive computing.

The xfc client is used to initialise and then query the status of a user’s XFC storage directory:

To see all the available options: xfc -h

Initialise your XFC directory  

xfc init
** SUCCESS ** - user initiliazed with:
username: username
email: user.name@stfc.ac.uk
quota: 10TB  # IGNORE: quotas not currently active
path: /work/xfc/vol7/user_cache/username

The path is the path on the JASMIN system to this user’s XFC directory. Data can be put here using standard UNIX command-line tools cp, mv, rsync or Globus. Subdirectories can be created using mkdir. Change read/write permissions on the directories and files using chmod, etc.

Find out the path of your XFC directory:  

xfc path
/work/xfc/vol7/user_cache/username

Once you know the path, you can ls it, for example to check the permissions:

ls -ld /work/xfc/vol7/user_cache/username
drwx------ 13 username    users        4096 Oct 15 14:52 username

It is possible to change the permissions and groups of an XFC folder, for example, so that colleagues from the same group workspace can access it. However, please don’t regard this space as an extension of a GWS because data should not reside in the XFC folder for more than a few days/weeks.

Check usage  

To check your current usage, use the command pan_du -s:

pan_du -s /work/xfc/vol7/user_cache/username
dir /work/xfc/vol7/user_cache/username: 2 files, 1220860 KiB

Note on reported sizes:

• size is reported in binary kilobytes (KiB)
• to convert to binary terabytes (TiB), divide by 1024**3
• this needs to be divided by 1.3 for actual data size (for technical reasons to do with the storage system used)

A handy utility to check how long your data has been there, is the additional -a option:

pan_du -sa /work/xfc/vol7/user_cache/username
dir /work/xfc/vol7/user_cache/username: 2931 files, 424130252 KiB
age 30D: 0 files, 0 KiB
age 60D: 0 files, 0 KiB
age 90D: 0 files, 0 KiB
age 120D: 0 files, 0 KiB
age MAX: 2931 files, 424130252 KiB

This user has been storing data for far too long (MAX, i.e. beyond 120 days)! Please aim to keep your usage WELL below 30 days for this service.

Please DO NOT use touch or similar processes to alter the age of your files. Any use of this risks sanction from the JASMIN team.

Check free space on shared volume  

To check the amount of space free on the shared volume where your XFC folder sits: (using this command, sizes are reported in decimal terabytes)

$ pan_df -H /work/xfc/vol7
Filesystem             Size   Used  Avail Use% Mounted on
panfs://panmanager04.jc.rl.ac.uk//work/xfc/vol7
                       260T   162T    99T  63% /work/xfc/vol7

This shows that the volume size overall is 260 / 1.3 = 200 T (decimal terabytes), and that there are 162 / 1.3 = 124 T used, 99 / 1.3 = 76T free, or 63% usage.

Consult the man pages for pan_du and pan_df for further information.