What is HPSS?

HPSS (High Performance Storage System) allows you to store and retrieve large files in a relatively simple way. Instead of writing your files to tape, you can store files in your HPSS home directory, without worrying about bookkeeping issues.
It looks like a file system, which means that you can create your own directories in which you can store your files. With RFIO commands like "rfcp", "rfmkdir", "rfrm" etc. you can easily manage your files.
Storing large files in HPSS has some obvious advantages over the other storage possibilities you have:

No "garbage collecting" runs on HPSS. Little used files are moved from disk to tape, but this is transparant to the end user.

You can access other people's files. This can be very useful for group Ntuples and privately produced Monte Carlo sets. "pubarch" does not have this possibility.

No manual intervention is needed to stage in the files. Private user tapes normally are manually mounted, which can cause long delays outside office hours.
More information can be found here.

How can DELPHI users benefit from HPSS?

Currently, there are already many ways to store, archive and/or back-up DELPHI user files. HPSS is intended for large files (> 100 MB), and especially DSTs and large Ntuples are good candidates for storage in HPSS.
To access your HPSS files, you have to stage them in, with a command like

  delstage -M $HPSS_HOME/myfile.dst

As with usual tape staging, the contents of your file are copied onto the diskserver, and a symbolic link is created in your directory.

Practical points

everybody in Delphi has got an HPSS account now!
we have created an environment variable $HPSS_HOME which holds the name of your HPSS home directory, and its server:
```
  $HPSS_HOME = hpsssrv1:/hpss/cern.ch/user/u/username
```
you must use RFIO commands to manage your HPSS files:
- to list the contents of your HPSS home directory:
  rfdir $HPSS_HOME
- to create a subdirectory:
  rfmkdir $HPSS_HOME/dst
- to copy a file to your HPSS directory
  rfcp myfile.dst $HPSS_HOME/dst/file.1.dst
- to change a file name:
  rfrename $HPSS_HOME/dst/file.1.dst $HPSS_HOME/dst/ww98.1.dst
- to delete a file:
  rfrm $HPSS_HOME/dst/ww98.1.dst
delstage -M $HPSS_HOME/dst/ww98.1.dst stages in your file.
delstage -C -M $HPSS_HOME/dst/ww98.1.dst removes the staged file from the diskserver
PHDST is HPSS-aware. This means that you can specify your file like:
FILE=$HPSS_HOME/myfile.dst
in your PDLINPUT file.

Example

This part of a user script:

# create PDLINPUT
cat > PDLINPUT << EOF
FILE=${HPSS_HOME}/dst/ww98.1.dst
EOF

# run the executable
./myprogram.exe

results in:

 PHDST 3.13/01               IHEP/Protvino team              
 Compiled 990712.2145  Today is 990714.1419

  "FILE=hpsssrv1:/hpss/cern.ch/user/v/vaneldik/dst/ww98.1.dst"

 PHDST. "delstage -M hpsssrv1:/hpss/cern.ch/u" -

 PHDST. "ser/v/vaneldik/dst/ww98.1.dst"
 Wed Jul 14 14:19:40 MET DST 1999 delstage -M hpsssrv1:/hpss/cern.ch/user/v/vaneldik/dst/ww98.1.dst
 Wed Jul 14 14:19:40 MET DST 1999: DELSTAGE - Calling stagein to stage the tape with WAIT option
 DELSTAGE: Files staged, return code = 0

ww98.1.dst
 PHDST. Open file hpsssrv1:/hpss/cern.ch/user/v/vaneldik/dst/ww98.1.dst
etc...

Group files

If you want to give write permission for your HPSS-files to other Delphi people, you should create an HPSS subdirectory with the -m option:

     rfmkdir -m 775 $HPSS_HOME/groupfiles

All Delphi people will be able to create (and delete!) files in this directory.
For more details: man rfmkdir.

Removing staged files

When you update a file in your HPSS home directory, you have to make sure that your remove this file from the disk server! If the old version of your file is staged in, it will not be replaced automatically with the new version! To avoid this confusion, just issue:

     delstage -C -M $HPSS_HOME/myfile.paw

when you update you file $HPSS_HOME/myfile.paw

Copying HPSS-files to/from non-CERN machines

Currently there is no mechanism to easily transfer HPSS-files to/from machines outside CERN. Direct ftp or rfcp is not possible.

We suggest the following scheme, using the large /tmp disk on dxplus (or lxplus, please note however that /tmp area on hpplus and rsplus is very small!):

rlogin dxplus

cd /tmp

rfcp ${HPSS_HOME}/myfile /tmp/myfile

use ftp to transfer the file back home

rm /tmp/myfile

WARNING!! Do not try to rfcp your HPSS file to an AFS area, like your $SCRATCH !!
This file transfer is most likely to fail:

   dxplus05 [13] rfcp ${HPSS_HOME}/myfile ${AFS_SCRATCH}/myfile
   rfio_readlist() : I/O error
   copyfile_hpss(): -1 bytes out of 12877824 transfered
   rfcp : I/O error

Problems

Currently, HPSS is being tested. It may happen that CERN decide not to use it for LHC data storage, and discontinue the project. Although the user files will not be lost, it may mean we will have to switch to another way of storing data. With $DELPHI_PAW, $CORE_SCRATCH, $AFS_SCRATCH, $SCRATCH_WEEK, pubarch, user tapes, ... we have quite enough possibilities already!

Avoid the use of shortcuts like ${HPSS_HOME}/../../p/pubxx when you want to stage other people's HPSS files. The resolving of this kind of names confuses the stager!

We (DELPHI support) do not have a lot of experience with this system ourselves. The recommendations made on this page reflect our knowledge, but it may well be that users will run into problems that we have not realized. Please give us feedback!

IT have developed a wrapper around the RFIO commands, called hsm.

As always, questions, complaints, remarks:
delphi-core@cern.ch