SLACVX cluster Usage Policy

In the past there has been some confusion surrounding the usage of the SLACVX cluster. To prevent a reoccurence of this situation we have formulated this usage policy.

VAX cluster description

Currently the SLACVX cluster consists of a 3-CPU ALphaServer 8400, six VAX 4000/90's, 2 Alpha 3000/400's and 4 Alpha 3000/600's, representing a total CPU power of about 1600 MIPS. In addition there are over 200 GBytes of disk space which can be accessed from any node, the majority of which is used for storage of SLD data (in the form of JAZZDATA files). Finally there are 10 silo drives dedicated to providing tape access to the VAX cluster. A batch system modelled after the SLACVM batch system distributes jobs evenly over all machines.

Interactive Usage

The VAX 4000's, SLDB1-B5 are best suited for interactive logins. You can log into them using either a dumb terminal or an x-terminal. An x-terminal is the prefered method of access (see the SLAC X-terminal white paper for useful ammunition to persuade your supervisor/funding agency to cough up some money for one.) Each of these machines has unlimited user licences, so you should not have any problems logging in.

Appropriate interactive uses of the SLDB machines include reading mail, compiling and testing programs and debugging. Running interactive jobs which require only a few minutes of CPU time or which need features which are only available interactively such as Midas or the SLD event display are examples of appropriate uses. Note: It is NOT appropriate to run analysis jobs interactively if they use more than a few of minutes of CPU time and do not require interactive access. All such jobs should be run in batch.

An automated system informs system adminstrators when users greedily consume to much interactive CPU time, and a list of how many times people have exceeded the limit is available on the web (the CPUHOGS page), so frequent abusers may find themselves shunned by their collaborators at the SLAC cafeteria!

The ALPHAS (SLDA1, and SLDA3-A5) are also available for user logins, but should not be used for general purpose use, especially for running many X processes. The reason for this is that the Alpha's use much more memory for user processes than the VAX 4000's, so are not so well suited for handling MANY user processes. However, for uses such as interactive data analysis they do have more UMPH, so this is considered an appropriate use of the ALPHA machines, as is compiling routines and building shareables.

Currently AlphaServer 8400 is reserved for batch use and interactive logins are not permitted.

Logging In

Logging in from a dumb terminal

From the SLAC MICOM switch log in by choosing class LAT. At the igate> prompt enter
C SLDB1     or 
C SLDB2     etc
You can then log on with your normal SLACVX userid and password (if you do not have a SLACVX account you must fill in a new user request form available from the SLAC Computer Center User desk).

Logging in from an X-terminal

If your x-terminal is configured correctly it should bring up a window which looks like this

If your x-terminal does not bring up a window that looks like this consult Ramon Berger. To connect to the SLDBn machines just choose the appropriate entry from the menu, then log in using your SLACVX userid and password. (If you do not have a SLACVX account you must fill in a new user request form available from the SLAC Computer Center User desk).

Currently there is no easy way to find out which machine is most heavily loaded, so just try to think randomly and pick a number from 1 to 5 when choosing which machine to log in to.

Usage issues

Disk Space

Disk space on the SLACVX cluster is split into several types:
User Space
SLD User space is normally on the DISK$SLD_USR0: (or $USR for short) disk. This is where people typically keep their PREPMORT files, MAIL files, etc. Disk space is controlled by the VAX disk quota system. If you need your disk quota increased contact Ramon Berger.
Scratch Space
Each user has a directory on the scratch disk, DISK$SLD_SCR0: (or $SCR for short). Most users have a quota of 100,000 blocks on this disk, although slightly larger quotas might be given in exceptional circumstances. This disk is normally used for keeping LOG files or large EXE files on. Warning: Files on the scratch disk over ten days old are automatically deleted each night.
Data disks
A number of disks are available for storing large JAZZDATA files:
The SLDDAT disk is used primarily for data and MC mini-dst's. To see what files are available try
                DIR SLDDAT:
or check the DATA and MC catalogues. Users do not have write access to this disk.
The OUTPUT$STAGE disk is intended for very short term storage of large (typically JAZZDATA) files. The principle use of the disk is for writing output datasets to, prior to running a separate job to copy the data to tape. There are no quotas on this disk, but only a finite sace available for all to share, so some degree of common sense must be excercised to avoid the wrath of your collaborators. Please delete files as soon as they are no longer needed. Warning: Files on the output$stage disk over five days old are automatically deleted each night.
Staging Area
Files on tapes can be automatically copied to disk using the SLD staging system, described under Tape and Staging Usage below.
A web page is available that allows you to check how much disk space is has been used on several of these disks, and who is using it.

Tape and Staging Usage

It is possible to read tapes on the SLACVX cluster directly from IDA using the standard OPENTAPE command. Commands for querying and modifying the SLD Tapes database are also available on the SLACVX cluster.

Since there are only approximately 10 tape drives available for the SLACVX cluster please be courteous in your usage of this resource. In particular do not submit jobs which use many tape drives, and do not submit many jobs to run concurrently if they use tape drives (you can use the /AFTER qualifier on the SUBMIT command to stagger your jobs). It is possible to access tape drives when running interactively, but this should only be used if absolutely necessary (for example to debug a program which only crashes when reading tape). Interactive access to tapes is no-longer allowed (except in exceptional circumstances) since the same result can now be achieved using the SLD Tape Staging System.

If you (or others) are likely to read the same tape several times it is much better to use the Tape Staging System to access your data. This causes the tape to be read once and copied to disk, and then all subsequent accesses to the tape will read the data directly from disk. To use the staging system just add the qualifier STAGE to your IDA OPENTAPE command, as documented in the Staging System Users Guide.

Reporting Problems

See the introduction to the SLACVX how-to-fix page for information on reporting software and hardware problems with the SLACVX cluster.
Tony Johnson
Last Updated: