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HPSS User Access

From HLRS Platforms

General

Please be aware that HPSS is a Hierarchical Storage Management System (HSM) with tape storage included; certain characteristics differ from a disk usage. When transferring a file to the system via (p)ftp it is stored on the disk cache as first step. Later, the data is migrated to two copies on tape. When retrieving a file, it may happen that the file is not on the disk cache anymore and has to be recalled from tape storage. This can take a few minutes.

Best Practices

  • Do not store large numbers of files.
  • It is not recommended to recursively store directory structures.
  • Better tar small files to one larger archive. Tar can also be used to keep the directory structures.
  • HPSS is not meant as a backup system.
  • Pftp is preferred since it automatically choses the right Class of Service (CoS) and is much faster due to parallel streaming of data.

Access Methods

Parallel FTP

On LAKI and HAZELHEN, there is a Parallel FTP client available.

The advantage of Parallel FTP is a file transfer which makes use of several parallel network connections or at least several parallel I/O streams.

On LAKI and HAZELHEN, you have to load the module "hpss" first:

module load hpss


To start the client, you should specify the number of parallel streams. We recommend a setting of 4.

pftp_client -w 4 hpsscore 4021


When requested, please provide your username and password. The password is your general hww password (as you have it for HAZELHEN for example).

Note: For technical reasons a password change is valid on HPSS with a one day delay.


Compared to the ftp access, there is no setting for the class of service necessary as this is done automatically by the pftp_client.

Use the parallel pput and pget commands instead of the normal put and get.

More details of using ftp and pftp to access HPSS can be found in the official User's guide.

FTP

Initiate the ftp connection to HPSS using

ftp hpsscore.hww.de 4021


When requested, please provide your username and password. The password is your general hww password (as you have it for Hermit for example).

ftp will check the .netrc file in the user's home directory, where e.g. login information can be given and the the ftp command can be used in e.g. scripts without a password prompt (see ftp man pages). Be aware of security issues, if a password is stored in plain text in a .netrc file.

Note: For technical reasons a password change is valid on HPSS with a one day delay.


Class of Service

When putting files into HPSS you have to specify a so called class of service. The class of service depends on the file size. The following values are possible:

102: size < 500MB

122: 0.5GB < size < 8GB

132: size > 8GB

You have to specify the class of service for a file prior to moving the file into HPSS. Before the transfer, you have to specify at the ftp prompt:

site setcos <cos id>

The setting of the cos id is valid for all following file transfers.

Beside the setting of the class of service, this option works just like normal ftp.


Other Access Methods

Currently, there are no other access methods available. Especially, there is currently no access to HPSS available from outside the hww network. For a transfer of stored files to your home site, please move these files to a system within hww where you have scp or GridFTP access.

Further Information

The official user guide by IBM can be found here: http://www.hpss-collaboration.org/documents/hpss752/Users_Guide.pdf