Guidance on when to use a particular HPSS interface is provided below. In general, PFTP provides the best data transfer performance. NFS is the slowest interface, and should not be the interface of choice for large HPSS data transfers.
Conditions in which a user might elect to use FTP are:
Utilizes standard FTP interface - Users and applications familiar with FTP can access HPSS with the standard command set.
Supports files greater than 2 gigabytes - FTP supports file sizes up to 2**64.
Supports any FTP client platforms - FTP commands may be issued from any vendor nodes with an FTP interface. No specialized code is required.
Conditions in which a user might elect to use PFTP are:
Provides faster file transfers than FTP - PFTP is a better performer than FTP since it provides the capability to stripe data across multiple client data ports.
Supports files greater than 2 gigabytes - PFTP supports file sizes up to 2**64.
Supports partial file transfer - PFTP provides options on the pget and pput commands to perform partial file transfers. This would be beneficial to users who want to extract pieces of large files.
Conditions in which a user might elect to use HTAR are:
Allows for several small files to be viewed by HPSS as one large file. This is very desirable to users who store lots of small files since HPSS does not perform well with lots of small files.
Since HTAR creates an index file when an archive file is created, files can be extracted quickly without having to rumage through the entire archive file since the index file stores the locations of each entry and is much smaller than the archive file, therefore much quicker to search.
Since all of the archived file information is stored in the index file it is possible to view the contents of an archive file without having to stage the entrire archive file from tape storage to the disk cache.
Conditions in which a user might elect to use NFS are:
Provides standard system access - Files may be accessed and managed through standard system mechanisms without calling a special library or program to translate commands
Eliminates multiple file instances - he need to maintain multiple instances of a file can be eliminated since files remain on the NFS server.
Accesses limited to smaller files
Supports any NFS client platforms - NFS access is supported from any client nodes with an NFS V2 or V3 interface. No specialized code is required.