SAM SRM deficiencies
[Originally JIRA SAMDEV-59]
The SAM SRM stager is missing some features that can cause problems. This isn't necessarily an exhaustive list:
No sub directory creation - not implemented because dCache doesn't need it (plus I don't think SRMv1 provided any way to do this). BestMan and DPM do need this. Currently we have to create new subdirectories by hand, which means we can't split large numbers of files over multiple subdirectories since we don't know how many we need in advance. Ironically, dCache supposedly has the most problems with large numbers of files in a single directory.
No limit on the number of external gridftp transfers it can initiate at once. This can cause problems with overloading and exhausting the available file descriptors.
I believe the gridftp transfers it initiates are always single stream, which means performance can be slower than what is possible.
SRM to SRM transfers with BestMan sites as a source fail with "SRM_NOT_SUPPORTED explanation=Gateway mode does not support this function". I don't know exactly what function it's objecting to.
Unlike the disk stager, there's no mechanism for synching the disk contents with the DB. Failed transfers can cause space consumption issues, since there can be a file taking up space that isn't in the DB, so isn't in the station's calculation of how much space is available. Supposedly srmls can have poor performance, which could be a problem for changing this.