The procfs tuneable parameter that is used to define the default HSM archive ID is cannot be set persistently using lctl conf_param or lctl set_param -P. This is by design and is in part because the "hsm" procfs subtree is not created unless and until the HSM feature is itself activated.

The parameter variable is: mdt.<fsname>-MDT*.hsm.archive_id

Please consider a mechanism whereby the system-wide default for the archive ID is stored persistently by the MGS, as it simplifies administration overhead and makes other features such as server failover behave more predictably.