The PoolManager supports a type of objects called
link groups. These link groups are
used by the SRM
SpaceManager to make reservations against
space. Each link group corresponds to a number of dCache
pools in the following way: A link group is a collection of
links and each link
points to a set of pools. Each link group knows about the
size of its available space, which is the sum of all sizes
of available space in all the pools included in this link
group.
To create a new link group login to the Admin Interface and
cd to the PoolManager.
(local) admin >cd PoolManager(PoolManager) admin >psu create linkGroup <linkgroup>(PoolManager) admin >psu addto linkGroup <linkgroup> <link>(PoolManager) admin >save
With save the changes will be saved to
the file
/var/lib/dcache/config/poolmanager.conf.
Note
You can also edit the file
/var/lib/dcache/config/poolmanager.conf
to create a new link group. Please make sure that it
already exists. Otherwise you will have to create it
first via the Admin Interface by
(PoolManager) admin >save
Edit the file
/var/lib/dcache/config/poolmanager.conf
psu create linkGroup <linkgroup> psu addto linkGroup <linkgroup> <link>
After editing this file you will have to restart the
domain which contains the PoolManager cell to apply
the changes.
Note
Administrators will have to take care, that no pool is present in more than one link group.
Properties of space
reservation. The dCache administrator can specify a
RetentionPolicy and
an AccessLatency for
the space reservation, where
RetentionPolicy describes the quality of
the storage service that will be provided for the data (files)
stored in this space reservation and
AccessLatency describes the availability of
this data.
A link group has five boolean properties called
replicaAllowed,
outputAllowed,
custodialAllowed,
onlineAllowed and
nearlineAllowed. The values of these
properties (true or
false) can be configured via the Admin
Interface or directly in the file
/var/lib/dcache/config/poolmanager.conf.
The link groups contained in a space reservation match the
RetentionPolicy and the
AccessLatency of the space reservation.
(PoolManager) admin >psu set linkGroup custodialAllowed <linkgroup> <true|false>(PoolManager) admin >psu set linkGroup outputAllowed <linkgroup> <true|false>(PoolManager) admin >psu set linkGroup replicaAllowed <linkgroup> <true|false>(PoolManager) admin >psu set linkGroup onlineAllowed <linkgroup> <true|false>(PoolManager) admin >psu set linkGroup nearlineAllowed <linkgroup> <true|false>
Moreover an attribute can be assigned to a link group.
(PoolManager) admin >psu set linkGroup attribute <linkgroup> <key>=<value>
Example:
(PoolManager) admin >psu set linkGroup attribute name-of-LinkGroup VO=dteam001(PoolManager) admin >psu set linkGroup attribute name-of-LinkGroup VO=cms001(PoolManager) admin >psu set linkGroup attribute name-of-LinkGroup HSM=osm
Note
Please note that that it is up to administrators that the link groups’ attributes are specified correctly.
For example dCache will not complain if the link group
that does not support tape backend will be declared as one
that supports custodial.