In order to enable the SRM SpaceManager you need to add
the spacemanager service to your layout file
[<srm-${host.name}Domain>]
[<srm-${host.name}Domain>/srm]
[<srm-${host.name}Domain>/spacemanager]
and add (uncomment) the following definition in the file
/etc/dcache/dcache.conf
srmSpaceManagerEnabled=yes
Each SRM space reservation is made against the total
available disk space of a particular link group. If
dCache is configured correctly each byte of disk space,
that can be reserved, belongs to one and only one link
group. See the section called “SpaceManager configuration for Explicit Space Reservations” for a detailed
description.
Important
Make sure that no pool belongs to more than one pool group, no pool group belongs to more than one link and no link belongs to more than one link group.
If a space reservation is specified, the file will be stored in it (assuming the user has permission to do so in the name space).
Files written into a space made within a particular link group will end up on one of the pools belonging to this link group. The difference between the link group’s available space and the sum of all the current space reservation sizes is the available space in the link group.
The total space in dCache that can be reserved is the sum of the available spaces of all link groups.
dCache can perform implicit space reservations for
non-SRM transfers, SRM Version 1 transfers and
for SRM Version 2.2 data transfers that are not given
the space token explicitly. The parameter that enables
this behavior is
srmImplicitSpaceManagerEnabled, which
is described in the section called “SRM configuration for experts”.
If no implicit space reservation can be made, the transfer
will fail.
In case of SRM version 1.1 data transfers, when the
access latency and retention policy cannot be specified,
and in case of SRM V2.2 clients, when the access latency
and retention policy are not specified, the default values
will be used. First SRM will attempt to use the values
of AccessLatency and
RetentionPolicy tags from the directory
to which a file is being written. If the tags are present,
then the AccessLatency and
RetentionPolicy will be set on basis of
the system wide defaults, which are controlled by
DefaultRetentionPolicy and
DefaultAccessLatencyForSpaceReservation
variables in
/etc/dcache/dcache.conf.
You can check if the AccessLatency and
RetentionPolicy tags are present by
using the following commands:
[root] #/usr/bin/chimera-cli lstag /path/to/directoryTotal: numberOfTags tag1 tag2 .. AccessLatency RetentionPolicy
If the output contains the lines
AccessLatency and
RetentionPolicy then the tags are
already present and you can get the actual values of these
tags by executing the following commands, which are shown
together with example outputs:
Example:
[root] #/usr/bin/chimera-cli readtag /data/experiment-a AccessLatencyONLINE[root] #/usr/bin/chimera-cli readtag /data/experiment-a RetentionPolicyCUSTODIAL
The valid AccessLatency values are
ONLINE and NEARLINE,
valid RetentionPolicy values are
REPLICA and
CUSTODIAL.
To create/change the values of the tags, please execute :
[root] #/usr/bin/chimera-cli writetag /path/to/directory AccessLatency "<New AccessLatency>"[root] #/usr/bin/chimera-cli writetag /path/to/directory RetentionPolicy "<New RetentionPolicy>"
Note
Some clients also have default values, which are used when not explicitly specified by the user. I this case server side defaults will have no effect.
Note
If the implicit space reservation is not enabled the pools in the link groups will be excluded from consideration and only the remaining pools will be considered for storing the incoming data, and classical pool selection mechanism will be used.