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dCache Nearline Storage Driver for CTA

This is nearline storage plugin for dCache.

DOI

To compile the plugin, run:

mvn package

This produces a tarball in the target directory containing the plugin.

Using the plugin with dCache

To use this plugin with dCache, place the directory containing this file in /usr/local/share/dcache/plugins/ on a dCache pool. Restart the pool to load the plugin.

To verify that the plugin is loaded, navigate to the pool in the dCache admin shell and issue the command:

hsm show providers

The plugin should be listed as dcache-cta.

To activate the plugin, create an HSM instance using:

hsm create osm name dcache-cta [-key=value]...

example:

hsm create osm cta dcache-cta -cta-user=userA \
     -cta-group=groupA -cta-instance-name=instanceA \
     -cta-frontend-addr=cta-forntend-host:17017 \
     -cta-use-tls=true \
     -io-endpoint=a.b.c.d -io-port=1094

The dCache files stored in CTA will have hsm uri in form

<hsmType>://<hsmName>/<pnfsid>?arichiveid=<id>

Where id represents the CTA internal archiveId

for example:

osm://cta/00001D43C0C086CA459298C634D67F68AB6B?archiveid=8402

In the CTA catalog the dCache's pnfsids are referenced as disk_file_id field:

db => select * from archive_file where disk_file_id = '00001D43C0C086CA459298C634D67F68AB6B';
-[ RECORD 1 ]-------+-------------------------------------
archive_file_id     | 8402
disk_instance_name  | instanceA
disk_file_id        | 00001D43C0C086CA459298C634D67F68AB6B
disk_file_uid       | 1
disk_file_gid       | 1
size_in_bytes       | 10482
checksum_blob       | \x0a08080112043309f498
checksum_adler32    | 2566129971
storage_class_id    | 81
creation_time       | 1635150624
reconciliation_time | 1635150624
is_deleted          | 0
collocation_hint    |

NOTE: dCache-CTA driver doesn't preserve file's ownership, thus values of uid and gid fields contain arbitrary values.

dCache pool configuration

As CTA has its own scheduler and flush/restore queue the dCache pools should be configured to submit as much request as possible. Thus grouping and collecting request on the pool side should be disabled:

queue define class -expire=0 -pending=0 -total=0 -open <hsmType> *

The available configuration options:

Name Description required default
cta-instance-name The dCache instance name configured in CTA yes -
cta-frontend-addr The CTA cta-dcache endpoint yes -
cta-user The dCache instance associated user in CTA yes -
cta-group The dCache instance associated group in CTA yes -
cta-ca-chain The path to CA root chain for use with TLS no -
cta-use-tls A switch (true/false) to enable TLS for CTA control connection no false
cta-frontend-timeout How log dCache waits in seconds for CTA frontend to reply no 30
io-endpoint The hostname or IP offered by dCache for IO by CTA no hostname
io-port The TCP port offered by dCache for IO by CTA no -
restore-success-on-close obsolete - -

Acknowledgements

This driver is based and inspired by cta-communicator by Lea Morschel and sapphire by Svenja Meyer