Light weight Disk Pool Manager status and plans

Jean-Philippe Baud, IT-GD, CERN

May 2005

CERN IT-GD

Disk Pool Manager aims

• Provide a solution for Tier-2s in LCG-2• This implies a few tens of Terabytes in 2005

• Focus on manageability• Easy to install• Easy to configure• Low effort for ongoing maintenance• Easy to add/remove resources

• Support for multiple physical partitions• On one or more disk server nodes

• Support for different space types – volatile and permanent

• Support for multiple replicas of hot files within the disk pools

CERN IT-GD

Manageability

• Few daemons to install• No central configuration files

• Disk nodes request to add themselves to the DPM• All states are kept in a DB (easy to restore after a crash)

• Easy to remove disks and partitions• Allows simple reconfiguration of the Disk Pools• Administrator can temporarily remove file systems from the

DPM if a disk has crashed and is being repaired• DPM automatically configures a file system as “unavailable”

when it is not contactable

CERN IT-GD

Features

• DPM access via different interfaces• Direct Socket interface• SRM v1• SRM v2 Basic• Also offer a large part of SRM v2 Advanced

• Global Space Reservation (next version)• Namespace operations• Permissions• Copy and Remote Get/Put (next version)

• Data Access• Gridftp, rfio (ROOTD, XROOTD could be easily added)

CERN IT-GD

Security

• GSI Authentication and Authorization• Mapping done from Client DN to uid/gid pair• Authorization done in terms of uid/gid• Ownership of files is stored in DPM catalog, while the

physical files on disk are owned by the DPM • Permissions implemented on files and directories

• Unix (user, group, other) permissions• POSIX ACLs (group and users)

• Propose to use SRM as interface to set the permissions in the Storage Elements (require v2.1 minimum with Directory and Permission methods)

• VOMS will be integrated • VOMS roles appear as a list of gids

CERN IT-GD

Architecture

• The Light Weight Disk Pool Manager consists of• The Disk Pool Manager with its configuration and request

DB• The Disk Pool Name Server• The SRM servers• The RFIOD and DPM-aware GsiFTP servers

• How many machines ?• DPM, DPNS, and SRM can be installed on the same one• RFIOD : on each disk server managed by the DPM• GsiFTP : on each disk server managed by the DPM

CERN IT-GD

Example: SRM put processing (1)

Data ServerGridftp Daemon

ClientDPM Daemon

SRM Daemon

1a. SRM Put

1b. Put intoRequest Database

1c. Return SRM RequestId

DPM Database

DPNS Daemon

Data ServerGridftp Daemon

Data ServerGridftp Daemon

CERN IT-GD

Example: SRM put processing (2)

2a. Get Request from Database

2d. Add TURL in Request

Database and Mark ‘Ready’

2c. Pick best Data Server to put data onto

Data ServerGridftp Daemon

Client

SRM Daemon

2b. Check permissions and add to NS

DPM Database

DPNS Daemon

Data ServerGridftp Daemon

Data ServerGridftp Daemon

2e.add to replica table and set status ‘Pending’

DPM Daemon

CERN IT-GD

Example: SRM put processing (3)

3a. SRM getRequestStatus

Data ServerGridftp Daemon

ClientDPM Daemon

SRM Daemon

3c. Return TURL

DPM Database

3b. Get TURL from Request

DPNS Daemon

Data ServerGridftp Daemon

Data ServerGridftp Daemon

CERN IT-GD

Example: SRM put processing (4)

Data ServerGridftp Daemon

Client

SRM Daemon DPM Database

DPNS Daemon

Data ServerGridftp Daemon

Data ServerGridftp Daemon

4a. SRM(v1) set ‘Running’

4b. Update status of request

DPM Daemon

CERN IT-GD

Example: SRM put processing (5)

Data ServerGridftp Daemon

ClientDPM Daemon

SRM Daemon

5. put file via Gridftp

DPM Database

DPNS Daemon

Data ServerGridftp Daemon

Data ServerGridftp Daemon

CERN IT-GD

Example: SRM put processing (6)

6c. Get filesize

Data ServerGridftp Daemon

Client

SRM Daemon DPM Database

DPNS Daemon

Data ServerGridftp Daemon

Data ServerGridftp Daemon

6a. SRM(v1) set Done 6e. Update status of request

6d. Update replica metadata(size/status/pintime)

6b. Notify ‘Done’

DPM Daemon

CERN IT-GD

Example: Pool definition

• dpm-addpool --pool Volatile --def_filesize 200M –def_pintime 600 --s_type V

• dpm-addfs --pool Volatile --server se001 --fs /data01• dpm-qryconf

• POOL Volatile DEFSIZE 200.00M GC_START_THRESH 0 GC_STOP_THRESH 0 DEFPINTIME 600 PUT_RETENP 86400 FSS_POLICY maxfreespace GC_POLICY lru RS_POLICY fifo GID 0 S_TYPE V

• CAPACITY 17.73G FREE 17.73G (100%)• se001 /data01 CAPACITY 17.73G FREE 17.73G (100.0%)

CERN IT-GD

Testing

• Test suites written by Gilbert Grosdidier (Orsay) and Jiri Kosina (Prague)• Functionality tests (120 sub-tests)• Stress tests (40 suites running in parallel)

• The tests were run from very early in the development cycle and were improved as soon as new functionality was available in the servers

• The test results were immediately taken into account for the code development

CERN IT-GD

Status

• DPM will be part of LCG 2.5.0 release but is available from now on for testing

CERN IT-GD

Documentation/Packaging/Installation

• Reference man pages provided for each method and each server

• Installation guide being written• The DPM is available as a tarball or as a set of RPMs

• DPM-server-mysql• DPM-name-server-mysql• DPM-srm-server-mysql• DPM-rfio-server• DPM-client• DPM-gridftp-server

• Installation scripts (Yaim) are also available

CERN IT-GD

Deployment

• Replacement of ‘Classic SE’• Only metadata operations needed (the data does not need

to be copied)

• Satisfies gLite requirement for SRM interface at Tier-2s