1. NorduGrid and LCG middleware comparison
ARC vs LCG2
NorduGrid and LCG middleware comparison
Oxana Smirnova
Lund/ATLAS
August 2, 2004, CERN

2. Setting the field NorduGrid LCG Name at birth
Nordic Testbed for Wide Area Computing and Data Handling
Large Hadron Collider Computing Grid
When
Started in spring 2001
Started in spring 2002
Who
Nordic universities: ATLAS teams, others
CERN: IT division and LHC experiments
Members and associates
Dozens
Hundreds
Why
Provide researchers with adequate computing power by harnessing distributed resources using Grid technologies

3. Main activity areas NorduGrid LCG
Nordic countries Certificate Authority
Grid middleware (Advanced Resource Connector, ARC) development
Applications support (mainly ATLAS)
Support of resources (those in the universities)
User support
Grid deployment (over the available resources)
includes user and applications support
Grid Middleware (took over from EDG, collaboration with EGEE )
Applications (GEANT4, POOL, generators,…)
Distributed Analysis
Fabric and networking (mainly CERN, regional centers)

4. Basic systems and services (figures from the NG Monitor and GridIce)
NorduGrid
LCG
Computing resources
Standalone stations, Linux clusters, pools, other UN*X systems
PBS, SGE, Condor,…
All shared
~40 sites
Linux (RH7.3, soon: Scientific Linux) clusters
PBS, LSF
Some shared
~70 sites
Storage resources
Disk storage
~30 TB
Disk and tape storage
~40 TB
Certification
Resources and users must be certified by a CA authorized by the common Security Team
Resource management
Up to resource owners
Centrally coordinated
User management
~500 users
Centralized, VO-based
? Users ?
SWEGRID computers count towards both; deploy only ARC so far

5. Relation to Middleware
NorduGrid
LCG
Started deploying EDG middleware in 2001
Started deploying EDG middleware in 2002
Started developing own middleware (ARC) in February 2002
Reason: EDG m/w could not support ATLAS DC1 production
Tailored EDG middleware (LCG1 and LCG2)
Reason: EDG m/w could not support Data Challenges by LHC experiments
Uses ARC for production
Satisfactory performance for ATLAS DC2, CMS (in Estonia), all kinds of Nordic researchers
Uses LCG2 for Data Challenges
Not quite satisfactory performance so far
Will continue developing ARC, no need to switch to anything else
willing to offer ARC to LCG
Will develop and deploy gLite, together with EGEE
EGEE requires Nordic sites to run LCG2/gLite

6. Middleware: general ARC LCG2 License GPL EDG Platforms
GNU Linux (runs on RH*, SuSE*, Mandrake*, Debian3.0 etc), tests on Mac OS X (GT2 issues)
RedHat 7.3, in future: Scientific Linux, Mac OS X
Grid middleware
Globus 2.4.3, own patches
Globus 2.2.4, patches by VDT
GT3 RLS
EDG RLS
GACL -
GSOAP
- (?)
Condor-G
EDG VOMS
Core developers
6 ± 2
Some dozens ?

7. ARChitecture
Goal: no single point of failure

8. ARC-Geography

9. Components overview (1/2)
ARC
LCG2
Computing element
Grid Manager: resides on a master node
Interface to LRMS
Input data stage-in (LFN resolution etc)
Output data stage-out and eventual registration
Job management (kill, restart, logging, clean up etc)
Pluggable (e.g. accounting plug-in, benchmarking...)
Provides info for infosystem (stateful)
CE: resides on a master node
Includes some data management tools (not integrated)
Storage element
« Simple »: stripped down computing element (gridftp server + GACL)
« Smart »:
Reliable file transfer
Communication with various data indexing services
Asynchronous data manipulation
« Classic »: gridftp server
« SE »: SRM-enabled

10. Components overview (2/2)
ARC
LCG2
Worker node
Not needed
Resides at every WN; mostly data management functionality
User Interface
A lightweigt client
Security: certificate request, proxy...
Job submission: matchmaking, scheduling, upload
Job management: monitor, kill, proxy renewal etc
Grid file movement: copy/erase/register etc
Central service
Job submission: RB contact
Job management: monitor, kill etc
GIIS
Part of the Computing Element service (« server » package)
Separate service (BDII)
Resource Broker
Not needed (UI’s functionality)
Job submission: matchmaking, scheduling, sandbox transfer, logging

11. Information System: MDS
ARC
LCG2
LDAP tree
Own
Cluster-oriented
Glue
LDAP schema
GRIS
At each cluster and SE
GIIS
No data caching
Strict hierarchical system (Grid - Country or an international body - National body - Cluster)
Multi-rooted at top and for big countries
Caching on
Some hierarchy
Top-level GIISes replaced by BDII
Clients
Broker/User Interface
Monitor
Broker

12. No caching, only registrants lists
ARC MDS details
No caching, only registrants lists
Cluster sub-tree

13. Grid workload management
ARC
LCG2
Job description
Globus RSL + extensions
JDL: Condor classAds
User Interface (UI)
Local to user or shared, unlimited amount (unknown, often several per user)
Typically shared, several per testbed
Matchmaking, scheduling
Decentralized (local to every client), integrated into UI, relies on Infosys
Dedicated Resource Broker (RB), approx. one per VO, relies on infosys
Job description transaction
UI uploads files directly to chosen clusters
Sandbox is transferred via RB
Job monitoring, management
Direct queries to clusters
Queries via the submission RB

14. Grid data management ARC LCG2 Replica services
Replica Catalog (Globus + patches), RLS (Globus)
RLS (EDG)
Input data
LFN or URL defined in job description, staged by the server, cached
If LFN or GUID is defined in job description, the job is steered to the location; otherwise files must be moved by the job (hence necessary to install LCG2 on every worker node)
Output data
LFN or URL defined in job description, uploaded and registered by the server
FN (+LFN +SE) specified in job description, uploaded by the server
Automatic, bulk replication
Not supported (yet?)

15. User management ARC LCG2 VO membership Several options: LDAP servers
VOMS
Plain text lists (served by HTTP)
VO-based functionality -
Local user mapping
Resource availability
Tags publishing
Databases
Monitoring

16. Other services ARC LCG2 Monitoring
Based entirely on Information System, no special sensors
Uses additional sensors apart of GRISes
Bookkeeping
Under development (user-friendly interface is missing), Web-service
Part of the WMS
Distribution
Available via FTP and Web: nightly snapshots, weekly tags, stable releases (RPM, tgz)
Available via anonymous CVS checkout, LCFG (RPM)
Support
Web site, support ticket system, Bugzilla, discussion mailing list
Web site (!), support ticket system (?), Savannah (?), plenty of mailing lists

17. Summary
A major difference: ARC concentrates most job and data management functionality in the cluster front-end (the Grid Manager)
LCG2 requires installation on each WN; ARC does not
Another major difference: Information System
Wrong/outdated/insufficient information is the most destructive thing on Earth
Another difference: ARC is oriented towards particular persons and small teams, while LCG2 is for large organizations
ARC has a lightweight client, LCG2 has none
ARC user can monitor each job on the Web, LCG can not
ARC is portable to many systems, LCG is not
LCG has tape storage facilities, NorduGrid has none
LCG has common policies, NorduGrid has none
Plenty of other differences, but many commonalities as well
Certification
Absence of a reliable accounting system
No fine-grained information access
Ultimately, the common goal – to help them physicists to find the Higgs 