BeStMan-Xrootd: SRM v2.2 Load Balancing Frontend for GridFTP Servers

1. BeStMan-Xrootd Alex Sim Computational Research Division Lawrence Berkeley National Laboratory

2. BeStMan-Xrootd • Current version 2.2.0.7 (Jan. 9, 2008) • Implementation of SRM v2.2 for Xrootd • Designed to work with gLite File Transfer Service (FTS) and glite-url-copy • Generic SRM v2.2 load balancing frontend for GridFTP servers • Support for subset of SRM v2.2 interfaces • srmPing, srmLs, srmRm, srmMkdir, srmRmdir, srmPrepareToPut (Status, PutDone), srmPrepareToGet (Status, ReleaseFiles) • Use of existing gridftp file transfer services • Support for multiple file transfer servers • Can be used with any storage systems • that have a GridFTP server and a POSIX file system interface • Simple installation and maintenance

3. How it works all together in Put/Get Client GridFTP file transfers TURL srmPrepareToGet/Put srmReleaseFiles/srmPutDone BeStMan-Xrootd Xrootd Gridftp server Gridftp server Gridftp server XrootdFS . . .

4. How it works all together in Ls/Rm/Mkdir/Rmdir Client srmLs/srmRm/srmMkdir/srmRmdir BeStMan-Xrootd Xrootd Gridftp server Gridftp server Gridftp server XrootdFS . . .

5. Interoperability with other SRM v2.2 CASTOR dCache Disk DPM BeStMan mySQL DB BNL SLAC LBNL xrootd Client User/application SRB(iRODS) SDSC SINICA LBNL EGEE

6. Test results • All stress tests done by Wei Yang at SLAC • Preparation • BeStMan-xrootd and XrootdFS on dual dual-core AMD Opteron 275, 2.2Ghz, 4GB memory, 1Gbit NIC • GridFTP • osgserv01,04 on dual AMD Opteron 244 1.8Ghz (total two cores), 2GB memory, 1 Gbit NIC • griddev05,6,7 on dual Intel Pentium III 866Mhz, 1GB memory, 100Mbit NIC • Job submission on lxplus202.cern.ch • glite-url-copy was used to simulate FTS • On average, lxplus can run 100 glite-url-copy for PtP in 16.4 seconds and 100 PtG in 14.3 seconds • A script contains glite-url-copy from lxplus.cern.ch to run

7. Test results for srmPrepareToPut • File is put into a non-existing directory • GridFTP server creates the file and directory. • 500 PtP, no pause • All completed. • 1000 PtP, no pause • All completed. • 5000 PtP, sleep 5 seconds for every 50 PtP • All completed.

8. Test results for srmPrepareToGet • 500 PtG, no pause • All completed. • 1000 PtG, no pause • 980 completed • 20 GridFTP error or timeout. • 5000 PtG, sleep 5 seconds for every 200 PtG • 4947 completed • 53 GridFTP error or timeout. • Note: GridFTP error or timeout can be ignored • Because they happened at a stage after the glite-url-copy has finished PtG exchange with BeStMan-Xrootd.

9. Additional tests • In the test above, we saw a performance gap between PUT and GET • So we configured two additional GridFTP servers (the 'osgserv' class machine) • Did a few tests again • All other testing environment remained the same.

10. Test results for additional tests • Test result for srmPrepareToPut • 5000 PtP, no pause, all completed : Total 885 seconds (~ 5.6PtP/sec). • Test result for srmPrepareToGet • 5000 PtG, no pause. all completed : Total 709 seconds (~ 7 PtG/sec). • Note: The reason of PtP and PtG performance gap was that Xrootd storage imposes a 5 seconds delay when creating new files. • So the GridFTP servers may be overrun by the incoming PtP requests, which in turn caused large number of glite-url-copy processes accumulated at the submission host

11. Conclusion • BeStMan-Xrootd gives an SRM v2.2 access to the Xrootd • It works with all generic srm client tools as well as FTS file transfers. • This work can be applied to other Xrootd-like systems that would need SRM v2.2 layer

12. Documents and Support • BeStMan-Xrootd • http://wt2.slac.stanford.edu/xrootdfs/bestman-xrootd.html • http://datagrid.lbl.gov/bestman • Xrootd • http://confluence.slac.stanford.edu/display/ds/Xrootd • SRM Collaboration and SRM Specifications • http://sdm.lbl.gov/srm-wg • Contact and support : srm@lbl.gov