Download - AFS Update
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IT/PDP/DM Section
• Section leader : H.Renshall, O.Barring
• Tape infrastructure unit led by C.Curran
– F.Collin, R.Minchin
• SHIFT and CASTOR software unit led by J-P. Baud
– O.Barring, J-D.Durand
• Commercial products services (HPPS and AFS) unit led by H.Renshall
– B.Antoine, D.Asbury, O.Le Moigne
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AFS dependencies
• server hardware/OS
• AFS server process
• Network
• AFS client software (cache manager)
• client hardware/OS
• application
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AFS hardware
• 33 servers– 9 IBM (AIX)– 7 SUNs (Solaris)– 17 PCs (Solaris, Linux)
• disk space : 2TB available– user : 600 GB used / 1100 GB alloc– project : 800 GB used / 1400 GB alloc
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Disk policy
• Home directories (managed by xspaceadm)– limited to 300 MB/user– mirror or RAID 5
• Project space (managed by afs_admin)– several 100GB/experiment– NO MIRROR or RAID 5 – backed up : if one disk fails, data of the day before
will be recovered from tapes – or not backed up (scratch volumes : q.*)
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AFS software
• Current version : AFS 3.4a (UNIXes, NT)
• AFS 3.5– mainly for performance improvement– deployed only for Linux
• AFS 3.6 : beta under test– volumes > 2GB, Solaris 64 bits– will be deployed next year
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Cache Manager problems
• 2 problems :– Cache consistency : a modification is not
visible everywhere– Cache corruption : a file is corrupted
• Solution– fs flush/flushv discouraged– should be reported to [email protected]– new patch to be installed soon on HP nodes
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Other problems
• Performance– Overloaded servers (eg: ASIS volumes moved)– Backups
• Connectivity problem– specially with FDDI
• Servers crashes (need for supported config)
• Disk failures (need for redundancy)
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Replication
• Volumes can be read-only replicated on several servers– load balancing
– no trouble for clients if one server crashes
– good for everything that is accessed a lot and not modified often:
• binaries
• documentation
– give us proposal
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Linux
• Version certified by IT/DIS : Redhat 5.1 using old free client from MIT (AFS 3.3)– stability problems (specially on SMP)– lots of cache consistency/corruption problems– completely unsupported (no pb investigation)
• Supported version : Redhat 6.0, AFS 3.5 (Redhat 6.1 soon)
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Plans
• Update hardware : homogeneity/stability– SUN Solaris
• user : mirror or RAID 5• project : all in mirror or RAID 5 ?
– PC Linux : replica + scratch– Ethernet (100Mb/s or 1Gb/s)
• Update software– AFS 3.6 next year
• rethinking user workspace
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Contact
• User problem– Atlas group administrator (quota)– [email protected] and Atlas support list
• Administration problem– [email protected] and Atlas support list
• Info– http://consult.cern.ch/services/afs