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IDE disk servers at CERN

IDE disk servers at CERN. Helge Meinhard / CERN-IT CERN OpenLab workshop 17 March 2003. Introduction. HEP computing in the past: mostly reading from, processing, and writing to (tape) files sequentially Mainframe era (until ~ 1995): single machine, CPUs, tape drives, little disk space

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IDE disk servers at CERN

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  1. IDE disk servers at CERN Helge Meinhard / CERN-IT CERN OpenLab workshop 17 March 2003

  2. Introduction • HEP computing in the past: mostly reading from, processing, and writing to (tape) files sequentially • Mainframe era (until ~ 1995): single machine, CPUs, tape drives, little disk space • In response to scaling problem, development of SHIFT architecture (early 1990s) • Scalable farm out of ‘commodity’ components • RISC CPUs (PowerPC, MIPS, Alpha, PA-RISC, Sparc) • SCSI disks

  3. SHIFT architecture Diskserver Batch and diskSMP Network- FDDI- Hippi- Myrinet- Ethernet Tapeserver Network- Ethernet Batchserver Interactiveserver

  4. PC batch nodes • 1995: First studies at CERN of PCs as batch nodes (Windows NT) • 1997 onwards: Rapidly growing interest in Linux (on IA32 only) • 1998/99: First production farms for interactive and batch services running Linux on PC hardware at CERN

  5. PC disk servers • 1997/98: Prototypes with SCSI disks • 1998/99: Prototypes with EIDE disks • Different IDE adapters • Not RAIDed • 1999/2000: First Jumbo servers (20 x 75 GB) put into production • 2001: First rack-mounted systems • 2002: 97 new servers (54 TB usable) • 2003: 1.3 TB usable in one server at 13 kCHF • Total usable capacity today: ~ 200 TB

  6. 1997: ~700 GB SCSI/Sparc

  7. 2000/2001: 750 GB PC/EIDE (1)

  8. 2000/2001: 750 GB PC/EIDE (2)

  9. 2002: 670 GB PC/EIDE 2 systems

  10. Disks only EIDE/PC SCSI/ RISC Complete systems

  11. Gross Usable

  12. Today’s servers: Specifications • 19” rackmount, IA32 processor(s), 1 GB, 2x80 GB system disks, GigE (1000BaseT), redundant power supplies • >500 GB usable space on data disks • Hardware RAID offering redundancy • Hot-swap disk trays • Performance requirements network – disk: • 50 MB/s reading from server @ 500 GB • 40 MB/s writing to server @ 500 GB • 5 years on-site warranty

  13. Lessons learnt • Capacity is not everything, for good performance need • CPU, memory, RAID cards • Good OS and application software • Network connectivity • Large number of spindles • Firmware of RAID controllers and disks critical • Redundancy (RAID) is a must, required performance possible only with mirroring (RAID 1) so far

  14. Outlook • Good price/performance has risen interest in other application domains at CERN • AFS and MS DFS servers • Web servers, mail servers • Software servers (Linux installation) • Data base servers (Oracle, Objectivity/DB) • Access pattern of physics analysis likely to change • Investigating different file systems (XFS), RAID 5 (in software), … • Architecture constantly being reviewed • Alternatives investigated: data disks scattered over large number of batch nodes; SAN

  15. Conclusion • Architecture of early 1990s still valid • May even carry us into LHC era… • Important improvements made • Price/performance • Reliability (RAID) • Will review architecture soon (2003) • New application areas • New access patterns for physics analysis

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