1 / 24

The Next Generation Root File Server

The Next Generation Root File Server. Andrew Hanushevsky Stanford Linear Accelerator Center 27-September-2004 http://xrootd.slac.stanford.edu. What is xrootd?. File Server Provides high performance file-based access Scalable, extensible, naively usable Fault tolerant

radley
Télécharger la présentation

The Next Generation Root File Server

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Next Generation Root File Server Andrew Hanushevsky Stanford Linear Accelerator Center 27-September-2004 http://xrootd.slac.stanford.edu

  2. What is xrootd? • File Server • Provides high performance file-based access • Scalable, extensible, naively usable • Fault tolerant • Server failures handled in a natural way • Servers may be dynamically added and removed • Secure • Framework allows use of almost any protocol • Rootd Compatible 2: xrootd

  3. Goals II • Simplicity • Can run xrootd out of the box • No config file needed for non-complicated/small installations • Generality • Can configure xrootd for ultimate performance • Meant for intermediate to large-scale sites 3: xrootd

  4. How Is high performance achieved? • Rich but efficient server protocol • Combines file serving with P2P elements • Allows client hints for improved performance • Pre-read, prepare, client access & processing hints, • Multiplexed request stream • Multiple parallel requests allowed per client • An extensible base architecture • Heavily multi-threaded • Clients are dedicated threads whenever possible • Extensive use of OS I/O features • Async I/O, device polling, etc. • Load adaptive reconfiguration. 4: xrootd

  5. xrootd Server Architecture p2p heart application Protocol & Thread Manager xrd xrootd Protocol Layer xroot Authentication Filesystem Logical Layer ofs odc Authorization optional Filesystem Physical Layer oss (included in distribution) Filesystem Implementation _fs mss 5: xrootd

  6. Rootd Bilateral Compatibility Client-Side Compatibility Application TXNetFile xrootd rootd TNetFile Server-Side Compatibility Application rootd xrootd rootd compability TNetFile client 6: xrootd

  7. How performant is it? • Can deliver data at disk speeds (streaming mode) • Assuming good network & proper TCP buffer size • Low CPU overhead • 75% less CPU than NFS for same data load • It is memory hungry, however. • General requirements • Middling speed machine • The more CPU’s the better • 1-2GB of RAM 7: xrootd

  8. How is scalability achieved? • Protocol allows server scalability • Server directed I/O segmenting • Request deferral to pace client load • Unsolicited responses for ad hoc client steering • P2P elements for lashing servers together • Request redirection key element • Integrated with a P2P control network • olbd servers provide control information 8: xrootd

  9. How does it scale? • xrootd scales in multiple dimensions • Can run multiple load balanced xrootd’s • Provides single uniform name and data space • Scales from 1 to over 32,000 cooperating data servers • Architected as self-configuring structured peer-to-peer (SP2) data servers • Servers can be added & removed at any time • Client (TXNetFile) understands SP2 configurations • xrootd informs client when running in this mode • Client has more recovery options in the event of failure 9: xrootd

  10. Load Balancing Implementation • Control Interface (olbd) • Load balancing meta operations • Find files, change status, forwarded requests • Data Interface (xrootd) • Data is provided to clients • Interfaces to olbd via the ofs layer • Separation is important • Allows use of any protocol • Client need not know the control protocol 10: xrootd

  11. data Entities & Relationships xrootd Data Network (redirectors steer clients to data Data servers provide data) olbd Control Network Managers & Servers (resource info, file location) Redirectors olbd M ctl xrootd olbd S Data Clients xrootd Data Servers 11: xrootd

  12. ufs ufs Typical SP2 Configuration subscribe olbd xrootd Dynamic Selection olbd xrootd mss client redirector xrootd subscribe olbd 12: xrootd

  13. Example: SLAC Configuration kan01 kan02 kan03 kan04 kanxx kanolb-a bbr-olb03 bbr-olb04 client machines 13: xrootd

  14. Why do this? • Can transparently & incrementally scale • Servers can come and go • Load balancing effects recovery • New servers can be added at any time • Servers may be brought down for maintenance • Files can be moved around in real-time • Client simply adjust to the new configuration • TXNetFile object handles recovery protocol 14: xrootd

  15. What we have seen • For a single server: • 1,000 simultaneous clients • 2,200 simultaneous open files • Bottlenecks • Disk I/O (memory next behind) 15: xrootd

  16. What Have We Heard • The system is too stable • Users run extra-long jobs (1-2 weeks) now • Error not discovered until weeks later • The system is too aggressive • New servers are immediately taken over • Easy configuration but startling for administrators 16: xrootd

  17. Next: Getting remote data SLAC Firewall Firewall Firewall IN2P3 RAL IN2P3proxy RALproxy xrootd’s Firewalls require Proxy servers 17: xrootd

  18. Proxy Service • Attempts to address competing goals • Security • Deal with firewalls • Scalability • Administrative • Configuration • Performance • Ad hoc forwarding for near-zero wait time • Intelligent caching in local domain 18: xrootd

  19. Proxy Implementation • Uses capabilities of olbd and xrootd • Simply an extension of local load balancing • Implemented as a special file system type • Interfaces in the ofs layer • Functions in the oss layer • Primary developer is Heinz Stockinger 19: xrootd

  20. Proxy Interactions data01 data02 data03 data04 RAL local olb proxy olb 4 5 local olb proxy olb SLAC 3 1 red01 data02 data03 proxy01 2 client machines 20: xrootd

  21. Why This Arrangement? • Minimizes cross-domain knowledge • Necessary for scalability in all areas • Security • Configuration • Fault tolerance & recovery 21: xrootd

  22. 2 3 2 1 Scalable Proxy Security SLAC PROXY OLBD RAL PROXY OLBD Data Servers Data Servers Firewall 1 Authenticate & develop session key 2 Distribute session key to authenticated subscribers 3 Data servers can log into each other using session key 22: xrootd

  23. Proxy Performance • Introduces minimal latency overhead • Virtually undetectably from US/Europe • Negligible on faster links • 2% slower on fast US/US links • 10% slower on LAN • Can be further improved • Parallel streams • Better window size calculation • Asynchronous I/O 23: xrootd

  24. Conclusion • xrootd provides high performance file access • Unique performance, usability, scalability, security, compatibility, and recoverability characteristics • Should scale to tens of thousand clients • Can support tens of thousand of servers • Distributed as part of the CERN root package • Open software, supported by • SLAC (server) and INFN-Padova (client) 24: xrootd

More Related