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Filesystem Layouts and Apache Performance

Filesystem Layouts and Apache Performance. Jeff D. Almeida spud@spudzeppelin.com. Foreword. Convention used throughout:

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Filesystem Layouts and Apache Performance

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  1. Filesystem Layouts and Apache Performance • Jeff D. Almeida • spud@spudzeppelin.com

  2. Foreword • Convention used throughout: • Our sample site is “puppysurprise.com”, a hypothetical advertiser-supported content site where professional football players share their favorite dog stories from each year of their careers. • Acknowledgements/Apologies-in-advance: • Dean Gaudet • Christopher Alexander • The Grateful Dead

  3. The Proposition • System Administrators can directly impact how their webservers perform by decisions they make when initially configuring systems. 1

  4. The Mission • Teach system administrators about “best practices” for system installations that lead to optimum performance. • Enable system administrators to make informed decisions regarding trade-offs among performance and other constraints (e.g. security, multiple users, available hardware). 2

  5. The Destination • Apache webservers on optimally configured hardware. • Apache performing at its best. • Hardware not taxed unnecessarily. 3

  6. The Origin • Default installation for Apache is suboptimal. • Many vendor-provided installs are even worse. • Default/”standard” hardware configurations exacerbate the problem. • Many times, site design decisions contribute as well. 4

  7. A Long, Strange Trip • Until “recently” performance wasn’t much of a consideration. • Old. proven ways of thinking among Unix admins. • Resulting DocumentRoot: • /usr/local/apache/htdocs • /usr/local/web/sites/puppysurprise/docs • /var/web/puppysurprise/docs 5

  8. Vendor Paradox • In theory, not selling high-performance webservers. • In practice, web services have been the “killer app” for Linux, FreeBSD, etc. • A lot of this appears to be whimsy. Resulting DocumentRoot: • /home/httpd/sites/puppysurprise/docs • /usr/share/webdocs/puppysurprise • /usr/users/httpd/htdocs

  9. Hardware Vendors • Old guard, traditional Unix vendors slowest to adapt. • High-density rackmount Intel/Linux vendors doing better. • Webservers are their bread-and-butter • Problems arise from the disk configuration.

  10. Site Design Problems • Traditional thinking favors “deep” websites. • /teams/1997/Pats/qbs/Drew_Bledsoe/index.html • Traditional thinking favors designer-configurable access controls • .htaccess files

  11. The Timeless Way of Building Webservers • Optimized hardware configuration • Optimized filesystem layouts • Optimized Apache configuration • Optimized website design 6

  12. Patterns for Successful Server Design • Not a “one-size-fits-all” sort of solution • Different environments and requirements call for different solutions • Learn to make installation-time decisions that optimize aspects of server configuration. • Patterns are manifestations of “the way”. 7

  13. Hardware Optimizations I • Avoiding Device Contention • Three things looking for disk seeks: docs, logs, swap • In order of decreasing efficiency, keep the three on separate: • Buses (unlikely on Intel hardware) • Controllers • Channels • Spindles • Partitions • Avoid clutter to speed seeks

  14. Hardware Optimizations II • Make the right purchasing decisions • Enough RAM to never swap • Disks and controllers • Hardware RAID 0+1 • Lesson from the database gurus • Smooth out spikes • Superior to Software RAID, RAID 5 • SCSI not IDE • SCSI is non-blocking

  15. Filesystem Layouts I • Understand the way Apache opens files for reading • Not a bug, actually proper behavior • Example: • Docroot /usr/local/web/sites/puppysurprise/docs • File /teams/1997/Pats/qbs/Drew_Bledsoe/index.html • 12 layers of parent directories!

  16. Filesystem Layouts II • Based on this, put our docroot at /puppysurprise • Why not? Worst case, it’s on a separate partition anyway at this point, right?

  17. Apache Configuration I • We’re focusing on those performance-tuning tips that are filesystem-specific. Plenty of others exist. • Options +FollowSymLinks • AllowOverride None • Don’t use suexec (or UserDir at all, if possible)

  18. Apache Configuration II • Can you afford to log in some other fashion? • Unless docs and logs are on separate buses, there’s always going to be some contention. • Logging options: • disable it altogether • buffered logging • remote syslog • remote database • conjectures: named pipe? netpipe?

  19. Site Design • Performance favors the horizontal • Let the sysadmin set the access controls in httpd.conf • Akamai? Or at least Aka-me?

  20. Conclusions • File /puppysurprise/97Pats/Drew_Bledsoe.html is in a performance-optimized location. • Putting /puppysurprise/ on it’s own RAID 0+1 controller is a hardware performance optimization. • Server logs are on their own partition (at worst) or another machine altogether.

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