LCA2012 – Wednesday Morning

A Tour of btrfs – Avi Miller

  • Now
  • All data and metadata is copy-on-write
  • CRC all metadata and data
  • Writable snapshots
  • multi-device support ( raid0 , raid1 , raid 10 )
  • online resize and defrag, online device replace
  • transparent compressions, efficient storage for small files
  • Soon
  • Fixes for perf and stability
  • background scrubbing, LZO compression, batched discard, file defrag options, per-inode flags
  • Larger block sizes for ( especially for metadata, to provide perf improvements in some cases)
  • Scrubbing uses CRC to varify data on disk, fixes bad ones with good copy on another disk which has okay CRC
  • “df ” gives completely wrong values on how full the disk is or it’s size
  • discard/trim supported both real time and batched
  • Drive Swapping – current raid rebuilds via balance code, can also restripe between RAID levels
  • btrs send/receive in development
  • Embedded – friendly to small machines, not as friendly to small disks (being worked on) Works well with low-end flash drives
  • RAID 5/6 – MErge pending completion of fsck work. will also add triple mirroring
  • beta read-only filesystem recovery tool – copies data out of corrupt FS
  • tree root-history log lets us recovery from many hardware errors. “mount -recover”
  • New fsck release on the way. May be announced very soon
  • yum-plugin-fs-snapshot . yum plug to trigger a snapshot on package install/upgrades

 

The Web as an application development platform – Shane Stephens and Mike Lawther

  • When and how to move from native to web/cloud apps
  • Examples
  • Text based like email (pine, mutt, outlook). 15 years ago web-based email started. access anywhere, no install required, easy to start using, use anywhere
  • Desktop publishing. Hard to collaborate with other people using desktop based software by emailing docs around to other people. On the web it’s often native multi-user. Send Links rather than emailing whole doc.
  • On web everybody always running latest version
  • Github gives you one-stop shop for projects. wiki, forums etc. Native in app rather than bolt on to desktop version
  • Graphics
  • Flickr – has native sharing, backups etc
  • Online editing of images etc now possible
  • Games
  • Farmville – no install, easy to share links
  • Angry Birds – has web version, html5 , flash for sound, 60fps
  • Not at stage where First person shooters going to happen yet. Users have high end hardware
  • Overall Benefits – No install, universal access to data, always using latest version, collaboration and sharing built in. Simple text layout, Web as IDE, open and modular enviroment
  • Drawbacks – Layout more involved than desktops apps, distributed code makes debugging hard, cross browser compatibility, security limits flexibility.
  • Useful web technologies (see also HTML5Rocks website) :
  • Display / Rendering
  • HTML , SVG , Canvas – All fairly easy to combine
  • WebGL , flexbox and grid <- future
  • Communications
  • Standard http requests, AJAX / XHR , Websockets / Browser Channel , libraries like Faye etc
  • Storage
  • Traditionally just cookies, Session Storage, Local Storage, indexDb, AppCache
  • Environment Enhancements
  • jQuery , CoffeeScript , NaCl
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