The last day of the conference started with a fabulous presentation by Joshua Drake from Command Prompt. From my former days as a Postgres admin, I recall he was quite the presence on the Postgres mailing list so I was quite excited. He went from bottom to top (could have been top to bottom; hard to tell) on how to make Postgres fast. Among the key concepts were that RAID5 is always to be avoided (use RAID10), put your transaction log on a separate spindle (RAID1 please), and take time to learn EXPLAIN ANALYZE. The details take much longer to learn but if I ever get the chance to run a Postgres database again, these will come in very handy.

Miscellaneous Notes:

• hard drives are the slowest
• raid1 great for pg_xlog
• split transaction log
• raid10 for data, separate raid1 for transaction log
• transcation log on ext2 because it *is* a journal
• don't use raid5
• always always always use a battery backup unit (bbu)
• many controllers will disable cache if no bbu
• max out ram. 98% of data sets fit in 4GB of ram.
• sata is great. get a bbu and get twice as many spindles.
• pg is process-based. more cores, better performance.
• autovacuum is not optional. do it.
• default autovacuum works 99% of the time
• shared_buffers - pre-allocated working cache of tuples
• rule of thumb is 20% of available ram
• check kernel.shmmax
• work_mem - amount a sort, etc can use before it spills to disk
• set work_mem to a larger value if you know a query needs it
• explain analyze shows the sort method and the amount of mem
• maintenance_work_mem - maintenance tasks - analyze, vacuum, create index, reindex
• set maint as high as possible. ceiling, not allocation.
• effective_cache_size - very misunderstood. hint.
• % of cached + shared_buffers = effective_cache_size
• generally 40% to 70%
• log_checkpoints - off by default. correlate between checkpoints and spikes in %IOWait from sar
• checkpoint_timeout - force timeout. 15-20 minutes. default 5.
• checkpoint_completion_target - do not change this
• checkpoint_segments - default 3. set to 10. how many transactions logs before a checkpoint is forced.
• use checkpoint_warning to see if you need more
• each segment is 16MB
• recovery means going through each segment
• wal_sync_method - leave default
• synchronous_commit - wait for wal to be written before client completes
• turn off for faster commits. generally turn off.
• default_statistics_target - arbitrary value to determine stats collected by vacuum
• analyze will take longer, but plan is better
• can be set per-column
• know to increase it with explain analyze. if plan == actual, good.
• sqlite - great unless you need concurrent writes
• seq_page_cost - related to rand_page_cost. cost of fetching from disk. with raid10 set the same.
• cpu_operator_cost - default is 0.0025. 0.5 is better
• cpu_tuple_cost
• connection pooling - use pgbouncer
• skype uses postgresql
• plproxy
• prepared queries hang onto plan for the life of the connection. pooled connections can be problems.
• functions are great for ORM
• execution_cost - higher means function costs more
• no function hints to the planner
• 9 has replication. not ready for production data yet.
• londiste - some kind of skype-made replication
• drbd

I attended Robert Bolton's presentation on amateur (aka ham) radio. I was excited about this one for two reasons. First, radio is radio and I hope that in learning amateur radio I'll better understand the digital radios I use at work. Second, I've had a desire to be a ham ever since I was exposed to it as a wee little Boy Scout. I'll be taking my test in the next couple weeks, if everything goes according to plan (doesn't it always?). The one thing that came out of this presentation and excited me more than anything was that Asterisk has a radio interface (app_rpt) which you can use to create a phone patch system. I realize it's not exceptionally useful, but it does sound like a great project.

Miscellaneous Notes:

• modulation analog: AM, SSB, FM. digital: PSK, FSK, ASK, QAM. spread spectrum: DSSS, FHSS
• ke7zea
• packet radio built into linux kernel
• very slow speeds
• gordon west book on radio theory
• gpredict - satellite tracker
• aprs - gps-based location reporting
• software radio - gnu radio, universal software radio peripheral
• asterisk app_rpt
• ddwrt - can use more power w/ amateur license. call sign as ssid. no encryption.
• echolink - windows based software
• irlp - internet repeater link project

Git has become my favorite version control of late, so I was very excited about this presentation. With that, I attended Tim Harper's presentation on Advanced Git. We got started 30 minutes late, he had some technical issues with his content, and we ended up with only 15 minutes of class time. That was a real disappointment. I did learn about gitk, a repository visualizer. I think I have a somewhat better idea on how to browse around my branches.

Miscellaneous Notes:

• rebase
• clean commits
• bisect
• always review before you commit
• git add -p - yes/no before it adds
• gitk - repository visualizer. gitk --all
• tig - console visualizer
• git log branch1...branch2 - show changes that are same in both branches
• git reflog
• lose your head

Last presentation for the day was from Gabe Gunderson. We were all a little concerned that Gabe would show up. Turned out due to a miscommunication he thought the presentation started half an hour later. Oh, well. Life goes on.

Gabe gave us an introduction to Twisted which is an event driven networking framework. Sounds like a nice way to abstract away the details of a network application. I was particularly interested in this since I'm using Zenoss, which is Python based. So far I can't see quite how this will fit into anything I'm doing.

Miscellaneous Notes:

• event driven network framework for python
• MIT license
• protocols and transports separated
• network and gui share event paradigm
• event driven means debugging is a pain
• events means you have to save context
• "deferreds" are returned by functions that run asynchronously
• common classes: reactor, protocol
• protocol.Protocol - wire protocol (pop3, etc or write your own)
• protocol.ClientFactory - creates instances of class for each connections
• perspective broker

First session of the day was about VMLB IP Load Balancer, presented by Clint Tinsley of Inductys. It's a formerly proprietary application whose development stopped in 2006. They're now looking to relaunch development and build it as Open Source. Overall sounds like an interesting project which could turn into something if the project works out. At this point it's not something I could actually use, unfortunately. I'll have to keep an eye on it.

Miscellaneous Notes:

• project dormant since 2006
• persistent connections to real server
• designed for 2 interfaces
• supports 4 interfaces
• no vlan support
• no snat support
• mgmg ip separate from lb ip
• layer 7 content type awareness
• redundant controllers
• support for ssl processor cards
• http/https/ftp/imap/pop/ldap/smtp
• roundrobin/weighted/least conn/src dst hash/expected delay/never queue
• service checks
• redhat/centos 3.0
• uses ultra monkey - stopped dev in 2005 - or not?
• snort built-in
• built-in help system
• und.cgi - management web app
• ssl proxy for back-end http
• real-time monitoring is missing
• code release next week
• source going in github (ossvmlb)
• release on sourceforge
• custom health checks? does basic alive (ping?). adding new ones might be hard.