June 2011
1 post
SSD lifespan →
May 2011
1 post
“On some ssd devices, “smartctl -A” will show you the...”
April 2011
2 posts
Summary of the Amazon EC2 and Amazon RDS Service... →
EBS Durability
See: http://aws.amazon.com/ebs/ It’s pretty clearly disclosed that EBS volumes aren’t terribly durable. So in fairness, it is what it is and is disclosed as it is. An annual failure rate for a volume of 0.1% – 0.5% is mentioned. That means you should be prepared to lose a volume: it could happen. Backups / snapshots would suffice if you don’t mind losing your data since the last...
Interesting MySQL Deck →
Java GC Basics
Basic notes on Java garbage collection that every system engineer dealing with Java in production should know.
Always run with gc logging enabled.
Watch for promotion failures in the gc log. If you are have any, the heap is fragmented, restart the process.
GC time seems to be proportional to size of the heap. GC’s will be slow with a 10GB heap size.
The CMS collector has better...
Graceful Degradation
Long long ago, at DoubleClick, we added to the DART ad server a feature called “dot mode”.
Basically it worked like this: on an ad request, if we have more than a certain # of concurrent threads active, return a 1x1 clear gif (and do no computation or logging). That is, if we are backlogging, don’t serve an ad.
One nuance with the above is that any load balancing system in...
300,000 requests / second →
Pretty neat.