jm + ops + sdd   1

Migrating from MongoDB to Cassandra
Interesting side-effect of using LUKS for full-disk encryption: 'For every disk read, we were pulling in 3MB of data (RA is sectors, SSZ is sector size, 6144*512=3145728 bytes) into cache. Oops. Not only were we doing tons of extra work, but we were trashing our page cache too. The default for the device-mapper used by LUKS under Ubuntu 12.04LTS is incredibly sub-optimal for database usage, especially our usage of Cassandra (more small random reads vs. large rows). We turned this down to 128 sectors — 64KB.'
cassandra  luks  raid  linux  tuning  ops  blockdev  disks  sdd 
february 2014 by jm

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