Comment 7 for bug 1418126

jell, as i'm wroted above.

CentOS use CFQ by default.
Ubuntu server - use deadline by default at lest three years.

So at this moment we have, that all ubuntu deployments use deadline and we don't have any problems with it's
About performance of deadline vs cfq. You may to read this for example:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html-single/Tuning_and_Optimizing_Red_Hat_Enterprise_Linux_for_Oracle_9i_and_10g_Databases/

Load profile databases close enough to the load profile virtualization (many random access with random block size in many threads)