How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs

[Stan Hoeppner]

Neil Brown put forth on 8/4/2010 5:24 PM:

> Both page-cache and read-ahead work at the filesystem level

Are you referring to /sys/block/sdx/queue/read_ahead_kb?  I'm pretty sure this
works below the FS level and below the partition level.  This read_ahead works
at the block device level.  At least for individual or JBOD.

Are you saying this setting gets ignored by the kernel if/when mdadm, LVM,
and/or crypto are used?

-- 
Stan