Poor ACFS performance on AIX

We're using ACFS on a two-node RAC running AIX 6.1 and 11.2.0.2.  The ACFS filesystem is extremely slow--we run a script that copies files from an ftp server to the acfs filesystem, unzips them, then runs a small perl script to validate the md5 checksum.  It is extremely slow--orders of magnitude slower than if we do the same process with a jfs2 filesystem.   Average i/o write times are in the 300-600ms range, often much higher.  They should be in the 10ms range.  The underlying storage is not the problem--we are using the same storage for a 45T database that can