gmirror, geli, gjournal performance

[hideo]

Hi everyone,

I was replacing a disk in a gmirror+geli pair and decided to compare
the performance of gmirror+geli+gjournal before adding the new disk.

When using these three together is the appropriate order to 1) fdisk
and label 2) mirror the disk, 3) geli the partitions, and 4) use the
geli partitions for gjournal label?

With respect to performance, I find the writes to the gjournal disk
about half as fast, which I expected from the benchmarks I've seen.
However, reading a single file is identical between the two:

        dd if=/sofupdates/1.mpg of=/dev/null bs=1m
        994049168 bytes transferred in 34.858793 secs (28516454 bytes/sec)

        dd if=/gjournal/1.mpg of=/dev/null bs=1m
        994049168 bytes transferred in 34.335267 secs (28951258 bytes/sec)

Is this expected? I was under the impression that reads should be
somewhat faster with gjournal.  Is geli decryption the limiting
factor here?

Zach