dmraid: Reads only from one half of a raid01 fakeraid setup

[Bryan Donlan]

I have a RAID01 fakeraid array set up using my Intel motherboard's RAID BIOS. Array initialization has already been completed. While dmraid detects this array and configures it properly, reads are issued only to one half of the RAID-1 pairs in the RAID01 array. dmraid should configure reads to be routed to both drives in each pair, to improve read performance.

# dmraid -s -s
*** Group superset isw_fbbcdgeig
--> Active Superset
name : isw_fbbcdgeig_daruma
size : 3907041792
stride : 128
type : raid01
status : ok
subsets: 2
devs : 4
spares : 0
--> Active Subset
name : isw_fbbcdgeig_daruma-0
size : 1953520896
stride : 128
type : mirror
status : ok
subsets: 0
devs : 2
spares : 0
--> Active Subset
name : isw_fbbcdgeig_daruma-1
size : 1953520896
stride : 128
type : mirror
status : ok
subsets: 0
devs : 2
spares : 0

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: dmraid 1.0.0.rc16-4.1ubuntu3
ProcVersionSignature: Ubuntu 2.6.38-10.44-generic 2.6.38.7
Uname: Linux 2.6.38-10-generic x86_64
Architecture: amd64
Date: Sun Jun 26 22:53:14 2011
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
ProcEnviron:
 LANGUAGE=en_US:en
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: dmraid
UpgradeStatus: No upgrade log present (probably fresh install)

[Bryan Donlan (bdonlan)]

Evidence of only reading from one half, from iostat -x:

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 1071.40 106.80 283.80 13.40 5421.60 480.00 39.71 1.40 4.72 4.05 19.10 2.12 63.00
sde 0.00 106.80 0.00 13.20 0.00 479.20 72.61 0.16 11.82 0.00 11.82 2.27 3.00
sdf 1111.00 107.00 287.80 13.40 5594.40 480.80 40.34 0.98 3.25 2.82 12.39 1.77 53.40
sdg 0.00 106.60 0.00 13.80 0.00 480.80 69.68 0.12 8.41 0.00 8.41 3.91 5.40