linux-4dtq:~ # uname -r
2.6.27.12-except_export+readahead
-scheduler = deadline
- RA = 4M


linux-4dtq:~ # free
             total       used       free     shared    buffers     cached
Mem:        508168     111288     396880          0       4476      62648
-/+ buffers/cache:      44164     464004
Swap:            0          0          0


linux-4dtq:~ # echo deadline > /sys/block/sdb/queue/scheduler
linux-4dtq:~ # echo deadline > /sys/block/sda/queue/scheduler
linux-4dtq:~ # cat /sys/block/sdb/queue/scheduler
noop anticipatory [deadline] cfq
linux-4dtq:~ # cat /sys/block/sda/queue/scheduler
noop anticipatory [deadline] cfq

linux-4dtq:~ # echo 1 > /sys/block/sda/queue/context_readahead
linux-4dtq:~ # echo 1 > /sys/block/sdb/queue/context_readahead
linux-4dtq:~ # cat /sys/block/sdb/queue/context_readahead
1
linux-4dtq:~ # cat /sys/block/sda/queue/context_readahead
1

linux-4dtq:~ # blockdev --setra 4096 /dev/sda
linux-4dtq:~ # blockdev --setra 4096 /dev/sdb
linux-4dtq:~ # blockdev --getra /dev/sdb
4096
linux-4dtq:~ # blockdev --getra /dev/sda
4096

linux-4dtq:~ # mdadm --assemble /dev/md0 /dev/sd[ab]
mdadm: /dev/md/0 has been started with 2 drives.
linux-4dtq:~ # vgchange -a y
  3 logical volume(s) in volume group "raid" now active
linux-4dtq:~ # lvs
  LV   VG   Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  1st  raid -wi-a-  46.00G
  2nd  raid -wi-a- 374.00G
  3rd  raid -wi-a-  46.00G

scst: Using security group "Default" for initiator "iqn.1996-04.de.suse:01:aadab8bc4be5"
iscsi-scst:		Negotiated parameters: InitialR2T No, ImmediateData Yes, MaxConnections 1, MaxRecvDataSegmentLength 262144, MaxXmitDataSegmentLength 131072,
iscsi-scst:     MaxBurstLength 1048576, FirstBurstLength 262144, DefaultTime2Wait 2, DefaultTime2Retain 0,
iscsi-scst:     MaxOutstandingR2T 1, DataPDUInOrder Yes, DataSequenceInOrder Yes, ErrorRecoveryLevel 0,
iscsi-scst:     HeaderDigest None, DataDigest None, OFMarker No, IFMarker No, OFMarkInt 2048, IFMarkInt 2048

1) dd if=/dev/sdb of=/dev/null bs=64K count=80000
a) 54,1 MB/s
b) 55,6 MB/s
c) 54,3 MB/s

2) dd if=/dev/sdc of=/dev/null bs=64K count=80000
a) 71,3 MB/s
b) 73,8 MB/s
c) 72,7 MB/s

3)Run at the same time:	
while true; do dd if=/dev/sdc  of=/dev/null bs=64K; done	
dd if=/dev/sdb of=/dev/null bs=64K count=80000
a) 4,3 MB/s
b) 5.0 MB/s 
c) 5.2 MB/s