"Misbehaving" hard disk or weird RAIDframe problem

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

        Hello,

I've created a RAID 1 volume with RAIDframe ...

Components:
           /dev/wd2e: optimal
           /dev/wd3e: optimal
No spares.
Component label for /dev/wd2e:
   Row: 0, Column: 0, Num Rows: 1, Num Columns: 2
   Version: 2, Serial Number: 2009011000, Mod Counter: 51
   Clean: No, Status: 0
   sectPerSU: 128, SUsPerPU: 1, SUsPerRU: 1
   Queue size: 100, blocksize: 512, numBlocks: 312581632
   RAID Level: 1
   Autoconfig: Yes
   Root partition: No
   Last configured as: raid1
Component label for /dev/wd3e:
   Row: 0, Column: 1, Num Rows: 1, Num Columns: 2
   Version: 2, Serial Number: 2009011000, Mod Counter: 51
   Clean: No, Status: 0
   sectPerSU: 128, SUsPerPU: 1, SUsPerRU: 1
   Queue size: 100, blocksize: 512, numBlocks: 312581632
   RAID Level: 1
   Autoconfig: Yes
   Root partition: No
   Last configured as: raid1
Parity status: clean
Reconstruction is 100% complete.
Parity Re-write is 100% complete.
Copyback is 100% complete.

... on these two disks yesterday:

ahcisata0 at pci0 dev 31 function 2: Intel 82801GB/GR AHCI SATA Controller
[...]
ahcisata0 port 2: device present, speed: 1.5Gb/s
ahcisata0 port 3: device present, speed: 3.0Gb/s
[...]
wd2 at atabus4 drive 0: <FB160C4081>
wd2: drive supports 16-sector PIO transfers, LBA48 addressing
wd2: 149 GB, 310101 cyl, 16 head, 63 sec, 512 bytes/sect x 312581808 sectors
wd2: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100)
wd2(ahcisata0:2:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100) 
(using DMA)
wd3 at atabus5 drive 0: <ST3160815AS>
wd3: drive supports 16-sector PIO transfers, LBA48 addressing
wd3: 149 GB, 310101 cyl, 16 head, 63 sec, 512 bytes/sect x 312581808 sectors
wd3: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd3(ahcisata0:3:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) 
(using DMA)

They should be the same kind of disk (one OEM, one retail). The problem
is that the performance of the RAID 1 is abysmally slow.

I tried to run "systat vm" while trying to use the RAID 1 and the result
is interesting:

Disks: seeks xfers bytes %busy                                        512 fmin
[...]
   wd2         154 1202K  98.7                                            pdfre
   wd3         154 1205K   1.8                                            pdscn
[...]
 raid1         154 1202K  99.1

Any ideas how to figure out why the array is waiting for "wd2" all the time?
If I run "dd" from the raw disk device I get reasonable performance from
both disks:

tron@colwyn:~tron#dd if=/dev/rwd2d bs=1024k count=256 of=/dev/null
256+0 records in
256+0 records out
268435456 bytes transferred in 3.457 secs (77649828 bytes/sec)
tron@colwyn:~tron#dd if=/dev/rwd3d bs=1024k count=256 of=/dev/null
256+0 records in
256+0 records out
268435456 bytes transferred in 3.475 secs (77247613 bytes/sec)

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/