raid1 with sata is slow (speed of a single disc)
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
mdadm (Ubuntu) |
Invalid
|
Undecided
|
Unassigned |
Bug Description
Binary package hint: mdadm
I use feisty
Reading from my raid1 is as fast as a single sata disc:
hdparm -t /dev/sda1
/dev/sda1:
Timing buffered disk reads: 172 MB in 3.00 seconds = 57.27 MB/sec
hdparm -t /dev/sdb1
/dev/sdb1:
Timing buffered disk reads: 172 MB in 3.01 seconds = 57.20 MB/sec
hdparm -t /dev/md0
/dev/md0:
Timing buffered disk reads: 172 MB in 3.00 seconds = 57.29 MB/sec
i tried
* different motherboard with a different sata onboard controller but also the same results
* different ubuntu kernels: 2.6.17, 2.60.20 and from gutsy 2.6.22rc
* different images:
linux-
linux-
linux-
can anybody explain me why?
I also witness this since forever; I think this is supposed to be normal for RAID 1 and people are supposed to use RAID 0+1 to get similar speed benefits as for RAID 0.
I'm also curious of the underlying technical reason.