RAID10 not working in install

Bill Davidsen davidsen at
Mon Feb 25 20:54:43 UTC 2008

Alan Cox wrote:
>> The raw read speed on a RAID1 array is the speed of a single drive. The 
> No. A smart raid1 driver will use both source disks. The raw write speed
> is that of the slowest drive (plus overhead).
Does this mean that the Linux software RAID is not smart, or there's a 
way to make it actually do this?  Current FC[678] doesn't seem to be 
> RAID 10 gives you better write throughput which on a modern PC normally
> means that with PCI Express your bridge/memory bandwidth becomes the
> limit.
This is what I measure running an E6600 CPU and 3xSeagate 320 with 
Recent FC7 kernel. All reads and writes to the raw array using dd, 1MB 
buffer, 1GB i/o to/from /dev/{zero,null} for raw speed. Units are MB/s, 
64k chunks, speed as reported by dd.

RAID lvl        read        write
0               110         143
1                52.1        49.5
10               79.6        76.3
10f2            145          64.5
raw one disk     53.5        54.7

> Alan

Bill Davidsen <davidsen at>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 

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