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Re: fc10 and raid-10



Dennis Gilmore wrote:
On Saturday 27 September 2008 09:32:27 pm Bill Davidsen wrote:
The Fedora installer has insisted on requiring four drives for raid-10
install, and then not using raid-10, but rather raid-1+0 which is *NOT* the
same thing. Any hope that this could be fixed in fc10, as it is a real PITA
to fight a way around it and get a proper raid configured.

This is a real performance issue, see linux-raid discussion in archives
about this.


Raid 10 requires at least 4 drives. and then it needs even numbers of disks to grow. so you could do 4,6,8,10,12 etc. an odd disk is should only be used as a hot spare. otherwise it would cause degregation to the array

As I said, raid10 is not the same thing as raid1+0. And since the kernel and installer use the same term for different things, I would say the install should match the kernel code and doc, and not have the user confused. Using the correct term for what the installer really does, raid1+0, would confuse no one.

The man pages for raid and mdadm are helpful in understanding the difference between 1+0 and 10.


md1 : active raid10 sda2[0] sdd2[3] sdc2[2] sdb2[1]
      624623104 blocks 256K chunks 2 near-copies [4/4] [UUUU]

looks like its right to me. this box was installed F-8 and was yum updated to rawhide. my box with raid 10 is using the raid 10 module. i have 4x320gb drives and get great performance out of the array.

hdparm -tT /dev/md1

/dev/md1:
 Timing cached reads:   4868 MB in  1.99 seconds = 2441.54 MB/sec
 Timing buffered disk reads:  256 MB in  3.02 seconds =  84.75 MB/sec


Dennis



--
Bill Davidsen <davidsen tmr com>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot


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