fc10 and raid-10

[Bill Davidsen]

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