fc10 and raid-10
Bill Davidsen
davidsen at tmr.com
Mon Sep 29 19:26:00 UTC 2008
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
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