[CentOS] preferred software RAID 10?

Rudi Ahlers Rudi at SoftDux.com
Sat Jul 26 10:02:25 UTC 2008

Ross S. W. Walker wrote:
> Rudi Ahlers wrote:
>> Ross S. W. Walker wrote:
>>> Rudi Ahlers wrote:
>>>> Hi all
>>>> I'm looking at setting up software RAID 10, using CentOS 5.1 x64 - what 
>>>> is the best way todo this?
>>>> I'm reading some sources on the internet, and get a lot of different 
>>>> "suggestions"
>>>> 1 suggestion says to boot up with a Live CD like Knoppix or 
>>>> SystemRescueCD, setup the RAID 10 partitions, and then install Linux 
>>>> from there.
>>>> 2. Another is to setup a small RAID 1 on the first 2 HDD's, install 
>>>> Linux, bootup, and then setup the rest as RAID 10
>>>> The others didn't really make sense to me, so how do I 
>>>> actually do this?
>>>> And then, how do I setup the partitioning? Do I setup /boot on a 
>>>> separate RAID "partition"? If so, what happens if I want to 
>>>> replace the 1st 2 HDD's with bigger ones?
>>> What's the hardware setup?
>> I didn't really specify any, cause I want to keep it purely software. 
>> Generally it would be on a generic PIV motherboard with 4 / 6 
>> SATA, or even mixed SATA & IDE HDD's - all new, so at least 80GB per HDD
> I was primarily interested in the # of HDDs that can be used.
> If you have 6 disks, setup 2 disks as a  RAID1 for the OS and the
> other 4 as a RAID10 for the data.
> If you have 4 disks all together:
> 1) create /boot partition as a 4 disk RAID1 across all 4 disks
> 2) create the remaining space as 2 separate RAID1s of type LVM
> 3) create a VG out of the 2 RAID1 PVs, create root, swap LVs on
> the VG with a stripe of 2.
> LVM striping over multiple RAID1 PVs provides the same performance
> as a native RAID10 array, plus you can add RAID1s later to
> increase the size/performance and dump/restore the data to stripe
> it across the larger set of PVs.
> -Ross
> _____________________________________________________________________
Thanx, this seems like a fairly easy way of doing it.

 From what I gather, the data will fill up from the beginning of the 
stripe, right? So the 1st 2 HDD's will work hardest in the beginning, 
until there's enough data to fill the other 2 HDD's - unless of cause I 
split the LV's across the PV's - i.e. put root on md1 & swap or var on 
md2 for example.

Does swap need to be part of the RAID set? Is there actually a 
performance boost?


Kind Regards
Rudi Ahlers

Check out my technical blog, http://blog.softdux.com for Linux or other technical stuff

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