[CentOS] Multiple RAID support in CentOS?

Ross Walker rswwalker at gmail.com
Sat Jan 30 02:48:45 UTC 2010


On Jan 29, 2010, at 9:16 PM, Brian Mathis <brian.mathis at gmail.com>  
wrote:

> On Fri, Jan 29, 2010 at 9:09 PM, Ian Blackwell <ian at ikel.id.au> wrote:
>> On 30/01/2010 12:09 PM, Victor Padro wrote:
>>> Hello,
>>>
>>> I was wondering if someone could help me,
>> I'll try...
>>> I want to use one array with the 2 500GB HDDs in RAID1 for the OS  
>>> and
>>> for some VMs,
>> That will work OK.
>>> and the other 4 1TB HDDs I want to create an array in
>>> RAID5 or RAID10 for file sharing across my home Network.
>>>
>> You can use these disks in a RAID5 array, but not RAID10.  I fairly  
>> sure
>> you need more than 4.  RAID10 is mirrored, so you only have "2"  
>> disks in
>> the array, which isn't enough for parity/striping stuff.  You need at
>> least "3", which would mean 6 disks for RAID10.
>>
>> Having said that, I'm assuming you want to use the entire hard disk  
>> as a
>> participant in an array.  You could create 2 x 500Gb partions on each
>> disk and then you have 8 x 500Gb partitions to use in a RAID10 array.
>> This approach sacrifices some redundancy though.  If a disk dies
>> entirely, then you will lose two participants in the RAID array,  
>> which
>> may or may not be catastrophic - it depends on what you put where...
>>> I found a guide but it's a little bit outdated and it's for  
>>> Debian...
>>>
>>> Do you have any other pointer I can read/use?
>>>
>> http://wiki.centos.org/HowTos/SoftwareRAIDonCentOS5
>>
>> I've mostly installed RAID arrays at install time, which you'll  
>> need to
>> do as well if you want to put the OS on a RAID1 array.
>>>
>>> TIA.
>>>
>> Ian
>
> RAID10 does not use parity, it's just a mirror of stripes, so 4 disks
> will work perfectly fine with it.
>
> Use RAID10 for speed, and RAID5 if the space is more of an issue.
> With RAID10 you lose 1/2 the total space, and with RAID5 you lose 1
> disk's worth.

Small correction RAID10 is a stripe of mirrors rather then a mirror of  
stripes which does not provide the same resiliency.

-Ross



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