Multiple RAID support in CentOS?
 

Hello,

I was wondering if someone could help me, I'm putting together a
Server for personal use, I want to virtualize a few servers(mail, web,
ssh) and use it as a NAS, but I have a question if I can use Multiple
RAID Arrays using the following HW:

Intel Xeon Quad Core X3430
ASUS P7F-M LGA 1156
- LSI MegaRAID(integrated)
- HighPoint RocketRAID 2640x1
2 Hitachi 500GB HDDs
4 Hitachi 1TB HDDs

I want to use one array with the 2 500GB HDDs in RAID1 for the OS and
for some VMs, and the other 4 1TB HDDs I want to create an array in
RAID5 or RAID10 for file sharing across my home Network.
I found a guide but it's a little bit outdated and it's for Debian...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?


TIA.

--
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"Everything that irritates us about others can lead us to an
understanding of ourselves"
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Multiple RAID support in CentOS?
 

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 I found a guide but it's a little bit outdated and it's for Debian...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
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Multiple RAID support in CentOS?
 

On Fri, Jan 29, 2010 at 9:09 PM, Ian Blackwell <ian@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.
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Multiple RAID support in CentOS?
 

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

> On Fri, Jan 29, 2010 at 9:09 PM, Ian Blackwell <ian@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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Multiple RAID support in CentOS?
 

On Fri, Jan 29, 2010 at 8:09 PM, Ian Blackwell <ian@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
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> CentOS mailing list
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> http://lists.centos.org/mailman/listinfo/centos
>

Thank you Ian, but I disagree in your concept of RAID10:

[quote]
RAID 10
RAID 1+0 (or 10) is a mirrored data set (RAID 1) which is then striped
(RAID 0), hence the "1+0" name. A RAID 1+0 array requires a minimum of
four drives: two mirrored drives to hold half of the striped data,
plus another two mirrored for the other half of the data. In Linux MD
RAID 10 is a non-nested RAID type like RAID 1, that only requires a
minimum of two drives, and may give read performance on the level of
RAID 0.
[quote]

I'll read that howto, is for fakeRAID though...

TIA

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Linux User #452368
http://twitter.com/vpadro

"Everything that irritates us about others can lead us to an
understanding of ourselves"
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Multiple RAID support in CentOS?
 

On 30/01/2010 1:42 PM, Victor Padro wrote:
> I'll read that howto, is for fakeRAID though...
> TIA
>
>
Yes, I got RAID10 wrong - knew I would (haven't used it before). If
you're using hardware RAID, then the Op/Sys will just see two disks and
you don't really need a HowTo. How you partition/use them is up to you
when you install. I know there is continuous debate about hardware vs.
software RAID, but I've only ever had problems with hardware, and never
any problems with software. Your mileage may vary :)

Ian
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Multiple RAID support in CentOS?
 

> [quote]
> RAID 10
> RAID 1+0 (or 10) is a mirrored data set (RAID 1) which is then striped
> (RAID 0), hence the "1+0" name. A RAID 1+0 array requires a minimum of
> four drives: two mirrored drives to hold half of the striped data,
> plus another two mirrored for the other half of the data. In Linux MD
> RAID 10 is a non-nested RAID type like RAID 1, that only requires a
> minimum of two drives, and may give read performance on the level of
> RAID 0.
> [quote]

Please do note that md raid10 IS different from doing nested md raid1+0.


The md raid10 module does other fancy stuff.
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