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ubuntu - RAID 1+0 vs RAID 0+1

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I went with some advice I
was given from someone I know to go with a RAID setup for this server I ordered. The
specs are below. I plan on using this server to host multiple sites in a PHP/MySQL
environment and an SVN repository in Ubuntu Server. I'd like to have a setup where the
primary drive is mirrored so that in the event of failure on a drive the server could
just use the other pair of drives.



I'm reading
on wikipedia
about raid setups and I see RAID 0-5, but don't see a 10 listed on wikipedia.
Perhaps I'm just not sure what I'm looking for, to be honest I've never used anything
RAID.



On-Board Intel ESB2 RAID controller -
0,1,5,10 SATA RAID



Manufacturer:
            SuperMicro
Model / Part Number: 6015P-TR
Processor(s): Dual (2x)
            Intel Xeon 2GHz 5130 Dual Core 64-Bit Processors - 4MB Cache, 1333MHz
            FSB
Memory: 4GB RAM (4x 1GB PC2-5300) - 8 slots on
            motherboard

Hard Drive(s): Four (4) Hitachi 500GB 7200RPM SATA Hard
            Drives
Optical Drive: DVD-ROM
Floppy Drive:
            Included
Network Interface: Dual 10/100/1000 Gigabit Ethernet
RAID:
            On-Board Intel ESB2 RAID controller - 0,1,5,10 SATA RAID
Power Supplies: 2
            (Redundant) - 700W each
Form Factor: Rack Mount -
            1U


I'm not sure the
best route to take with RAID for what I'm looking for as I'm totally new to
it.




/>

update



At
this point, when I select RAID10 from the raid controller and go into Ubuntu server
installation it shows 2 separate 500GB drives instead of a single 1 TB drive. Ubuntu is
not giving me any RAID options duration
installation.



I'm thinking I'm just going to
install everything on one of those 500 GB drives for the server, then have all my site's
data on the other drive.



I need to get moving on
this server, I can't spend weeks working out RAID
issues.



itemprop="text">
class="normal">Answer



The idea
of most RAID levels is to provide better reliability or speed for arrays of disks using
a combination of the below
methods:




  • href="http://en.wikipedia.org/wiki/Data_striping" rel="nofollow
    noreferrer">striping - splits data speed-efficiently across two or more
    disks +speed

  • href="http://en.wikipedia.org/wiki/Disk_mirroring" rel="nofollow
    noreferrer">mirroring - copies the data onto two or more disks
    -capacity
    +reliability

  • href="http://en.wikipedia.org/wiki/Parity_bit" rel="nofollow
    noreferrer">parity - a separate disk(s) to verify the data on the other
    disks is correct
    +reliability



You
have to decide what's most important for you, capacity,
reliability, or
speed.




Raid
1+0



The official name for RAID
10 is RAID 1+0. Raid 1+0 is a good
compromise between speed and reliability as it combines href="http://en.wikipedia.org/wiki/Data_striping" rel="nofollow
noreferrer">striping and href="http://en.wikipedia.org/wiki/Disk_mirroring" rel="nofollow
noreferrer">mirroring. Using Raid 1+0, you will have
1TB of space.



How
a RAID 1+0 hardware controller
works:



+-----------------------------------------------------+
|
            | :
| 500GB 500GB 500GB 500GB | :

| | | | | |
            :
| +-500GB-MIRROR-+ +-500GB-MIRROR-+ | : RAID Controller
| | | |
            :
| +---------1TB-STRIPE--------+ | :
| | |
            :
+-------------------------|---------------------------+

            |
+-------------------------|---------------------------+
| | |
            :
| OPERATING SYSTEM | :

| | | : Software
|
            APPLICATION | :
| |
            :
+-----------------------------------------------------+


It
is important to understand that, with a RAID controller, the operating system knows
nothing about RAID or multiple disks, it will merely see a
plain, single hard drive. All hardware-controlled RAID configuration must be done
through the BIOS.



Redundancy: RAID 1+0 vs RAID
0+1




RAID
0+1 is effectively the same thing as RAID
1+0, just the other way
round:



 RAID 1+0 ¡ RAID
            0+1 
 | 
 [#] [#] [#] [#] | [#] [#] [#] [#] 
 | | | | | |
            | | | 
 +-MIRROR-+ +-MIRROR-+ | +-STRIPE-+ +-STRIPE-+ 
 | | | | |
            
 +----STRIPE----+ | +----MIRROR----+ 
 | ! |



RAID 1+0
is far more commonly used, however, because it has better redundancy (smaller chance of
array failure because of multiple drive failures). The probability of array failure for
each RAID level
is:




  • RAID
    1+0    : 1 drive fails: 0 (0%), 2 drives
    fail: ⅓ (33%)    , 3 drives fail: 1
    (100%)

  • RAID
    0+1    : 1 drive fails: 0 (0%), 2 drives
    fail: ⅔ (66%)    , 3 drives fail: 1
    (100%)



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