Expected performance for various RAID configurations

Hi guys,

I'm thinking of getting one of these:


Small partition for Windows 2012 and one big Storage Drive:

I'd prefer redundancy but not crucial as I can replicate data if needs be.....

Could anyone hazard a guess at estimated read/write speeds for Raid 0, Raid 1, Raid 5 and Raid 10.

Assume all drive except the OS will be part of the Raid (11 drives and 1*4TB for OS)

Many thanks.....
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Paul MacDonaldDirector, Information SystemsCommented:
What you probably mean is you'd prefer fault-tolerance (not redundancy).  The next question is "how much are you willing to spend on drives?".  RAID 1 and RAID 10 offer good fault-tolerance, but you lose half your storage to redundancy (to achieve fault-tolerance).  RAID 0 offers no fault-tolerance (or redundancy) at all.  RAID 5 is a compromise in that it's not as fast as RAID 1 or RAID 10, but you get to use more of your disks while still achieving good fault-tolerance.

RAID performance will also vary based on factors outside the array itself.   That said:
Understanding RAID Performance at Various Levels

Online RAID calculator

RAID levels comparison chart

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Those charts above, respectively are only good if you use the same controller and do not experience any bus saturation.  Real world, this won't happen unless you limit yourself to 3 mechanical disk drives.   In other words, they're nearly worthless.

Now since you're using Win2K12, I have a suggestion.  Save the money on a RAID controller and go host-based software RAID1 and use the SATA ports on the motherboard.  With native windows software RAID1 & RAID10 you get read load balancing.    You will not have any bus saturation but are limited to 4 HDD total.  So do a pair of RAID1s.  

Read load balancing means read i/o is done in parallel on both disks in the raid set.   In perfect world reads will be 2X faster in RAID1 then whatever it is on a single disk.  Writes will be the same as a single disk, so no worse off.    As for RAID5, forget it.  Write performance is awful.   RAID10 won't be bootable.  So there you have it.  Simple, a pair of RAID1s and put O/S on one pair.  then on the other disk, set NTFS to a larger chunk size, specifically 64KB, because that is the native I/O size of sql server.     (That is another problem with controller-based RAID. the native I/O size is going to be fixed and won't necessarily be as efficient as software RAID)
ChoakemAuthor Commented:
Fast response and links provided gave me all the information was looking for!


Much appreciated
ChoakemAuthor Commented:

Sorry for not mentioning you but I closed it off before I saw your response :P

That machien I quoted is access to a remote machine in a data centre - I dont get much choice to configuration other than whats offered and thats 12 HD

But i have the info i relly wanted.

thx for the response
Re-read the question, and saw the 11 disk thing.  So still do the O/S on the native SATA you ports software RAID1.  Also put swap there.  Then go with RAID6 because RAID5 with 9 disks exposes you to data loss in event of a drive failure.  Any bad block on remaining drives will mean you lose data, even though only one disk actually failed.    RAID6 has parity spread out on two drives.    

Understand though that you will get bus saturation so performance will be limited to the choice of controller and PCI bus speed.  You'll need to be specific on what controller you choose if you want to know speed.   Random I/O won't be affected by the saturation due to latency.  Throughput will be limited.  Read traffic on RAID5 or RAID6 will pretty much be a wash.   Write traffic will be awful, but you can use the RAID1 with SATA and put log files and write intensive things.
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