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A question about RAID 5

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October 31, 2011 3:32:51 PM

Hey everyone, I have a quick question about RAID 5, my IT apprenticeship trainer said that if I set-up a RAID 5 system with 3 SATA 3 hard drives it will treble the speeds (i cant remember if he specified anything), as i am planning on building a new computer soon i wanted to look into this to see if its a good idea or not, upon further inspection i quickly found out that apparently RAID 5 decreases the performance for redundancy

can someone please clarify the pro's and con's of RAID 5 (bar money, thats not an issue)

Thanks

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October 31, 2011 3:49:28 PM

is google broke......nope still works. give it a try
October 31, 2011 3:58:19 PM

Wikipedia has enough information for you.

Pro:
cheaper data redundancy than raid 1
increased speed for large writes and all reads

Cons:
data redundancy not as good as raid 1
if the raid is very large it may fail during rebuild since it has to read from all the disks
performance while rebuilding is bad (same with operating with one bad disk)
lots of random small writes have poor performance
most controllers implement raid 5 poorly and performance ends up being bad (so read reviews before making a decision)
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October 31, 2011 3:58:36 PM

Ok let me be more specific, what is everyone's personal experience with RAID 5 like?

i did search google, however i got VERY mixed opinions.
a b G Storage
October 31, 2011 4:35:50 PM

in my experience, the performance of a raid 5 array is dependant on the controller.

if you're building a raid 5 with your motherboards built-in controller then don't expect much and don't be surprised if you see worse performance compared to a single hdd.
i've got a hardware accelerated raid controller running raid 5, it's out-performs any single mechanical hdd i've had.

EDIT: i have three hitachi deskstar 7k3000 2TB drives in raid 5.
one fo those drives by itself will hit ~115MB/s, but three of them in raid 5 configuration on a hardware accelerated controller card i hit 205MB/s
October 31, 2011 6:48:01 PM

I run RAID 5 with 3 WD black 1TBs for storage off the MB controller, havn't had a single problem since I set it up and since it isn't my system drive performance wasn't a concern just storage capacity and data redundency incase of a drive failure.
November 10, 2011 5:26:11 PM

I am running raid 5 off the motherboard controller, after my new hard drives came in, array started up perfectly with no problems started initializing and my dad turned off my computer so it stopped at 76% and I can not get it to initialize in the amd RAIDxpert program

any help guys?
November 10, 2011 8:41:49 PM

Branden said:
in my experience, the performance of a raid 5 array is dependant on the controller.

if you're building a raid 5 with your motherboards built-in controller then don't expect much and don't be surprised if you see worse performance compared to a single hdd.
i've got a hardware accelerated raid controller running raid 5, it's out-performs any single mechanical hdd i've had.

EDIT: i have three hitachi deskstar 7k3000 2TB drives in raid 5.
one fo those drives by itself will hit ~115MB/s, but three of them in raid 5 configuration on a hardware accelerated controller card i hit 205MB/s

QFT (quoted for truth)

Everything Branden said is pretty spot on.

To give an idea, we use all 3Ware controller cards with 128MB of CACHE on the physical card. When using an onboard solution (Intel RAID, SIIG RAID, etc.) you are not using a dedicated controller to handle the way the data is dispersed, you are using the processor to do a low level "software RAID" which in turn is very time consuming to build the entire array, and the more drives/total storage you have, the longer it takes. For instance my boss built an i5 650 (3.2) on an Intel Extreme MOBO that supports RAID 5; building the actual array while trying to use the computer (Win7 Pro 64bit) took nearly 48hours to complete. A similar setup (Xeon 3.0) with a dedicated controller (3Ware on PCI-X not PCI Express) with same size drives (1.5 TB) took roughly 8 hours to complete from start to finish, and this while the server was under partial load.

The difference is that you have a co-processor specifically in place to handle how the data is applied to the drives and does not rely on the CPU to process the requests.

In my experience (I use HighPoint Rocket RAID as I posted HERE) 3Ware, LSI & Adaptec are pretty much slam dunks for business-grade RAID. As for home applications like I listed, HighPoint seems to do the trick just fine, but I do not use the drive to boot off of and only use it as a storage container.

If you are going to use an onboard solution, I would generally stick to a RAID 1/0+1 and stay away from 5 because the parity sets is the part that takes such a long time to create. Remember that a good setup for super-fast booting and data load is running RAID 0 on 2x SSD drives; lightning fast reads.
a b G Storage
November 17, 2011 8:00:07 PM

devin93 said:
Hey everyone, I have a quick question about RAID 5, my IT apprenticeship trainer said that if I set-up a RAID 5 system with 3 SATA 3 hard drives it will treble the speeds (i cant remember if he specified anything), as i am planning on building a new computer soon i wanted to look into this to see if its a good idea or not, upon further inspection i quickly found out that apparently RAID 5 decreases the performance for redundancy

can someone please clarify the pro's and con's of RAID 5 (bar money, thats not an issue)

Thanks


Like Branden said!

If you are using software RAID - like built mother board's RAID most likely it slows when there is a lots of activity...

Here is what happen:

When R/W to to3x drvies RAID volume, the CPU has to R/W thee times (each HDD).
Note this is not a CPU power concern but rather timing
Where hardware raid you can CPU only R/W one time

It's 66% reduction of CPU timing consumption! Most of time when you run HD bench test you wont see the effect, but in real-life application likes VIDEO compression (BD to MKV, AVI, or 25GB BD) then you can see how slow it's

Look for a hardware raid you can use the PCIe, PCIX controller, but i prefer a driver-less hardware raid controllers SPM393, or SPM394.
!