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Help explaining RAID and Partitions

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August 27, 2008 1:23:15 AM

So I've never installed RAID and I'd like to on my FREENAS system. I do however have some noob questions.

1. I have 500gb, 750gb and 250gb drive. Can I partition all to the least common denominator (250gb) and then have a RAID 5 setup?

2. Assuming I do this in FREENAS, will the process of setting up RAID erase what's already on these discs (I assume so)

3. Do I need a special disk controller in my PC or will FREENAS do this via the software?

Any other helps, warnings or suggestions?

Michael
August 27, 2008 1:34:44 PM

Heya,

1. RAID automatically will lower all specs to match that of the slowest and smallest drive. You really want to try to have identical drives for RAID for optimal use. In your case, it'll only be 250gigs, wasting those other drives completely. Also, RAID5 isn't so simple just because you have 3 drives. You have to have a controller for it (it'll cost you more than two new drives likely too; RAID5 is not meant for consumer access in general, it's higher so more expensive).

2. When you make an array, it will function as one disc; it'll need to be formatted, so yes, all data is gone.

3. You really should get a controller. Software RAID is just not worth it. If you truly want RAID you need hardware and it needs to be good.

Jumping into RAID for the first time via software RAID and going RAID5 right away will have you at a learning curve. I would suggest you familiarize yourself with a typical two drive RAID0 setup first. Get an idea of it.

By the way, why the push for RAID in the first place?

Very best,
Anonymous
a b G Storage
August 29, 2008 10:19:24 AM

Unfortunately in FreeNAS you can't use partitions for software RAID only whole disks and if you use the 3 you have listed you will lose lots of space. The 3 drives combined as a RAID 5 will only be 500MB. You need to find another drive similar in size to one of the others and go with RAID 1 (or RAID 5 if you can find 3 disks similar in size).

I don't agree with malveaux however with regards to software/hardware RAID. Software RAID is very simple to setup in FreeNAS and the performance will be sufficient for most home needs while enjoying for benefits of redundancy.

There is a video on YouTube showing how to setup RAID 5 on FreeNAS http://www.youtube.com/watch?v=x8-DrhYKTFE .

You might also like the http://www.LearnFreeNAS.com web site.

I hope this helps,

Gary
Related resources
March 25, 2010 11:14:34 PM

Hey Anonymous,

I stumbled on this old thread while trying to figure out a RAID question.
Your answer here states that Software RAID uses only whole disks. What I'm wondering is if Hardware RAID can be set up with partitions in different RAID levels.

To be specific, I'm using an Asus P6T Deluxe V2 with onboard RAID for a video editing system.
(2) 300gb disks
(2) 2tb disks
(1) additional 2tb disk

The (2) 2tb's are for storage (RAID 1), the addtl 2tb is for backup. On the 300gb disks I want to know if I can create a partition for my OS/Apps in RAID 1, and a partition in RAID 0 for scratch disk. And how necessary is backup if I already have the redundancy of RAID 1 storage?
I have not bought the drives yet, so options are open.

Any feedback would be most appreciated!
May 5, 2010 8:48:56 PM

So why not use RAID-Z instead of RAID 5?

According to some research (Wikipedia, no personal experience) FreeNAS has ZFS which "is not limited to similar devices but can consist of ad-hoc, heterogeneous collections of devices, which ZFS seamlessly pools together, subsequently doling out space to diverse filesystems as needed." So your various drives would fit this scheme.

Plus RAID-Z "implements an integrated redundancy scheme similar to RAID 5" and "avoids the RAID 5 "write hole" so it is more efficient.

Or you could use RAID-Z2 "which doubles the parity structure to achieve results similar to RAID 6: the ability to sustain up to two drive failures without losing data."

Look up FreeNAS in Wikipedia and you will see a whole host of options available to you under subtitle "Features". And since it supports "S.M.A.R.T." the software problem should not be a problem.

Let us know how it turns out and good luck.
May 5, 2010 8:57:01 PM

To LocalRipper. Since you have Asus P6T V2 check out the Intel Matrix Storage Controller information and you will find the answer to your question. I have not done it but what I have read is that Matrix Storage can do exactly what suggest.

That RAID controller works off of firmware imbeded in your motherboard on the southbridge and has a load of great features. Do some Wiki research on RAID and check out it's advantages. Also check the specs for your mb and you will see that you have this stuff.
!