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I have a RAID setup questions

My mobo supports hardware RAID, my question is, should I use the board's RAID system or freeNAS/Ubuntu's software RAID system?

I realize performance is better with h/w, but my concern is what happens when a drive fails? I want to go with whatever option allows me to keep the data accessible after failure.

I.E. drive 1 of a RAID 1 pair fails, I want the second drive to still be accessible to me if a) I swap a new drive in and or b) I take the good drive out and put it in another system.

I've never messed with it and I've heard that software RAID setups can render a drive unusable in other systems and I've heard the same said of hardware setups so, which is it??

This setup will be for an NAS type of server.

David Morin
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2 Answers2

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It ultimately depends on the implementation of the RAID that's built into your motherboard but often times this "hardware" RAID is little more than software RAID facilitated through some proprietary drivers that will need to be loaded into the OS.

If this is the case, IMO, it's almost always better to use the stock software RAID that's included with any Linux distro. I've used the mdadm software RAID + tools for over a decade and have never had any issues with it. The performance is solid and there are extensive tutorials and guides available on the internet to walk you through the various task such as setting it up, growing it, shrinking it, add/removing HDDs, etc.

This guide titled: 10 Surprising Facts About RAID also agreed with this position.

2. Software RAID is almost always a better choice than hardware RAID

Software RAID has advanced significantly in the last few years (as of 2012). Hardware RAID still has the three key vulnerabilities it has always had: First, it is expensive. Second, if your RAID card fails, your RAID volume fails; it is a single point of failure. Third, if your RAID card fails, you must find an exact replacement for that card to recover your data. On the other hand, software RAID costs nothing, and if your controller card or motherboard fail, you can just move your disks to another machine and set up the appropriate software to read them. ...

3. Some “RAID cards” aren’t hardware RAID

Over the last few years SATA disk controller cards and motherboards have come out that claim to offer hardware RAID. They are really just disk controllers with BIOS that implements RAID in software. How can you detect these cards and motherboards? Usually price is the giveaway. A $20.00 card is not likely to implement true hardware RAID. Also these cards usually offer windows-only support. Here’s a good writeup.

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slm
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  • The mobo is a Maximus Formula: https://www.asus.com/Motherboards/MAXIMUS_FORMULA/ My plan for this unit is to serve as an in home NAS as well as possibly an in home web server, haven't decided yet. I've heard good things of the mdadm. If I go that route, and decide I want to remove a drive to use it elsewhere, will I run into issues? – David Morin Mar 30 '14 at 16:49
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    @DavidMorin - it almost doesn't matter. Every Mobo I've bought with RAID included and attempted to use I've abandon. None of them were true hardware RAID. These RAIDs are nothing more than a marketing gimmick so that they can squeeze another $10 US out of selling you this feature. Go with a software RAID (mdadm) or a real RAID controller that plugs into your PCI-X bus. – slm Mar 30 '14 at 16:52
  • @DavidMorin - I've used mdadm for 10+ years in home NAS as well as small office NAS' and have never had any issues. If you need to move the RAID members around it's trivial to setup another box with mdadm and migrate them. Using the built-in RAID controller to your MoBo will require you to have the same technology if you need to migrate it. – slm Mar 30 '14 at 16:54
  • Thanks, that's pretty much what my biggest fear was; whether or not 5 years from now if something busts I'd be able to get the stuff back. Sounds like software is the way to go. – David Morin Mar 30 '14 at 17:37
  • @DavidMorin ZFS is also a things to consider, even if it has to be planned. – Ouki Mar 30 '14 at 18:01
  • @Ouki - ZFS is what FreeNAS uses, not sure about a Ubuntu option though. – David Morin Mar 30 '14 at 18:08
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IF you have real hardware RAID support, you pretty much always want to rely on that hardware RAID chip.

However, unless you have a server-class motherboard (and even those are suspect on the low-end), you probably just have a chip that makes software RAID easier, similar to the WinModems of yesteryear. In that case, you're still really doing software RAID. If this is your situation, and you don't have real hardware RAID support after all, you're probably better off relying on the standard/universal software RAID, instead of a proprietary vendor driver.

Joel Coehoorn
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