Linux compatible raid 5 controller

Khannie

Anyone know of any reasonably priced raid 5 sata controllers for linux?

Software based one is fine. No shortage of processing power atm and performance isn't a major requirement. I have a preference for a 5 or 6 port card but would go with 4 in a squeeze.

Edit: Or is there a way to do raid 5 in software with linux? I currently have 3 drives in an LVM setup but I'm concerned about the potential for catastrophic data loss if one of the drives goes tits up.

Khannie

So, I found quite a bit on software raid for 2.4 kernels, and a nice article on the gentoo wiki which doesn't mention kernel version, but it looks like software raid is supported in linux, which is really all I'm after, so I'll just buy a crappy controller card.

Anyone actually used software raid 5 in linux before? Any experience with replacing a failed drive successfully?

leeroybrown

Have a look at Rick Moen's rather excellent Linuxmafia Knowledgebase page on the matter. That will give you a reasonably up-to-date summary of the available SATA raid hardware.

Personally I'd keep away from any of the software based 'fake-RAID' cards. I have a Adaptec 2610SA (Dell rebranded) full hardware RAID controller that I picked up on eBay. I run a five drive RAID-5 configuration with it. I wouldn't call the performance brilliant but it provides the extra fault tolerance I'd like to have. My choice was dictated by a combination of price and eBay availability. I run an LVM setup over the hardware raid container to allow online capacity expansion.

Linux software RAID-5 does work and is reasonably fast _but_ I wouldn't like to sit important data on it on a home PC. By this I mean that I'd be happy to use it if I knew the machine it was on was in a stable environment where I could test updates, etc but I have seen a few bugs go into kernel updates over the years that would scrub a RAID-5 if you're unlucky. That said it's probably still more reliable than an unprotected LVM over three drives.

Khannie

If you don't mind me asking, how much did your hardware raid 5 card cost on ebay?

leeroybrown

Approx €140 including shipping from the US about 18 months ago.

I bought it at the time because my space requirements were pushing past the capacity of the software RAID-1 setup I had at the time and drive prices made it make sense. I bought two extra 250Gb drives at the time and recently added the fifth as things were getting tight again.

TBH I'd hazard a guess that the stability of software RAID-5 has improved a bit since I originally experimented with it a few years ago so the economics might be on the side of managing the risks with it. I haven't investigated it's stability extensively for quite a while. Also, while I like the security of a dedicated hardware RAID controller I'd be a tad fscked if I needed to dig one up at short notice in the event of a hardware failure.

bminish

Khannie wrote:

Anyone actually used software raid 5 in linux before? Any experience with replacing a failed drive successfully?

Yeah, I am using software raid5 in my own desktop machine, 3x SATA drives and a recent kernel 2.6.18 ish i think. I have been using this for over a year with zero issues

It works fine, I haven't had to replace a failed drive yet but I did recover just fine from a terminally stupid dd copy to the wrong device (I.e overwriting one of the raid 5 disks.

been using linux with software mirroring raid for a long time now too and that works just fine. These days I would not do hardware RAID unless it's REAL hardware raid on decent hardware. When evaluating hardware solutions try and find something that has proper open source support and allows you to monitor it's health. No good finding out about the first drive failure only when the third one fails and there are no more hot spares..

.brendan

Khannie

Nice one. Thanks. Almost definitely gonna go with the kernel software raid.