New to Linux - RAID installation

[ViperLancer]

Re: New to Linux - RAID installation

That is interesting -- thanks for posting it.

The last time I built a Windows system (early 2004), I bought a pair of WD Raptors (72GB) and mated them in a RAID 1 mirror, for data security. That machine has been my wife's for the past 4 years, since I built a Linux box for myself. Earlier this year, I decided 6 years was long enough, and I pulled them and replaced them with a 200GB SATA disk (WD-something, don't remember) and re-installed Win XP for her.

But, the experience of observing 6 years of failure-free operation, plus seeing the MTBF specs on the current generation of conventional hard drives, plus the overwhelming scarcity of reports of hard drive failures, leads me to think RAID 1 is pretty much a waste of a hard drive for desktop computer purposes (assuming some reasonable backup scheme is used).

Also, isn't it the case that conventional hard drives can't saturate the SATA (1, 2 or 6) channel anyway? In other words, even striping them isn't going to get us where a SSD will be in a year or two, right?

Well, since I got my PC back up & running after a hardware failure, thought I'd get back to trying to install Linux! Yay!
My perspective on your questions is this:
About RAID1, it's more of a waste if you do both RAID1 AND run a separate backup. The benefit to RAID1 is you don't risk losing data newer than your last backup if your drive/array fails. The downside, if something is accidentally deleted, it's removed from the RAID1 as well, so you lose protection from that. Personally, I just run a standard backup any time I feel I have new data worth backing up. Since I wrote my own backup, I only keep the single most recent copy of any file, to save space.

As for the SATA question, I believe it would take at least 10-12 HDD's to even hope to saturate a SATA 2 channel. It would depend which SSD's you chose, but I think 4 could do it. Right now, it's still a question of cost/capacity. You get 1/4 the capacity at 4-6x the cost.
If what you need is capacity, go with HDD's.
If what you need is performance & you'd go buy enough HDD's to make up the difference, then it would be worth it to buy SSD's instead, as they are even more reliable, use much less energy, etc. It'd save money in the long run. I read an article somewhere a while back about a person or company who'd switched their HDD's to SSD's, used I think 1/10 the energy, reduced the heat buildup in the system, and improved performance still.

Edit: lol Just realized I'd answered this. Somehow missed reading my own post when I read your question. Sorry.

[ViperLancer]

Re: New to Linux - RAID installation

Okay, so I just found out something very interesting about all this. With my current setup, I can't install Linux.

So to recap, I have 2x RAID0 arrays, each with 2x HDD's in them. I run my OSes on the smaller RAID & data/large programs on the larger RAID.
My BIOS "fakeRAID" I used to create both RAIDs allowed me to create separate arrays on each pair of disks, so I was able to RAID0 a "partition" of only 120GB on my OS drives for Windows, leaving the rest for Linux/whatever.

Kubuntu's installer can't see the non-RAIDed section of the OS disks. I could only access that space from Kubuntu if I used my BIOS to create it as a RAID. Problem is, once I did that, I encountered more errors. For one thing, apparently Kubuntu still obeyed the limitation on # of primary partitions even though it appeared as a separate RAID/drive, so I was only able to create 1. Not exactly a problem as Linux is supposed to be able to work from ANY type of partition. Ignoring that & creating the rest as Logical partitions, Kubuntu failed even being able to create its 1st partition (/boot) under the RAID.

I'm not saying this is Kubuntu's fault at all, just giving the info. I think the BIOS is selectively passing only the RAIDed info to Kubuntu.
This is very interesting, but means a major headache for me. If I want to install Kubuntu, I'll now have to destroy my OS RAID0 for my Windows, thereby also destroying my Windows OSes. Unless anybody knows of some way to get Kubuntu to see the extra space on my OS drives that isn't part of my Windows RAID?

[rihad]

Re: New to Linux - RAID installation

Hey, guys. I was hoping you could me with this. Prior to Kubuntu 11.04 I could successfully boot from a Fake RAID disk, but after the upgrade to 11.04 the kernel could no longer find the device mapper files /dev/dm-* and thus couldn't find the root FS. The initrd disk is there. Same in 11.10. But there's a workaround to that: I first boot a 2.6.35 kernel which was in 10.* I believe, which is able to find and initialize the RAID, and then I reboot into the newer kernel. What is so messed up about it?