A memo to myself regarding RAID setup.

[theweaselking]

Three and a half years ago, I needed to convert a working Linux server from a single valid HDD to running a software RAID-1 mirror. It took several hours of research, several hours of work, four reboots, a near heart attack, and inspired heavy drinking.

Today, I needed to convert a Windows server from a single HDD to running a software-controlled RAID-1. Same hardware - literally, the EXACT same hardware, because this is coincidentally the exact same server machine, having been sold twice, wiped, and then returned to me by a different client for setup. No, really.

The procedure was:
1) Start Disk Management
2) Delete all partitions on the to-become-the-mirror disk, leaving it "unallocated".
3) Right-click on partition #1 of the to-be-mirrored disk, click "create mirror", click the second disk, click OK.
4) Right-click on partition #2 of the to-be-mirrored disk, click "create mirror", click the second disk, click OK.
5) Do something else while the little progress meter runs as the drives sync.

Poof!

There is an important message in this, somewhere.

Comments

[argonel.livejournal.com]

Have you looked at the state of software raid in Linux recently? I understand it is also quite easy to work with now. 3.5 years allows for lots of improvements. Of course I haven't actually tried it myself so it may still suck and inspire heavy drinking.

[theweaselking.livejournal.com]

The Windows software in question is from the same era!

(Ubuntu 10.04 does not APPEAR to handle being migrated from a single disk to an md mirror of two of that same disk any more gracefully than 6.06 did.)

Not just RAID but everything on Linux

[emmeff.myopenid.com (from livejournal.com)]

This is an age-old problem on Linux... those who possess the knowledge to make these awesome features either cannot (most engineer designed UIs are terrible) or don't care about making them user friendly. Say what you will about a UI-driven server management experience, but Windows Server has it locked up. I am not saying a UI-only management experience, but more like something that manages config files for the more complex apps.

Re: Not just RAID but everything on Linux

[xenogram.livejournal.com]

http://thedailywtf.com/Articles/Classic-WTF-The-Complicators-Gloves.aspx

Re: Not just RAID but everything on Linux

[emmeff.myopenid.com (from livejournal.com)]

I'm honestly not sure how that article relates to having a UI for system management, but good story just the same. I'm not trying to be a complicator. Having grown accustomed to GUI-based environments and grown tired of memorizing obscure CLI arguments, I don't think it's too much to ask for something a little more modern for managing complex tasks.

I've been running software RAID on Linux for many years now on my server. If anything goes wrong, I'm forced to drag out the Software RAID HOWTO and figure out what I need to do. A properly crafted GUI wrapping the mdadm tool would alleviate the need for that.

Re: Not just RAID but everything on Linux

[theweaselking.livejournal.com]

If you do things correctly from the start, software RAID and LVM is easier in Linux than Windows. And Linux handles onboard hillbilly "hardware RAID" better than Windows Server does. But in Windows? Correcting a mistake[1] (installing on a single drive rather than on a RAID virtual drive) was easy.


[1]: Notably, last time this was my mistake. This time it was not my mistake.

[anivair.livejournal.com]

I think the lesson is that there are plenty of things that linux can learn from windows. that's why I'm still a big supporter of Ubuntu. Because Mark Shuttleworth gets that message, even though many linux users hate it (myself included sometimes).

[scifantasy.livejournal.com]

You mean, besides shoot the hostage?

[kowh.livejournal.com]

Huh, I did the same thing a couple years ago on CentOS 4 and it was about as easy as your Windows mirroring, just done via the command line. It was already a RAID supporting kernel and VGed though.

On the other hand, I'm annoyed at Windows software raid because they restrict it to the more expensive versions, so I can't use it on my gaming PC.

[theweaselking.livejournal.com]

Your gaming PC's BIOS almost certainly supports hardware RAID.

Also: Really, converting from hda +hdc to md was one command per partition, no reboot required? That's a NEAT-ass trick - how's it do it? I've got a CentOS 5.4 machine I was planning to re-install rather than bother with this since the machine has nothing important on it, but I'd love to try it live.

[kowh.livejournal.com]

Ah, fakeraid. Often worse than no raid at all. If that mobo bites it, it's usually a PITA to recover the data. A Linux software raid disk can just be plonked into another system and booted, albeit sometimes with a little rescue disk greasing to fix incompatible hardware differences.

I'm not sure if I used this exact doc, but it looks familiar: http://tldp.org/HOWTO/Software-RAID-HOWTO-7.html#ss7.6

[theweaselking.livejournal.com]

So, not *quite* as simple - you've effectively booted to a liveCD and treated the two hard disks as unrelated data-only drives - but still a clever way of doing it.

[kafziel.livejournal.com]

The lesson here, I think, is Haters Gonna Hate.

[krinndnz.livejournal.com]

I tried to do a similar thing via hardware RAID, recently (replace the disk in a mirror that had gone bad) and wound up with a nonbootable Windows (7) machine. Sadness.

[theweaselking.livejournal.com]

Hardware RAID-1 always makes me a little nervous that the machine is going to think the replacement drive is the good drive. RAID-5 has other problems, but at least I know that two out of three drives agree that the third one is the one that's got the errors!

[harper-knight.livejournal.com]

The whole RAID shenanigans is vaguely amusing; the coincidence of the machine is hilarious.

[theweaselking.livejournal.com]

It's even still got my original "service tag" shenanigans sticker on the side, leaving aside the identical serial number!

[skiriki.livejournal.com]

I managed to set up a software RAID (mirroring) in my Fedora install pretty easily this summer; it was point-and-click, pretty much.

[theweaselking.livejournal.com]

Once again: Rebootless? Desktop or Server? And, how? Because my best suggestions for Linux *so far* tell me that it's way easier to install on a RAID/LVM drive, but harder to convert after the fact.

[skiriki.livejournal.com]

Server. And sadly, I cannot say "rebootless", because I was installing the whole thing from ground up, and setting up the RAID in installation phase. So my scenario doesn't exactly apply here, it is kind of like bananas and cod, innit? However -- *knocks on wood in a superstitious manner* -- should it happen to be so that I must redo the whole thing, I will write down my experience for comparison. But of course I hope it won't happen.

However, I will say that it was remarkably painless when compared to setting up a hardware RAID in 2003... that required a special kernel hack and even then it did not work properly despite the assurances of the hardware seller that yes, yes, it is totally compatible with Red Hat 8.0. :/

[theweaselking.livejournal.com]

Installing onto RAID/LVM/both is really easy in Linux. The problem is *moving to* RAID/LVM post-install, without wiping.

[theweaselking.livejournal.com]

Also: Hardware RAID *should* be completely seamless to the OS. Ideally, the OS never knows that the "RAID" device is anything other than an IDE, SATA, or particularly odd SCSI device. That's the WHOLE POINT of hardware RAID.

[skiriki.livejournal.com]

Certainly, except the troubles I had in 2003 were slightly more ... "interesting" if you know what I mean. I can tell more later, right now I am writing this at work via my phone...