Raid 0 - what happens with the data when hdds plugged into another motherboard

There is very little chance that the new controller will recognise a RAID array setup by the old. Sometimes even switching between controllers from the same manufacturer or even the same range can cause the array to not be recognised.

This is one of the reasons I recommend against using the RAID support found on motherboards and cheap I/O cards (the other reason being that that are usually "fake RAID", combining the worst points of hardware and software RAID in one ugly package).

If you use Linux's software RAID then you can just transplant the drives to another machine and more often than not (much more often than not) it will work pretty much automatically. Sometimes a little manual intervention is needed (for instance: if the device node configured conflicts with an existing array in the new machine you need to manually reassemble the array, but this is done with a single mdadm command). I'm guessing other OSs' software RAID solutions will transport between machines as easily, though Linux is the only one I know of for sure as I've performed the operation myself a number of times.

If you don't want to use software RAID then get a good controller card, then you can transplant the controller with the drives or get a new controller of the same type (this doesn't work with cheap RAID controllers because, as with wireless NICs, they sometimes silently switch controller chips between revisions so even though the box has the same part number they aren't necessarily compatible). Good hardware RAID's advantages over software RAID and "fake RAID" are better performance in some cases, complete OS independence, and (if you pay good money) safety features like battery backed cache/buffers.

David Spillett

Posted 2009-12-16T14:01:58.947

Reputation: 22 424

+1 for pointing out the difference between good and bad hardware RAID. Even a fairly-good manufacturer like 3Ware frequently won't allow the drives to be easily moved between controllers. Additionally, whatever card you buy, buy two. That way, when (oops, I mean "if") your card goes out, you still have a card that will work to allow you to salvage your data. Or, have a good backup/recovery plan in place. Finally, never NEVER EVER use "RAID 0". – Adrien – 2010-01-15T18:01:37.127

I see raid 0 as a flexible disposable performance approach. I'm currently using the motherboard controller for a 2-drive raid 0. Everything important is mirrored frequently to an external eSata drive. Personally, I find this 3 drives combination nicer than a 3 drive RAID 5 since it provides the added security of keeping one of the drives away from the power supply, does not depend on RAID at all to retrieve data from my backup, and provides the flexibility of dropping or reconstructing the RAID at any time without much hassle. Fast+Economical+Secure(backuped), at the cost of low resilience. – mtone – 2010-01-15T20:11:14.917

Fair enough, monotone, especially since you realize the risks and have a backup plan; just out of curiosity, though, have you benchmarked your striped array against a single drive, with tests that simulate your real-world workload? In my own experience (YMWV) the performance gain was slight, and not worth the risk of doubling the chance of failure. Of course, I should "never say never". :-) – Adrien – 2010-01-15T21:39:33.583

@Adrien: it depends what you are using the array for. I run databases and small teams of virtual machines for testing from RAID0 arrays and I can tell you that the performance boost (over single drives or a RAID1 array) is definitely worth it in those circumstances. Just make sure that anything you care about is well backed up (i.e. my test DBs and VMs all have backups sat on RAID1 arrays and external media) and for live systems use RAID1+0/RAID10 instead for the performance without the RAID0's distinct lack of resiliance. – David Spillett – 2010-01-15T23:12:36.360

@Adrien. Good question. I have been testing things out a bit, and conclued that having 4 disks in 2 2-drive arrays, one for data and one for OS and programs did not perform as well as I had hoped. I found out that windows 7 on a ICH10 Matrix Raid Storage performs mostly slower on a RAID 0 128k striped using 2 Seagate 1GB 7200.11 SATA. Boot time is longer, and although raw speed is fast, the OS becomes quite sluggish under moderate simultaneous workloads. – mtone – 2010-01-18T18:55:18.750

I do a lot of large file operations (remuxing, etc) and raid1 to raid2 (4 drives) copy had a hard time staying above 80MB/s. Basically, any access to a raid that is being copied onto result in a big sluggish mess that is overall worse than using 3 or 4 independent drives optimally (with different tasks assigned to each). 100MB/s write speed are quite fun under some situations, and I think I will keep one of the 2 raids for a while, along 2 independent drives for the rest (OS, programs, etc). Maybe I'll decide drop the raid thing entirely if there are too many performance drawbacks. – mtone – 2010-01-18T18:57:46.840

One of my many mantras: "use the right tool for the job, and benchmark it occasionally to make sure it's still the right tool..." @David, you're absolutely right, there are situations where the risk can be worth it, especially if you take steps to mitigate the risk. Like I said, I shouldn't have said "Never", but I think we can all agree: "for the vast majority of users in the majority of cases, RAID 0 is probably not the right tool." – Adrien – 2010-01-19T21:29:16.107

Raid 0 - what happens with the data when hdds plugged into another motherboard

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