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Constant Resyncs With Windows 7 Software RAID

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Despite my switch to a MacBook Pro almost six years ago I still have a Windows box I occasionally use, mostly when I forget to bring my MacBook’s PSU (which happens surprisingly often, despite having two of them for exactly that reason).

Since disk space on rotational drives is cheap these days I switched to a RAID 1 configuration when I last upgraded the hardware in said computer. I went with two Western Digital WD20EARX 2 TB drives and first tried my mainboard’s fake RAID (AMD RAIDXpert on an AMD SB710 chipset). Long story short, I was unsatisfied with the performance and afraid of data loss in case my mainboard dies and I couldn’t get one with the same chipset.

I’ve seen software RAID on Linux and it was working much better for me than my mainboard’s attempt at it, so I figured I’d try the software RAID implemented in Windows 7 (Professional, Enterprise and Ultimate only). Simple to setup and with acceptable sync speeds I thought I had found what I was looking for – but then it seemed every time I rebooted, the disk array would be inconsistent and resync from scratch. Needless to say, performance was plummeting. The machine would hang for seconds waiting for I/O and every reboot would make it all start over. Even worse, the resync couldn’t be aborted and the disk array couldn’t be disbanded either (who at Microsoft thought that was a good idea?).

Turns out the culprit was a known one. KB 2913050 says “Mirrored RAID volumes report Resynching status after you restart Windows 7 […]”, and it would happen after each hotfix package installation, so for infrequently used computers basically every (re-)boot. I especially liked the “resolution”:

Microsoft is aware of this issue and intends to address it in a future release of Windows.

Translation:

It’s broken, but we’re not going to bother fixing it in Windows 7. Give us some money, if you want RAID support.

Or you could set the following magic registry keys, but we’re not going to tell you what they do, how they affect the Volume Shadow Copy Service or why we’re not setting them with a hotfix for everybody.

Please, somebody remind me why I thought Microsoft had a good reputation for their support of business-grade software…

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