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I'm using a QNAP-439 Pro II SAN. Full disk encryption is currently enabled. But since you take a 80% performance hit by enabling encryption I'm thinking about disabling encryption on the SAN and offloading it to Windows Server 2008 R2 Machine that I'm currently building anyway.

The SAN is operating on 4x2TB disks in RAID6 mode. Unless I'm mistaken (which is why I'm asking here), a RAID drive failure on the QNAP should be handled transparently to the Windows iSCSI client and should not interfere with Truecrypt right?

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Fwiw RAID6 on 4 disks doesn't really make sense. RAID10 yields the same disk space and also supports 50% redundancy and is much faster. Only advantage is with RAID6 you can have any two disks fail, but with RAID10 you better pray they're not from the same pair. –  Mark Henderson Jul 30 '12 at 8:46
    
After losing an almost brand new 2TB disk not long ago, I became paranoid about redudancy :) –  Oliver Weichhold Jul 30 '12 at 10:39
    
@OliverWeichhold I completely get your choice now, it's funny that I'd by default always go to R10 but given your scenario I fully understand why you went with R5. Personally I'm not a fan of using SATA disks but thanks for making me challenge my own defaults :) –  Chopper3 Jul 30 '12 at 10:57
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You question title is very misleading - the only question you appear to be asking is "will disk failure in an R6 array be transparent to my client", and the answer is yes, in fact you could lose two without any impact whatsoever other than a performance drop until the array was rebuilt.

That said I'm more than a little confused why you've built a four disk R6 - 99% of people would, when they're happy to lose 50% of their available space, choose R10 in your situation due to the performance benefits. Presumably you intend to grow out this array at some point and that's why you've done it? Well done on not choosing R5 though, big disks and R5 is a bad idea.

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You are right on both accounts. Thanks a lot. –  Oliver Weichhold Jul 30 '12 at 10:38
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