Monday, 31 October 2011

Shopping comparison

Did a shopping comparison of ReclaiMe Free RAID Recovery vs Runtime's RAID Reconstructor the other day. Looks kind of grim for RAID Reconstructor.

Thursday, 27 October 2011

Can I has a write hole?..

in a RAID 6?

Actually, yes.

RAID 6 WRITE HOLE

All it takes is large number of disks in array, intensive I/O, a power failure, and some bad luck.

Monday, 17 October 2011

RAID 5 vs RAID 6

I'm getting tired of people advocating RAID 5 vs. RAID 6. They go on like oh, in a RAID 5 a bit error URE will get you one day! We spent 10,000s dollars sending our RAID5s to OnTrack. Yes, that's tens of thousands of Uncle Sam Dollars.

Single bit error in a RAID 5 is much cheaper to recover from than a RAID 6 controller failure or an operator accidentally deleting the array. Ever asked for a quote on RAID 6 recovery?

Tuesday, 11 October 2011

Non-standard configurations

Some do actually like non-standard hardware and software setups.

If we build a 16 TB RAID 5 (9x 2TB), can we then install Windows on it?

Probably yes, with some U/EFI trickery, but then troubleshooting this contraption if hardware ever dies would be a nightmare with 9 drives.

Now another try

We have a leftover of drives, like all sorts of 160GB to 2TB Parallel ATA, all sorts of Serial ATA, five RAID/HBA controllers, and a motherboard. We thought of putting it all together and deploying ZFS over it. Do you think it is a good idea?

Actually, no.

The complexity of the failure modes for the proposed design is just mind-boggling. First of all, when ZFS crashes, there is no reliable data recovery for it. Then, multiple HBA/RAID cards from different vendors in the same system are not going to work stable. More then, with a different size drives, no common RAID scheme can be applied. Should the RAID fail, the system is not recoverable. OK you can go with ZFS hybrid filesystem-RAID capability, but it is even less recoverable when failed. On top of that, this borderline weird configuration was never tested. The symmetric configurations with md-raid and ext-whatever used in stock NAS units like QNAP are at least well tested and understood (and still even these have problems)

So, what comes of it - stick with simple and standard configurations. The increase in efficiency for a unique build is small and is not woth the problems you encounter when it fails.

Friday, 7 October 2011

Remote recoveries

Every once in a while we do a remote recovery session via TeamViewer. The most annoying thing in remote recoveries actually is not knowing who is in control. TeamViewer does not provide any feedback when the other party is going to take over by pulling a mouse cursor away.

The fact that someone is standing on the remote side watching what you doing, and you cannot even tell if they are there or not, is not very comforting but acceptable. With remote recoveries, it is a part of a job, actually. Someone may choose to ride the shotgun with you.

The real problem starts when they interfere with what you are doing and there is no way to stop it. This is not really because people on the remote side are specifically evil, just because there is no convenient way to establish who is in control, and how to request or how to relinquish it. Damn annoying still.

Thursday, 6 October 2011

Windows Update Error 80072ee2

This comes unrelated to the data recovery, but still it did cost me about two hours of time.

If you have a Windows Update Error 80072ee2 on a freshly installed Vista, install Internet Explorer 9 manually. Btw, installing SP2 does not help.