Musings of a PC

Thoughts about Windows, TV and technology in general

Things I’ve learnt about the DS351

As I wrote recently, the Silverstone Technology DS351 external storage unit connected to my HTPC recently misbehaved in that no drives were being presented to the computer, either at the BIOS level or at the OS level.

Yesterday, I managed to get everything back as it should be so I thought I’d document what I learnt along the way in case any of this is useful to anyone else.

I had written in the previous posting that the enclosure had five drives, three set up as a RAID 0 array and two as a RAID 1 array. My initial thinking was that I’d disconnect one of the mirror pairs from the storage unit and plug it into my Dell Precision workstation as a standalone drive and copy the files off it that way.

The good news is that that worked. Windows Vista was happy to read the drive without any problems and I soon copied the data off that drive onto another one for safe keeping.

Now to the three-drive LUN. As my Dell workstation only has one spare SATA socket, my initial thinking was that I’d have to buy an additional PCI card to provide further SATA sockets, connect the three drives up and then use a third party tool to recover a broken RAID 0 array. I had done some research on the sorts of tools that are out there but hadn’t reached any solid conclusions. Most, if not all, of them allow you to download the software first so that you can use it against your drives to see what it will find. However, they won’t allow you to actually recover anything without buying a licence.

As it turns out, though, none of this was necessary.

In preparation for getting one of the mirror pairs into the Dell, I pulled up the configuration tool for the Silicon Image 4726 to confirm which drives were in which LUN. It was then I discovered – or remembered – that the three drives were not set up as a RAID 0 array. Instead, they were set up as a spanning volume. In other words, instead of the data being striped across the drives, the logical LUN is built from the three drives concatenated together. This gave me the thought that – if I was lucky – I’d be able to plug the first drive of the LUN into my Dell and all of the data would be on that first drive.

It was.

Phew would be an understatement. I quickly set about copying the data off that drive onto additional external drives for safe keeping. Once that had been done, I put all of the drives back into the DS351, screwed it together and reconnected it to the HTPC.

Um … now the configuration management tool won’t see the DS351. A couple of reboots later and it dawns on me that the Device Manager interface in Windows is showing that the SATA controller is missing its driver for some reason. A quick install and we’re back in business – the tool can now see the DS351.

As I’d copied all of the data off the drives, I decided to go a different way with the LUNs. I didn’t want to repeat the scenario where I might not be able to re-create the logical setup in order to recover the files. I was happy with the mirrored pair so I’ve kept that but I’ve now configured the other three drives as separate LUNs. That way, if a single drive fails, it won’t take the whole lot with it and if the RAID controller fails again, I have a smaller headache to deal with.

Having reset the LUN configuration, I expected that to be the end of it … except that it wasn’t. The drives didn’t appear. Just as I was beginning to think that the RAID controller was broken for good, I realised that in my previous attempts to restore normal working, I had overlooked one opportunity – to reflash the firmware on the 4726 itself. I’d updated drives and the BIOS for the SATA adapter but I’d overlooked the 4726. About 30 seconds later … and the drives appeared!

What was interesting at this point was that even though I’d reconfigured the LUNs, the data had been left intact. This is good to know for the future! All that was left was to move the data off the original “first drive” onto a standalone drive so that I could re-initialise the drives. This was required because the drives seemed to have been configured by the 4726 in order to support the spanning LUN.

So it is all done and dusted. Data all there and LUNs in place. I could have done without the stress, though!

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