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dave
Asked: 2012-04-05 11:42:39 +0800 CST

How can I connect a SAS drive to USB?

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I have a Dell T710 with Seagate Cheetah 15k.7 SAS disks. If the T710 motherboard dies, I'll need to resort to one of my nightly off-site backups and salvage the journal/logfile from the SAS disk to bring the backup bang up-to-date.

I need a way of reading the healthy-but-inaccessible SAS disc that does not depend on the only SAS-capable machine I have to hand.

So I bought:
SAS to SATA Adapter
and:
USB 2.0 to SATA Adapter with Power
...so that I could read the SAS drive via USB.

I can plug it all together just fine. The chain looks like: USB -> SATA -> SAS. But the drive does not spin up and the computer doesn't even acknowledge anything being attached by USB.

Is there a cheap external enclosure I can buy for SAS drives? I can't believe these USB to SATA adapters are everywhere but the USB to SAS adapters are almost non-existent...

hard-drive sas scsi adapter drive

4 Answers

  1. Your SAS to SATA adapter isn't a protocol translator, just a pin to pin adapter. It won't let the USB to SATA adapter speak to the SAS drive in any language other than SATA... which it won't support. So you won't see anything happen.

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  2. SAS is largely a server technology whereas USB is most definitely not (at least as far as storage goes, anyway). I'm guessing this is why you haven't found any suitable adapters.

    That said, you're going about this the wrong way. With a good backup regimen, you dont need the original hardware. So, get a good backup system in place and this issue is resolved.

    As an aside, your proposed solution (USB SAS enclosure) only protects against a very small subset of failure modes. How do you propose you'd recover in the event of:

    • fat-fingered command that deletes a bunch of data
    • RAID card nastiness that corrupts data
    • theft
    • disk failure
    • nuclear fallout

    To recover from these, you need a real backup solution, and preferably one that moves data off-site.

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  3. Best Answer

    Such device finally exist CXRT SAS to USB adapter CXRT-USB3. You can find it on Amazon, eBay and couple other places. There are 2 downsides in my opinion. It’s almost 100 times more expensive than cheap SATA to USB, around 700$. And it supports only SAS, not SATA so you may need to carry multiple devices.

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  4. While we can all appreciate the occasional advice on backup strategies and their importance, there are things that even Tivoli won't help you with, so to answer the actual question, in short:

    To retain the ability to access your SAS drive in case of workstation-failure, the best option is likely another workstation.

    Here is why:

    SAS is a costly addition when you consider it's not terribly useful in workstations and as such is not a feature commonly offered. Even so, as some of these machines are based on server chipsets, Dell apparently found it convenient to re-use planar designs from their line of commodity servers, which include a low-end integrated SAS/SATA RAID-controller.

    The result is that Dell Precision workstations are, in fact, one of the least expensive ways I have found for connecting SAS drives outside of the server room.

    Compared to external enclosures with an integrated controller, you get a workstation for free. Even compared to an aftermarket internal PCIe controller the difference is not that much, and adds the benefit of being a tested and supported configuration.

    Other use cases include forensics, diagnostics and p2v conversion.

    Even as I write this I have two T7500 workstations under my desk that are chirping away at SAS drives that are in the process of becoming virtual disk images.

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