How can I connect a SAS drive to USB?

Question

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...

Solution 1

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.

Solution 2

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.

Solution 3

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.

Solution 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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Comments

[pauska]

That drive can hit up to 16 watts of power usage.. I would not trust that USB adapter to maintain that kind of load.

[Lucas Kauffman]

considering the price of a SAS drive and the target customer, it doesn't really surprise me that there aren't any USB adapters around for it.

[John Gardeniers]

It would appear you are not fully conversant with the concept of backups.

[dave]

@pauska - the SATA adapter has a 2amp power injector.

[dave]

@JohnGardeniers - the data is backed up nightly and off-site (although admittedly not mirrored). If the Dell T710 dies some hours after the backup, I need to patch the live journal file from the dead T710 onto one of the backups. But how do I read the SAS disc containing the journal?

[dave]

@LucasKauffman - okay, so imagine I have an SAS disk in my hand. What IS the cheapest way of reading it?

[Lucas Kauffman]

@dave computercablesource.com/…

[Dave M]

+1 for backup rather than "Rube Goldberg " device

[EEAA]

@DaveM But Rube Goldberg devices are FUN! :)

[dave]

@ErikA - thanks for your input. The data is backed up nightly and off-site (although admittedly not mirrored). If the Dell T710 dies some hours after the backup, I need to patch the live journal file from the dead T710 onto one of the backups. But how do I read the SAS disc containing the journal?

[dave]

@ErikA - just to answer your 'asides', I think these are dealt-with thanks to the periodic off-site backups. The specific scenario I am trying to cover is when the SAS disc is fine but the Dell T710 (for whatever reason) will not read it. (Maybe the T710 motherboard is broken; maybe Windows won't boot). I need a way of reading an SAS disc that does not depend on the only SAS-capable machine I have to hand.

[northben]

I need to RMA a SAS disk, and would definitely prefer to wipe it first. I may get a SAS to SATA adapter for this purpose. If a laptop had an esata connector, it may help in your scenario too.

[dave]

Excellent; concise and on-subject; thank you for this clear explanation of why this isn't working

[x-x]

So why do these adapters even exist?

[dave]

Wow, thanks for resurrecting this old post to add this great answer - I wish this product had existed at the time! I'm sure this answer will help people who find this post via internet search.

[Roy]

Please note that this answer, while correct in 2016, no longer holds true. There is now a range of inexpensive hardware available, that will connect SAS over USB. Not that it matters, most of my servers now use NVMe.

[Admin]

Because some SAS host controllers are dual function: SAS and SATA.