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mini-SAS on Thunderbolt?

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Brad Bussé
mini-SAS on Thunderbolt?
on Sep 4, 2013 at 8:45:11 pm

I'm upgrading another "new" Mac Pro and need to get an external RAID. Knowing that the new Mac Pro release is imminent, and the new platform will have TB ports but no internal PCIe slots, I'm not sure if I should invest in a large RAID now or just get something to last long enough to get me to the point where I'm ready to switch over to the new Mac Pro platform with a TB RAID.

So, my question is this: if I invest in a nice large RAID solution now, will I be able to run it reliably on a future Mac Pro by running it via an external PCIe expansion plugged into Thunderbolt? Anyone doing this now on an iMac or Macbook Pro?


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James Cude
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 12:29:19 am

If a new Mac Pro is in your future- it would make more sense to plan for a Thunderbolt Raid i.e. a Pegasus and get by with something else for now that you could reuse such as a drive with both USB and Thunderbolt. GTech makes such RAIDS. PCI to Tbolt is an option but probably not as solid of performance.


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Brad Bussé
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 12:36:00 am

I thought that USB was no good for video work due to an inherent latency. Has that changed with USB3?


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Jeremy Garchow
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 1:05:06 am

What raid and controller specifically?

If you buy smart, you'll be able to move your PCIe HBA to something like a Sonnet Thunderbolt PCIe enclosure, allowing you to get more work done now, rather than wait.

I am planning on doing this very thing once we need TBolt connectivity through new MacPros or other CPUs.

Jeremy


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James Cude
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 5:42:15 am

Yeah but why bolt on PCI to Thunderbolt if you don't have to- all that extra gear, cabling, power needs etc.. Sure it works for older legacy gear but unless you're planning on blazing through 1080p uncompressed, something like this makes more sense:

http://www.g-technology.com/products/g-speed-q

You get FW800 for the older Mac Pro and with eSATA you could easily go USB3 to on the new Mac Pro.


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Jeremy Garchow
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 12:26:17 pm

It all depends on how much storage you need and how fast you need to go.

The pcie enclosure will allow the utmost in flexibility as you can always add cards to it later.

It would allow Brad to get to work now and not worry about a future CPU purchase.

Thunderbolt is gobs faster than fw800, esata, and even usb3, as is mini sas.

It really depends on what brad needs to do. The pcie enclosure will require one more power cable, and a thunderbolt cable, it's not the end of the world.


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Chris Murphy
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 1:09:35 pm

I agree that the PCIe expansion chassis is not elegant. This whole Thunderbolt thing strikes me as benefitting Apple first, and customers second in that at least we're getting some ability for high speed connectivity rather than none, because Apple long ago decided to be done with traditional desktop hardware. But this is what's available, so if you want to use OS X the Thunderbolt to PCIe enclosure is the new paradigm unless/until companies come up with a totally different form factor for their products that directly connect to Thunderbolt as the primary interface rather than effectively being adapted to a PCIe slot.

The alternative is go Windows or Linux for video work. *shrug*

Anyway I don't think the G Speed Q meets the OP's requirements if he's considering mini-SAS.


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Jeremy Garchow
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 1:16:23 pm

[Chris Murphy] "This whole Thunderbolt thing strikes me as benefitting Apple first, and customers second in that at least we're getting some ability for high speed connectivity rather than none,"

Again, how fast do you need to go?

Thunderbolt is plenty capable for most users, and can support multiple people editing off of the same array.

It is much faster than fw800, esata, and usb3.

It's 10Gb/sec in one direction. Isn't 10Gb fast enough?


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Marcus Moore
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 1:39:47 pm

[Chris Murphy] "I agree that the PCIe expansion chassis is not elegant. "

Absolutely. But let's be clear about the use-case for PCIe in the new MacPro- the VAST MAJORITY of people will be using it to connect to legacy hardware that they're not ready to give up yet. But in the last 2 years most of the major manufactures have started offering TB connects for their products, so it's not like a PCIe expansion chassis is going to be perpetually necessary in this scenario going forward. Some will continue to need it for a while, but those use-cases will become less and less.



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Jeremy Garchow
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 4:07:10 pm

[Marcus Moore] "[Chris Murphy] "I agree that the PCIe expansion chassis is not elegant. "

Absolutely. "


Let's back up a minute here.

What about PCIe, in general, being 'inelegant'?

Working on anything PCIe is a jammed up mess. You are cramming stuff into a really heavy computer, you are putting together little tiny connectors in the back of an already crowded computer, usually in to a recessed cavity. Thunderbolt, at the very least, allows you to place those components where it is most convenient, and allows you to take anything apart and remove something without disassembling or moving a big heavy box, which in turn, allows you to keep working even when one PCIe extension isn't available.

What you see as a negative, I actually see as a positive, but then again I have more than one machine to attend to.


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Chris Murphy
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 1:00:47 pm

If you built a large array with something, e.g. from ATTO, it should work in a Thunderbolt -> PCIe enclosure. Should. Without someone testing, it's unknown, but someone will test it and I'm reasonably certain if there are problems found that they'll get sorted out. The alternative scenario is just too close to a horror show for video on the Mac - let's face it.

I think the question is, are you needing to actively use a large array now? If you can make good use of it now, then I'd get it now and worry about the compatibility with the next machine later. If you don't really need it now, then the question is what to use as a stop gap.

With any "large" RAID my concerns are: drive quality and raid card options. That you're thinking mini-SAS implies SAS drives which tend to be nearline or enterprise and are more reliable than consumer SATA, and that goes a long way to reduced urgency for using a more resilient file system than HFSJ. Better drives don't totally obviate my HFSJ/NTFS concerns, but it accounts for a lot. Next, whatever raid card you get should explicitly support scrubbing, some of the raid products clearly don't. You want to scrub the array probably once a month. I know people who do it weekly.

Another way to get around this is look at a non-Mac host for big storage that's available via 10GigE, and then you can have new and old MacPro that can share the same storage, should you desire an extra workstation which could be useful for transitioning to new hardware. It's more than a bit more complex since you have all the storage concerns with direct attach, but you also have network concerns, and both have to be done right for network storage. But once it's working, you walk away from it until something dies. It isn't affected by OS updates causing conflicts with drivers, you can concurrently use it with more than one computer, you can pick a file system that's as good or better than HFSJ or NTFS.

So I'd state how big you want the storage to be, what your usage is going to be and hopefully some people with more experience respond. I'd also plan on calling some companies who sell and support such storage, get quotes, and then you'll be in a better position to make a decision.


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Brad Bussé
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 6:34:52 pm

Thanks for all of the replies. Although I'd love to utilize something more modern and robust than HFS+, I'm sticking with that for the time being.

My workflow is primarily ProResHQ 1080 60p with ProRes4444 for alpha. I've actually worked off of one of the 4 drive GTech units in RAID-5 connected via e-SATA. At the time I was mainly ProResHQ 1080 24p and it worked okay, but certainly it wouldn't hurt to have something better than e-SATA. I don't have to have tons more space than the 6 TB available after formatting - I suppose that could be one year out from now, so perhaps this ultimately will be a stop gap measure, but I just want to make sure that I'm not stuck with an interface that will be too limiting. For this reason and to keep costs down, I was looking at starting with a G-Tech unit utilizing mini-SAS. That way I'm not worried about bumping up against the limitations of eSATA now, and I have the option of trying to add it as a TB-PCIe expansion to a new Mac Pro down the line without being forced to upgrade the array right off the bat to a larger TB native array.

Regarding USB3, is anyone using this for connecting an external RAID array for video work? Did they address the latency issues with USB in the upgrade to USB3? That might be an option since the new Mac Pro will have USB3 conections and they can easily and cheaply be added to the current Mac Pros via a PCIe card.


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Chris Murphy
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 9:06:29 pm

certainly it wouldn't hurt to have something better than e-SATA

For what it's worth G-Speed Q is a particular instance of eSATA that uses the SATA Rev 2.0 spec, or 3Gbps. When considering the G-Technology unit that uses mini-SAS, its ExpressSAS R680 card is 6Gbps SAS. So it's a different interface, command set, and bandwidth. I haven't benchmarked the workloads you're talking about to see if there's a meaningful difference between SATA 6Gbps, and SAS 6Gbps, so I have to defer to others. But if SATA, for sure specify at least nearline if not enterprise drives. It's not worth the hassle factor with consumer drives and incorrect (and usually unconfigurable) error recovery settings that inhibit proper raid5 bad block repair.

Check the R680 card if it has a scrub option. In my opinion, scrubs are mandatory functionality. My own personal bias is to disqualify a product that doesn't offer it. I might even go so far as to disqualify on the basis of being unable to have regularly scheduled scrubs, with an email in case of mismatches occurring. I'd seriously rather go with a simpler solution like raid10, or even two independent raid0's and a daily rsync from one to the other than mess around with junk raid5 that doesn't have a proper scrubbing function. "Wow cool, I have raid5 but no scrubs," is buying into fail safe that has a decent chance of fail danger rather than fail safe. Why bother? You shouldn't have to wonder whether a raid5 rebuild is actually going to succeed.


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Brad Bussé
Re: mini-SAS on Thunderbolt?
on Sep 5, 2013 at 11:16:59 pm

Thanks for the information, Chris. I don't recall the G-Speed Q having scrubbing as an option, though I can't be sure. Previous to that, I had worked with an X-RAID that was set as RAID-50. I don't recall scrubbing being in the tools there either, though it had a couple options for diagnostics that checked for errors so perhaps one of those was scrubbing. Good info to know for those of us with RAID-5 arrays!!!


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Chris Murphy
Re: mini-SAS on Thunderbolt?
on Sep 6, 2013 at 11:10:40 pm

Xserve RAID has two options: verify and rebuild parity. Verify reads data and parity chunks, and reports mismatches. Rebuild reads data chunks and writes new parity chunks. Verify is the one to use regularly, there's no good reason to rebuild parity without a specific reason. Verify is sufficient to activate any needed self healing as a result of bad sectors.


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Nick Kustreba
Re: mini-SAS on Thunderbolt?
on Jan 27, 2014 at 7:16:55 pm

Hi all-- Nick from ATTO here, both the R680, R380, and 3808D can do parity verify and repairs and you can schedule them on whatever basis (daily, weekly, monthly, every sunday at 2 AM, etc -- your choice) you want using our GUI Configuration Tool. If you have any other questions, please let me know.
Thanks.


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