mini-SAS on Thunderbolt?

[Brad Bussé]

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.

[Chris Murphy]

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.

[Brad Bussé]

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!!!

[Chris Murphy]

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.

[Nick Kustreba]

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.