Thunderbolt 1 vs Thunderbolt 2 real life speed

Discussion in 'Mac Pro' started by juanm, Jan 9, 2014.

  1. juanm macrumors 65816

    juanm

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    #1
    Hi

    I'll soon be buying a new Mac Pro. I've been considering storage alternatives, and have been offered a Pegasus R4 with Thunderbolt 1 (the newly released Pegasus2 sport a Thunderbolt 2 connection)

    The Mac Pro has Thunderbolt 2. Is there any real life speed difference to expect between the Pegasus and Pegasus2 systems?
    I'll be using it for Full HD prores or 2.5K Blackmagic RAW footage.
     
  2. Bear macrumors G3

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    #2
    Are there SSDs or HDs in the Pegasus - if it's HDs there will be little to no performance difference.
     
  3. juanm thread starter macrumors 65816

    juanm

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    #3
    Old fashioned spinning HDDs. I wish I was offered this deal on a Pegasus filled with SSDs! :p
     
  4. mintakax macrumors regular

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    #4
  5. deconstruct60, Jan 9, 2014
    Last edited: Jan 9, 2014

    deconstruct60 macrumors 604

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    #5
    " ... Performance
    When I tested the original Pegasus R6, it was by far the fastest external storage device. Now the Pegasus2 R8 has almost double the speed. ... "

    Almost none of the differences here have primarily to due with TB 1 or TB 2. First it is a 6 vs 8 sled box. ( apple-to-oranges point one). There appears to be a RAID controller change. ( apples-to-orangles point two ). That whole chart in performance fits well inside of TB v1's boundaries.

    376 MB/s ---> ~3Gb/s
    210 MB/s ---> ~1.7Gb/s

    4-8 reasonably affordable HDDs aren't going to make a big difference to either version of TB except perhaps in some very limited corner cases (e.g., single large file sequential reads ).

    The issue far more is what else is on that TB controller's daisy chain(s) they have to share bandwidth with. ( or don't have since have three "TB bus" available in a Mac Pro. )


    2TB drives versus 1TB drives... Yes, the 2TB ones are more expensive. Not particularly strange in that set of contributing costs.
     
  6. juanm thread starter macrumors 65816

    juanm

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    I might be wrong, but I think this is due mostly because of the amount of hard drives it's writing on/reading from, not the bus itself. Similarly, R6 was faster than R4.
     
  7. Luba macrumors 6502a

    Luba

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    Apr 22, 2009
    #7
    TB2 bus 0 on nMP has HDMI 1.4, and the bottom two TB2 ports (commonly named port #5 and #6), does that mean 20Gbps is shared with those 3 ports?

    I thought each TB2 port had a bandwidth of 20Gbps each way??

     
  8. joema2 macrumors 65816

    joema2

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    #8
    Exactly right. I have an 8TB TB1 Pegasus R4 in RAID 5 (6TB formatted capacity). It does about 858 megabytes/sec read, nearly 700 megabytes/sec write. See attached benchmark. In theory that is about 7 gigabits/sec. That is on a 2013 iMac 27, i7 @ 3.5Ghz, 32GB RAM, 3TB FD, GTX-780M.

    If those same 4 x 2TB drives were plugged into a TB2 enclosure and connected to a TB2 port on a nMP, it probably wouldn't be any faster.

    However it appears to be using 70% of the TB1 channel bandwidth, so if you had an even faster SSD RAID array, maybe it would bump against the TB1 limit. Likewise if you wanted to daisy-chain more fast TB devices on that same string, it would be limited.

    However the nMP has *six* TB2 ports available. If you got a good deal on a TB1 Pegasus R4, you could easily dedicate a port to that.
     

    Attached Files:

  9. deconstruct60 macrumors 604

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    #9
    The HDMI port uses zero Gb/s of the Thunderbolt network. None.
    Neither do any host connect DisplayPort devices.


    It does for traversing the TB network. The bandwidth to the host is another story. The 20Gb/s is for passing data along the TB network. That doesn't mean all of it can be basting into a single host computer.
     
  10. Luba macrumors 6502a

    Luba

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    #10
    Thanks for clearing up how TB2 bus 0 works!

    But still unclear about bus and port. If each TB2 port can handle 20GB/s of data each way, does that mean the bandwidth of the bus is 40Gb/s each way since there are two TB2 ports per bus?

    Lastly, I read somewhere that you can't or shouldn't connect two 4k displays on the same bus, so you have to remember to connect the displays to say, port #1, #3, and #5.

    I don't understand what you mean: Displays don't use the data of the TB network, so daisy chaining an external storage device off a 4k display doesn't take away any GB/s for the external storage device?

    Thanks for answering my questions. :)



     
  11. juanm thread starter macrumors 65816

    juanm

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    Wow! :eek:
    Which brand or model of hard drive do you have in that R4?

    I'm still debating whether I should get a an iMac exactly like yours, or the new Mac Pro (the sole reason I'm currently leaning towards a Mac Pro is 4K support for down the road).
     
  12. joema2 macrumors 65816

    joema2

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    #12
    4 x 2TB Toshiba DT01ACA200; it's a 3.5", 7200 rpm 6 gbps SATA drive with 64MB internal cache. It's 8TB unformatted, about 6TB formatted for RAID 5.

    If you get an R4 be advised the initial RAID 5 sync can take quite a while. If you select the default stripe set of 128kb it can take days. This is easily corrected if you know to do it. See my performance tests and graphs here: http://forums.macrumors.com/showpost.php?p=18576138&postcount=1

    That is a tough call. You can view and edit 4k video on the iMac, just can't view it full-screen pixel-for-pixel. By 4k if you mean a 4k display purely for screen real estate, it's probably cheaper to have an extra 27" TB monitor on the iMac.

    From a CPU perf. standpoint, I'm not sure the quad-core nMP is much faster than a max'd out iMac. The GPUs are faster, and some highly specific software might take advantage to a degree that's readily apparent.

    OTOH if your video editing or transcoding software uses Intel's "Quick Sync" instructions, some Xeon CPUs don't support this. In some cases Quick Sync can be 5x faster at transcoding than other methods, but only for a few codecs.

    The first nMP with the potential to be generally faster is the six-core, and that's considerably more money, esp if equipped with 32GB/512GB SSD + 27" display (equal to the top-end iMac).

    However the nMP (even the quad-core) is more expandable and available with 2x the RAM and 2x the SSD of the best iMac. If I was doing 4k video editing all day long and I could afford it, I'd get a nMP.
     
  13. deconstruct60 macrumors 604

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    #13
    Only if double counting. TB controllers are switches. It is far more so bandwidth across the switch.

    TB-dev1 < --- 20 Gb/s ---> TB-dev2 <---- 20 Gb/s ---> TB-dev3

    If TB-dev1 wants to pass 20Gb/s of data to TB-dev3 then one port of TB-dev2 has to take in 20 Gb/s and the other port has to output 20 Gb/s. It is the same data coming in and going out. That is the max bandwidth of TB data that is being specified. The only way to "max blast " a TB port is to use another TB port.

    At any one specific target the 'freeway' off ramps are x4 PCI-e and DisplayPort 1.2. If only offloading only one of those at the destination, you are going to be extremely hard pressed to get 20 Gb/s "off the freeway". The single off ramps are not as 'wide' as the freeway; nor should they be.



    Actually #1 and #3 are on same TB bus.

    http://support.apple.com/kb/HT5918


    Apple's directive is not to hook more than 2 monitors to a single "TB bus". Pragmatically the 4K monitor is going to count as at least 2 ( since 4 x HD resoution dimensions). The DisplayPort bandwidth to each "TB bus" is likely limited. Three 4K monitors probably means something like #1 , #2 and either HDMI , #5 , or #6.

    By "Thunderbolt Bus" I think Apple means the two type inputs ( PCI-e and DisplayPort there are multiple, but finite, DP signals coming in ) and TB controller in combination.


    When you hook a DisplayPort device to a host computer the TB controller is effectively bypassed. The "backward compatibility" is more pragmatically a "by-pass" mode. The DisplayPort signal is never encoded into TB protocol and never put on the TB network. It is put directly on a DisplayPort network. On the port with the DisplayPort device plugged in there is no TB traffic at all. Hence TB bandwidth consumption is zero. DP bandwidth is non zero, but that isn't TB bandwidth. The bandwidth maximums on that "by-pass" to DP port are going to be DP's maximums not Thunderbolt's.


    If you daisy chain so that the DisplayPort device is on some external , downstream device than the DP traffic is encoded into TB traffic and moved to that last TB device. At point it is decoded back into DP data. On that device's output port it is just DP data going out. But it came in as encoded TB data on the other port.

    However, if start at the host there is zero transport done. No transport. No TB bandwidth consumption.

    Similarly with the HDMI port. More than likely the DisplayPort signal is diverted before it ever gets to the TB controller. Pretty sure there is next to no good reason to even send it there at all.
     
  14. analog guy macrumors 6502

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    #14
    thanks for taking the time to break that down. i appreciate it.

    so, if i understand your explanation, if one has 3 display port monitors and 3 thunderbolt enclosures, the highest performance configuration would be one display port monitor and one TB enclosure on each of the 3 TB buses, correct?

    in this way, each enclosure would have the maximum 20GB/s available to it, correct?

    instead, if one daisy-chained each DP monitor off of the thunderbolt enclosure (with each pair on a separate bus), then the DP-signal-converted-to-TB would rob some of the available bandwidth to the TB enclosure.

    did i get that right?

    thank you!
     
  15. Djreversal macrumors newbie

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    Nov 16, 2007
    #15
    Raid 0 would offer even more speed.. probably more along the lines of 900mb/sec i would think.

    The good news is, if this is around 9gbps then u can daisy chain 2 of these devices on 1 Thunderbolt port and effeciently use the full bandwidth.. i plan on running 2 Pegasus2 R4's. Possibly a 1gig Lacie big Disk for my direct drive for editing since its dual SSD's run around 1300mb/sec which will help in 4k editing alot.


    I get my Macpro / Pegasus Monday... I cant wait.
     

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