Noob question. Can I use an empty hdd bay as a sata power source? [solved]

Discussion in 'Mac Pro' started by Korican100, Aug 3, 2013.

  1. Korican100, Aug 3, 2013
    Last edited: Aug 4, 2013

    Korican100 macrumors 6502a

    Korican100

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  2. omnious macrumors member

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  3. Korican100, Aug 3, 2013
    Last edited: Aug 4, 2013

    Korican100 thread starter macrumors 6502a

    Korican100

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    #3
    on the same note, could I use that SAME bay's SATA data slot on via sata to esata cable connected to a externall powered HDD?


    So basically one HDD sata bay is powering a pcifan card, and receiving data from an externally powered HDD?
     
  4. flatfoot macrumors 65816

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    #4
    Yes, that'll work, too. But that port isn't hot pluggable, i.e. the external drive can't be turned off while the Mac is running.
     
  5. flowrider macrumors 601

    flowrider

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    #5
    ^^^^Why Not? If you drag the drive to the trash and eject it, why could you not then turn it off?

    Lou
     
  6. Korican100 thread starter macrumors 6502a

    Korican100

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    #6
    what happens if it does get turned off? and can you leave an external drive on all the time? (don't they automatically "sleep" anyway?)

    if its connected via HDD bay, would it be read as an internal drive? Can you eject internal drives? can someone confirm?
     
  7. glutenenvy macrumors regular

    glutenenvy

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    #7
    To maximize the life of your equipment you need to minimize any actions that cause a power surges or sparks. Unless you are working with specifically hot swappable interfaces, you should not be connecting or disconnecting internal cables while the machine is on.

    The question then becomes, "How long will it work?", when you take part in electronically risky behavior.
     
  8. Tesselator, Aug 4, 2013
    Last edited: Aug 4, 2013

    Tesselator macrumors 601

    Tesselator

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    #8

    You should be able to turn it on and off using that cable as a power source but you would of course need a switch in-line. The problem might be the DC developed potential difference during short (like a surge when you switch it on) but I dunno how critical that would be - because I dunno what the circuit looks like. The machine certainly powers up those drives when you turn it on. :) If you're afraid and just have to switch it independently then you could build a circuit using a fairly big cap with a resistor in series and then switch across the resistor. Search to find some DIY electronic sites or discussion forums and ask them how to build such a thing. There's a lot of helpful folks out there.

    As for sleep this is sent as a command to the drive over the data cable so if the drive supported it (I guess all do) then you could tell it to sleep and it would.

    Internal drives can indeed be ejected or unmounted. Not the boot drive tho.

    To be seen as an internal drive the drive's data cable would need to be connected to one of the backplane or AUX SATA connectors. It doesn't care where the power is coming from. For example you could connect SATA data cable from the internal backplane to the drive and power it from an external source and the OS would see it as being an internal drive. This doesn't work in reverse however: Just because a drives uses the power from the backplane doesn't mean the OS will see it as an internal drive (unless the data connection is from one of the internal connectors as well).
     
  9. Korican100 thread starter macrumors 6502a

    Korican100

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    #9
    hmm i have no idea where to start so that will definitely take a lot of research on my part.


    well then theoretically, couldn't I just leave the drive 'on' all the time. The drive is my a "backup/time machine" drive.


    thanks for the good info

    ----------

    so I could just leave the external drive "on" all the time? its a time machine/backup drive
     
  10. ColdCase, Aug 4, 2013
    Last edited: Aug 4, 2013

    ColdCase macrumors 68030

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    #10
    The external HD will work just fine. The MP recognizes drives connected on the internal drive ports only during boot, however. Recognizing drives real time is the hot swap feature. ..edit.. newer firmware may not nee a reboot, but the drives would need to be mounted manually (via disk utility, terminal or third party app.)

    So if you eject the drive, you will have to reboot the machine to see it again. If you don't eject and just pull the cable (or turn the external off), you get the OS warning that the drive was not disconnected properly. Plug the cable back in and the OS will re-mount the drive as it remembers it from the boot process.

    I do something similar routinely. I have a couple external drives in an eSATA enclosure. When I put the MP to sleep I turn the drive enclosures off to quiet the fans. Upon wake I get the warning, but the warning disappears when I turn the enclosures back on. There is nothing going on to damage the files or directory while the MP is sleeping.

    The internal drive ports are not eSATA, they are not designed to be routed outside the box nor withstand many insertion cycles. It will work reliably when using high quality SATA cable in short lengths. I would not go over a meter total length, but YMMV. I would not put a lot of mechanical stress on the internal ports, it is better to connect the internal ports to a mounting plate where you can connect the eSata cables to your drive. These are pretty cheap.

    Something like this:

    http://www.newegg.com/Product/Product.aspx?Item=N82E16812186179
     
  11. flowrider macrumors 601

    flowrider

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    #11
    I certainly agree about not disconnecting internal cables. however he's talking about an external drive, so I see no problem here.

    Not really, you can go into disk utility and remount again it from there.

    Lou
     
  12. ColdCase, Aug 4, 2013
    Last edited: Aug 4, 2013

    ColdCase macrumors 68030

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    #12
    On early machines, the firmware does not present the ports to the OS unless there is a working drive attached. There is no mechanism for the OS to rescan the ports.The machine's disk utility would not ever see the drive. Sleep works OK as the OS remembers the drive was there regardless of what the firmware is telling it :)

    So, it depends on the machine, worst case it is a reboot, along the line somewhere the firmware was revised perhaps. Best case is a Disk utility or terminal command, I think some third party apps like Jettison may also work.
     
  13. Korican100 thread starter macrumors 6502a

    Korican100

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    #13
    ok guys just to recap, because this has been a whirlwind of information:

    I have One HDD bay SATA powering an internal pci fan card, AT THE SAME TIME getting data from an externally powered HDD in an enclosure.

    So I should make sure the HDD is powered on before I turn on my MacPro.
    Don't poweroff/disconnect while the Macpro is on
    If I do disconnect, then reboot/or use disk utility (this is currently being discussed)

    Again, is it ok, just to leave the HDD on at all times, then I won't have to worry about turning it on before, or disconnecting it? The HDD goes to sleep when not in use correct? I don't think this should be an issue then, but confirmation would be awesome.
     
  14. Tesselator macrumors 601

    Tesselator

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    #14
    1. That will work fine. A fan doesn't draw too much power.
    2. Probably. Try it once the other way and you'll know for yourself.
    3. I see now you're powering the drive from an external power supply so there is no harm at all in turning it on or off as you wish - if the OS isn''t writing to it or anything. SOP is to eject first however and this is wiser.
    4. Don't disconnect it. Use the Eject or Unmount commands and then power off as you wish.
    5. Sure, you can just leave it on. If you want it to stay asleep don't use it for any OS stuff like home folders, mail, or anything that will access it. Accessing it through software will spin it up again. Sometimes a condition can be created where the drive is spinning up and down many times a day and that's not too good for the drive. Time Machine will spin it up too I believe.
    6. If you set it to do that then yes.
     
  15. Korican100 thread starter macrumors 6502a

    Korican100

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    #15
    Thanks so much man. You've really helped me today with some purchasing decisions. Thanks thanks!! And thanks to all in the thread!!
     
  16. orph macrumors 6502a

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    #16
    your safer & easier with sticking your internal drive in to an usb/fire wire/esta box.
    as a time machine drive you can live with slower speeds, and lower risk of braking stuff.

    what about a HD in your spare optical slot ? (if you have one)
     
  17. Tesselator, Aug 4, 2013
    Last edited: Aug 4, 2013

    Tesselator macrumors 601

    Tesselator

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    #17
    This is correct. If it's for TM then the Mac Pro's USB is fine - fast enough to not make a noticeable difference in all but a few extreme cases.

    If it's for TM don't use the optical slot tho - not enough cooling and it breaks the rule of backup being better externally connected.

    Also if it's for TM then I would recommend using one of those open drive-docks. This way it's easy to keep one extra backup on a shelf or at you mom's house - a recommended and inexpensive practice. If you get a USB3 drive dock then when you move it to a machine with USB3 (or buy a card for you MacPro at $25) it'll actually be faster then the SATA II you'r trying to use now.

    SATAII = 300 MB/s
    USB3 = 500 MB/s
     
  18. orph macrumors 6502a

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    #18
    if it is time machine over night updates is a nice work around.

    (i dont like messing with stuff :apple: im scared of braking stuff, all i know is it's stuff to brake so i dont touch it.) :p

    and just thinking how you will mount & power a drive outside the computer so it's safe is a pain just having it on the floor/table is not a good idea i assume.

    ps as an 'internal' drive it will, i assume behave like an internal drive so it will not show up like a usb which you can just eject you will have to use disc utility etc.
    as a back-up/TM drive it sounds like a lot of extra risk to your data.
     
  19. orph macrumors 6502a

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    #19
    i like the look of the external USB3 mounts, but never been shore how to store the drives that are not in use, are they ok bare or do they need a box?

    keep the hover away i assume :rolleyes:
     
  20. Tesselator macrumors 601

    Tesselator

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    #20
    1. You can run a bare drive no cradle, no enclosure on a clean tabletop if you never spill anything (including your box of metal paperclips) around it and don't bump it around - that's fine. If you're working it hard open like that then a $5 USB fan blowing across it is recommended. A very weak airflow is all that's needed.
    2. You can "eject", "unmount", or "sleep" internal drives the same as USB connected drives. Just not the boot drive.


    ----------

    Yep. Put them back in the anti-static bags they came in and pad the original cardboard box if not already. Then they're set for storage on a low shelf or seldom accessed drawer. I have a fireproof safe I keep gold bullion, cash, passports, and a few drives in. :)
     
  21. orph macrumors 6502a

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    #21
    THK Tesselator relay in depth can clear answers.

    good luck Korican100

    if it was me id look at a USB2/3 option, only problem is a lot of usb3 pci cards need power from somewhere which may move it to usb 2.
     
  22. omnious macrumors member

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    Mar 24, 2013
    #22
    This turned out way too confusing... :)

    Why not just use the HDD slot for what its meant to be - insert a drive in it and use it as a TM? :)

    Then, split the power from the ODD cage and route it into the main compartment. With that you can drive a number of fans, power USB3 cards, etc.
     
  23. ActionableMango macrumors 604

    ActionableMango

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    #23
    Yes, Omnious newbie speaks the truth.
     
  24. Korican100 thread starter macrumors 6502a

    Korican100

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    #24
    lol I totally know what you are saying here, and I get it. but:
    im already using odd power for 2 x SSD raid 0 setup + superdrive
    also, I want to have my backup external from my comp, for a few reasons (OCD reasons lol)
     

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