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Thread: For the sake of an argument: 500w enough for 38 HDDs? 1KW for 76 HDD's?

  1. #11
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    You will need staggered startup of some kind.

    The normal operation draw is no problem at all, but the startup is, when executed by all drives simultaneously.

  2. #12
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    38 drives x 3A = 114 amps and that is only for the hard disks to spin up from a cold boot.

    I don't even think he can get the whole system stable (psu not crapping out) even if he started each SATA (37 drives) one at a time after a cold boot with the C drive.

  3. #13
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    Well, it won't be much more than an Amp per drive after startup, so let's say 40 apms on 12 V. Some PSUs do that easily.

    But it can be troublesome. For example, the startup draw even without spinning up can e.g. kill the 5 V.

    I'd say put them in stacks of external enclosures 4 or 5 drives each.

  4. #14
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    Quote Originally Posted by uOpt View Post
    Well, it won't be much more than an Amp per drive after startup, so let's say 40 apms on 12 V. Some PSUs do that easily.

    But it can be troublesome. For example, the startup draw even without spinning up can e.g. kill the 5 V.

    I'd say put them in stacks of external enclosures 4 or 5 drives each.
    But even if it is only 1 amp in use..that is 38 amps just for drives...you do need to run other 12v devices

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    i don't think that 7200rpm HD use 3A to boot...

    ...i have 6 HD, 5x 7200rpm & 1x 5400rpm...that was powered by an enermax noiseteker I 600W with two +12v lines with 18A each and the psu powered also a Pentium D920@4500 1.60v and a X1900XTX...

    ...if the HD use 3A to boot only the 6x HD that i have will use 18A and the enermax for sure fail (also because the s-ata in this psu are on the same line where's the cpu)...

    ...now i have 8x HD (6x HD + 2x Raptor 74gb) but i use a Corsair HX620W whit the same config and also that psu never fail to power my pc...

    ...btw for 38 HD i will go for at least a very good 1KW/1,2KW psu...

    ...bye

    p.s.: sorry for the "english"

  6. #16
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    Quote Originally Posted by Iantikas View Post
    i don't think that 7200rpm HD use 3A to boot...
    I have a Fluke ammeter that proves otherwise.

    Also, you can see that the hard drive manufacturer's website also specifies a spin-up load of 2.5 to 3A (depending on the manufacturer.)

    I actually had to "prove" this because Seagate was claiming that a certain hard drive enclosure was "incompatible" with their hard drives because their hard drives need 3A to spin up and the power pack included with the hard drive only puts out 2.5A.

    I confirmed that the hard drive did in fact draw 3A on a cold boot, but the power pack put it out without issue with the +12V dropping only .02V under this excessive load. The 3A draw lasted about 2 seconds before coming down to 2A. This is why staggered spin-up works so well.

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    i have experienced several instances of adding a fourth HDD to find on spin up there is click-click-click. replacing the psu with a new powerful one and no more probs. its true they use a lot of power on spinup.

    but managing 38 drives? excluding the power requirements which have already been dealt with above, i would certainly want an enterprise level enclosure with good management utility including smart status and preferably leds indicating drive status, working/fail. not only for the blinky lights which would be awesome but that would be kinda a lot of data to lose so i would want to be sure i was replacing the right failed drive.

    i would also go for the enterprise sata drives of which wd and i believe also seagate offer and not the consumer ones.

    in the end though when so much data is concerned (assuming these will be 500gb drives) backing it up daily is going to be a problem unless there will be some enterprise level very expensive backup solution or a duplicate array.

    so he should really think is all this data necessary to be on a "working" array. it should really be split up into a smaller "working" array that is used for current data and backed up daily and then another array which is archive material and already backed up and the backup archived.

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    Hmmm... why wouldn't you just buy a NAS enclosure and be done with it? Or for that matter 2 NAS enclosure for the amount of drives he's looking at. Although to be honest the whole thing seems like an exercise in futility. How much would you spend on enclosures to hold the drives, power supplies to feed the drives, RAID cards to string them together, and OS that can handle all that storage? You'd probably come out better just buying an "out of the box" solution. Not trying to be too negative, I'm all about frankinstining left over hardware but I don’t' think you would come out on top in this situation.

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    I dunno y he would spend that much money on nas enclosures for 38 drives if he thinks he can get away with a 500watt psu. The cost of a good psu is miniscule to that of your suggestion. Even the cost of 38 external enclosures would outweigh the cost of a 1300watt powersupply assuming he already has the hardware/software for it already.

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