Slashdot Mirror
3 Terabytes, 80 Watts
legoburner writes "The Enquirer is reporting that Capricorn have released a mini-itx based 1U-sized storage computer featuring four 750-GB hard drives and a 1-Ghz controller system with a typical power usage of an astounding 80 W per machine. A full 40U rack only uses 3.2 kW, which is less than 30 kW for an entire Petabyte!"
I dont think it's RAID anything at all.
The PetaBox TB120 says 120TB of space on 40 nodes. That's 3TB a node, and given 4 drives per node, that's 750GB drives.
So basically the RAID selection is left up as an exercise to the reader, they're just marketing raw diskspace with a very low power consumption.
Your hair look like poop, Bob! - Wanker.
I'll hope you mean in parallel on your drives. Peltier in series are not befitting that application unless you live in an unusually hot house, or have drives requiring cryo conditions.
Placing peltier patties in series decreases the amount of heat they can move, but obviously increases the temperature differential, but only if the stack is properly designed. It is very easy to put two peltier in series and have worse performance than a single device. In your case, with a non-static system (i.e. the hard drives are actively PRODUCING heat that you wish to remove) heat handling seems more imprtant than massive temperature differential. In thermodynamics, there is no free lunch... your secondary peltier is not only moving the heat away from the drive, but has to struggle with the heat it produces (however much electrical power it consumes is heat) as well as the first stage cooler.
To optimize a multistage thermoelectric cooler, a rule of thumb is that each stage should recieve 1/2 to 1/3 as much current as the previous one. This roughly translates to an equivalent voltage ratio, though as the temperature and temperature delta change, the silicon has different resistances, and the Seebeck also changes the apparent resistance.
In a PC, if you really want to do multistage peltier patties, and assuming they are 12v devices, you would notice an increase in performance (i.e. less heat coming off the hot side, and a colder cold side) if you were to connect the hard drive peltier to the +5V rail, and the heat sink peltier to the +12 rail. This is a very crude system, but definitely better than running both on +12.
I still maintain that the coolers in parallel are preferable for nearly any computer usage. You have a metric library of congress of BTUs (slashdot measurement) to move quickly. Stacked units do this poorly.
I have some data at home to determine near-optimal steady-state stacked configurations. Google is a help too, though sorting through the deep research and crackpot FAQs is rather tedious in this realm.
Rebuild rate for a RAID1, 2-drive, 750GB SATA set is around 75MB/s. (Raw read/write rates for 750GB drives are around 75MB/s as well.) So figure 3 hours to rebuild a RAID1 array.
Not sure what rebuild rates would be on a RAID5, probably about half of that? So 6 hours to rebuild the array?
(That's using 750GB SATA drives with Software RAID on a PCIe motherboard.)
Wolde you bothe eate your cake, and have your cake?