From the RAMCloud Wiki Home:
These goals are specified in terms of individual servers. However, we are essentially designing a cluster and should specify our goals in terms of the whole cluster.
That is, observing that
we should instead think in terms of total cluster storage capacity and total RAMcloud request throughput, rather than individual server capacity and throughput.
Revised goals:
We meet these goals by choosing appropriate hardware and replicating it as many times as necessary.
64GB / node? Not bad! $9501 for the privilege? Yikes...
$148.45/GB @ 64GB
$77.50/GB @ 32GB
Clearly, don't maximize GB/node. $/GB is somewhat more useful.
Question: Are there practical limits on the total number of nodes that have to be considered?
Power consumption: 143W-244W http://www.spec.org/power_ssj2008/results/res2008q1/power_ssj2008-20080212-00035.html
7.625W/GB (peak power, 32GB)
Similar to PowerEdge 1950
300W peak? 4.765W/GB @ 64GB
Power consumption of similar system (HP DL580G5): 271W-387W http://www.spec.org/power_ssj2008/results/res2007q4/power_ssj2008-20071207-00024.html
3.023W/GB (peak power, 128GB)
24GB / node. Not as good of density, but $57.71/GB.
Note, however, this node has more GB/GHz than the PE 1950.
24 / (2x1.86) = 6.45GB/GHz
32 / (4x1.86) = 4.30GB/GHz
Question: Will server load scale with memory capacity in practice? Asked another way, does increased memory capacity tend to result in the deployment of fewer servers?
Power consumption: 75W-117W? http://www.spec.org/power_ssj2008/results/res2008q1/power_ssj2008-20080311-00042.txt
4.875W/GB (peak power, 24GB)
$43.5/GB!
8/1.86 = 4.44GB/GHz
Not traditionally rack-mountable. More Ethernet ports/GB!
Power consumption: 50W-83W?? http://www.bit-tech.net/hardware/cases/2008/01/03/shuttle_sn68ptg5/9
Question: What impact does low GB/node have on networking infrastructure?
10.375W/GB (peak power, 8GB)! Worst yet.
Question: Can you find these in the wild? How much do they cost?
Is ECC necessary, sufficient, or neither? If we incorporate some other end-to-end data-integrity mechanism (i.e. store a CRC w/ data), is ECC redundant?
Sampled somewhat randomly from buy.com, newegg.com, ewiz.com, crucial.com.
Capacity |
Type |
Cost |
Cost/GB |
---|---|---|---|
2GB |
DDR2 UDIMM |
$17 |
$8.5/GB |
2GB |
DDR2 RDIMM |
$33 |
$16.5/GB |
2GB |
DDR2 FBDIMM |
$38 |
$19/GB |
2GB |
DDR3 UDIMM |
$29 |
$14.5/GB |
2GB |
DDR3 RDIMM |
$62 |
$31/GB |
- |
- |
- |
- |
4GB |
DDR2 RDIMM |
$50 |
$12.5/GB |
4GB |
DDR2 FBDIMM |
$72 |
$18/GB |
4GB |
DDR3 UDIMM |
$490 |
|
4GB |
DDR3 RDIMM |
$110 |
$27.5/GB |
- |
- |
- |
- |
8GB |
DDR2 RDIMM (Meta) |
$593 |
$74/GB |
8GB |
DDR2 FBDIMM |
$690 |
$86.25/GB |
8GB |
DDR3 RDIMM |
$1102 |
$137.75/GB |
Like most things life, the cheapest option is to hug the commodity curve (Unregistered DDR2 DIMMs).
I finally found an OEM board with 32 DIMM slots. It's a four-socket Opteron 8300 platform and uses DDR2 registered DIMMs.
The board runs $949 (http://www.8anet.com/merchant.ihtml?pid=6863&step=4).
Since it requires Opteron 8300 chips, the cheapest processor I could find for it is the 1.8 GHz Opteron 8346HE, which runs $389 (http://www.esaitech.com/commerce/catalog/product.jsp?product_id=51069).
4GB DDR2 R-DIMMs run about $65 (http://www.ewiz.com/detail.php?name=D2667R4G4H).
One problem is that this motherboard is inconveniently large, (13"x17") so I'm having trouble finding cases that will fit it. I'll assume we can find one for $500.
So 949 + 4 * 389 + 32 * 65 + 500 = $5085
$39.73/GB
Note that the memory itself runs $16.25/GB, so we're spending $23.48/GB in overhead.