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28479
June 23rd, 2013 16:00
Dell SAS and FC storage
Hi,
MD3000 tech spec states:
SAS connectors (per storage controller): 2x4 3.0 Gbps SAS (SFF 8470) "IN" connector for connection to the host.
If we use 5/E SAS HBA maximum throughput we could get is 3 Gbps?
and MD3000 could support max 6 Gbps to server with 6 Gbps HBA adapter?
If replacing MD3000 with DELL FC storage that includes four on board 8 Gb/s Fibber Channel ports we will benefit in throughput even by connecting storage with one port 4 Gbps HBA PCIe 2 Gen adapter (+1gbps)?
Max throughput could be 32 Gbps (four on board 8 Gb/s Fibber Channel ports) but as our Dell server has two PCIe x8 and two PCI x4 slots we could expect max 24 gbps throughput from FC HBA?
Is it correct? This is just throughput in general but lets say disk drives on both storage are the same - SAS 300gb 15K.
Thanks
Dev Mgr
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June 23rd, 2013 21:00
The MD3000 SAS unit has 2 4-channel 3Gbit/s ports. This means that each port can yield up to 12Gbit/s in bandwidth. Between the 2 ports and 2 controllers that is up to 48Gbit/s in bandwidth (though due to its active/passive design you can only get up to 24Gbit/s to a single LUN/virtual disk).
6Gbit adapters (not supported, but may work) wouldn't make things any faster on an MD3000.
On the other hand, the newer MD3200 (SAS) is a 6Gbit/s model and has 4 4-channel 6Gbit ports on each controller. This yields up to 2 x 4 x 4 x 6 = 192Gbit/s in theoretical bandwidth (96Gbit/s to each controller, and therefor to any given single virtual disk).
The MD3600F (only Dell Powervault SAN with FC controllers (Dell offered EMC and offers Compellent, but those are very different price ranges)) has 4 8Gbit FC ports per controller. This yields up to 64Gbit/s in theoretical bandwidth (32Gbit/s to a single controller again).
Note that these are theoretical bandwidth limits. Unless you're using SSDs, it'll be pretty much impossible to get anywhere near this type of throughput (even the MD3000's 24Gbit/s), even with raid 0.
dellUser95
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June 24th, 2013 01:00
And about server side:
How much theoretical bandwidth we could get with 5/E that has max 3 Gbit/s. Is it correct that on 8 lane PCIe x8 we will get - 8 x 3 = 24 Gbit/s? or 48 (24x2) as 5/E has 2 ports?
And with FC 8 Gbit single port HBA adapter with same PCIe x8 it will be 64 (8x8) Gbit/s theoretical bandwidth?
Thank you,
Dev Mgr
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June 25th, 2013 10:00
Bandwidth will be limited by the slowest common denominator, so using an 6Gbit HBA to a 3Gbit SAN means you get 3Gbit speeds.
Each port has its own 4 channels that each is 3Gbit or 6Gbit (depending on the hba).
awer1
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June 25th, 2013 13:00
5/E is only 3Gbit HBA so does it mean that are limited to only 3Gbit even if we use on PCIe x8 or PCIe 4x slot?
thanks
Dev Mgr
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June 26th, 2013 09:00
The SAS5E has 2 3Gbit quad-channel ports, so each port can yield up to 12Gbit/s in bandwidth, or 24Gbit/s combined.
This has to go through the PCIe slot obviously, and therefor the PCIe bandwidth plays a role too. A PCIe 4x slot on PCIe version 1.0 yields a lot less bandwidth than an 8x slot on PCIe version 2.0.
Some info on PCIe bandwidth can be found on Wikipedia (en.wikipedia.org/.../PCI_Express).