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Re: [ProgSoc] iSCSI - the new I in RAID?



On 23/08/2007, at 9:10 PM, jedd wrote:
 Andi - I evaluated some HDS gear in a previous life, prolly around
 2001, and was impressed with it right up until I saw the price.

 Have you worked out what your cost per GB is on that kit, including
 the port costs on the switches?   Did you do any comparative tests
 for throughput?  It seems to me that you should be able to build up,
 from relatively commodity hardware, an iSCSI network that out-
 performs a SAN, simply because at the same price you can out-trunk
FC (or you can match it at a cheaper price). Actual benchmark results
 for this kind of research are pretty thin on the ground, though.
Actually I need to revise my cost upwards. I was looking at an older  
quote from when we were looking at 4TB instead of 8.
Cost is $26- per GB.
Cost is $6700- per FC port (currently using 10 of 32)

These costs include the cost of the SAN, 2x 16port McData FC 4Gbps switches and 5x dual port 4Gbps Qlogic FC cards for the servers.
The problem for us Jedd is that our file and DB servers have a rather  
high load of random read/write. We're serving up a fair volume of  
data through branded sites or web services to news.com.au/HSBC/ING/ 
NAB/CommSec/Lonsdale/vanEyk, etc - the problem is that most of this  
are ~1Mb PDF reports (clients generate a PDF report of dynamic data  
which is stored and then uploaded to the client) and we found the  
level of latency with simultaneous iSCSI read/writes when we did  
testing in the lab to be unacceptable. Let me rephrase that. It would  
have been fine for 1-2 years of systems data growth but not for 5.
This SAN doesn't even crack a sweat because it's so over-specced for  
what we need. (The pointy-haired boss wants a 5 year life cycle hence  
the ridiculous capacity). We're currently on 9% capacity because we  
tend to double our data storage needs every 18months. Despite that  
fact that it'd be cheaper, they wanted the full required capacity for  
the 5 years now to 'avoid' an upgrade of capacity later [when of  
course it'd be cheaper] *sigh*)
Now what you say about ISCSI outperforming FC, it is possible  
depending on your setup, but keep in mind that most base level  
systems are still 2Gbps at heart. This SAN is fully 4gbps based FC  
(compared to 1gbps ISCSI). Combined with the number of drive spindles  
we have, the speed of the drives (I wish I could get 15K SATA  
drives!) but most especially for our needs -cache, cache and more  
cache and bus speed, FC blows ISCSI out of the water for us. For us  
the requirements are speed followed by capacity, I wish it was the  
reverse.
-Andi

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