Hi Ed,
Thanks for the response. Below are the details which explains the scenario better.
The system can be considered as one with dual CPU complex, but a single SSD. There are 2 operating systems, OS-1 and OS-2 running on each of the CPU complex, OS-1 boots first and takes control of the SSD and starts the target. OS-2 which boots up later uses initiator to connect to target over an interface connecting the 2 CPU complex. There is no switch in between, its a back to back Ethernet network over which AoE is being used by OS-2 for all disk accesses.
Now, at some point in time, OS-1 has to be shut down, which means target is not available anymore. OS-2 will now start the target on loopback interface using "vbladed 0 0 lo /dev/sda". As this system is going to run for a long time, i want to understand the overhead that is there in disk access from the POV of applications running on OS-2. I want to compare the AoE based access mechanism in the above scenario with the case where OS-2 applications are directly accessing the SSD.
Now, all the queries below are for this case where OS-2 has the initiator which tries to connect to the target which is also running in OS-2, no network in between. Not sure if your previous responses would still be valid for this specific case as for example MTU might not be a consideration from the actual data transfer POV.
a. Wanted to understand if the AoE model has specific optimizations done to make this as close as possible to a regular local disk access.b. I see the Linux storage stack @ https://upload.wikimedia.org/wikipedia/commons/3/30/IO_ , I was wondering about the overhead involved in accessing storage from application POV once I restart the AoE target locally.stack_of_the_Linux_kernel.svg i. Overhead from the perspective of additional LOC involved as compared to a local disk access ii. Overhead from the perspective of throughput possible as compared to a local disk access c. Do you think further optimizations are theoretically possible to take care of this specific scenario to make it just like a regular local disk access?
Thankyou,
nivin
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