scsi-target and the buffer cache

[Eric Anderson]

I'm curious about whether a target mode device would use the buffer 
cache or not.  Here's a scenario:

Host A: has fibre channel host adapter, in target mode, large memory 
pool, and another fiber channel host adapter connecting to fibre channel 
block device.
Host B: Fibre channel host adapter, connecting to Host A.  'sees' the 
target mode block device created by Host A.

Will Host A use the buffer cache to cache blocks between the real block 
device, and the shared target mode device? 

What about if Host A put a filesystem on the block device, created a 
single file the size of the filesystem, and shared that filesystem via a 
target mode device to Host B? 

What I'm wanting is a box (FreeBSD?) that can be placed between a fibre 
channel block device (like a RAID array), and a fibre channel host using 
that block device, and act as a block cache for that device, using the 
FreeBSD's memory.  If it had a significant amount of memory, this could 
be very useful. 

Eric


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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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