HP SmartArray 6404 RAID controller cache size?

[Heikki Siltala]

HP's SmartArray 6404 4-channel RAID card has 256 MB of cache. If I use
only one channel how much cache do I get for this one channel?

Answer 1: The technical guy from HP says that I get 256 MB.

Answer 2: HP's documents clearly state that 6404 is actually two
2-channel controllers sharing one PCI-X connector. This makes me think
that one controller has 128 MB of cache and so if I use only one channel
I get only 128 MB of cache.

http://docs.hp.com/en/J6369-90025/ch04s09.html

"The A9891A HP Smart Array 6404 comprises of two,
2-channel controllers sharing one PCI-X connector.
Each 2-channel controller has its own firmware and
is listed as a separate entry in the ioscan output."

And if I study the figures of the documentation I can see that both
controllers seem to have a large heatsink indicating that they have
their own processor. This makes me rather reluctant to believe that they
would have access to a shared 256 MB cache.

HP Smart Array 6400 Series Controller Support Guide
http://docs.hp.com/en/J6369-90025/J6369-90025.pdf

 

[Folkert Rienstra]

HP's SmartArray 6404 4-channel RAID card has 256 MB of cache. If I use
only one channel how much cache do I get for this one channel?

Answer 1: The technical guy from HP says that I get 256 MB.

And he is of course correct.

Answer 2: HP's documents clearly state that 6404 is actually two
2-channel controllers sharing one PCI-X connector. This makes me think
that one controller has 128 MB of cache and

so if I use only one channel I get only 128 MB of cache.

"256 MB (128 MB in the cache module and 64 MB on the (ie each) controller)"

So one question for you then:

Which channel gets the 128MB module?

Answer: none. The PowerPC processor on the board gets it.

http://docs.hp.com/en/J6369-90025/ch04s09.html

"The A9891A HP Smart Array 6404 comprises of two,
2-channel controllers sharing one PCI-X connector.
Each 2-channel controller has its own firmware and
is listed as a separate entry in the ioscan output."

And if I study the figures of the documentation I can see that both
controllers seem to have a large heatsink indicating that they have
their own processor.

So where is the SCSI chip on the expansion board then?

This makes me rather reluctant to believe that they
would have access to a shared 256 MB cache.

Because there is only one and it is the one without the heatsinks?

 

[Heikki Siltala]

Folkert Rienstra kirjoitti:

So one question for you then:
Which channel gets the 128MB module?
Answer: none. The PowerPC processor on the board gets it.

Yep, I assume you are right. There is only one battery-backed cache
module, so it must be available for all the channels.

 

[Folkert Rienstra]

Folkert Rienstra kirjoitti:

Yep, I assume you are right. There is only one battery-backed cache
module,

so it must be available for all the channels.

Available to the PowerPC processor and its firm-
ware which then decides what is used for what.