Smart Arrray 6404 / MSA20 - span disk shelves?

[Frank Andrews]

I have a client who has purchased a new Smart Array 6404 with 512Mb Cache upgrade and they have 2 x MSA20 disk shelves. All the hardware has the latest firmware applied. They are running Windows 2003 Server and have the most recent downloadable drivers and ACU installed.

They would like to be able to be able to use both shelves to create a RAID10 set. The issue is that when I browse the ACU I can see the two MSA20's as seperate arrays and don't appear to be able to use them together for one Array. I know the 6404 is able to span shelves, from the following link (question 4)

http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/smartarray6400/questionsanswers.html#tc4

It seems to me that even though the 6404 can span shelves, it can't do this with MSA20's as they have their own controllers on board? Perhaps the 6404 can only span disk shelves when "dumb" SCSI shelves are attached? Am I correct?

[Víctor Cespón]

There's something I don't get:

- I can see the two MSA20's as seperate arrays

If it's a new installation and you have not configured the controller, you should see only disks hanging from the SmartArray 6400.
If there's a "Parallell SCSI Array A" then an RAID has been already created.
The controller on the MSA20 is there for translating from SATA to SCSI and provide caché, but the MSA20 must be connected to a SmartArray or MSA1500 to configure RAIDs on it.

[Uwe Zessin · Accepted solution]

> It seems to me that even though the 6404 can span shelves,
> it can't do this with MSA20's

Right. The 6404 just acts as a pass-through for the MSA20-embedded SmartArray controller's logical disks.

The situation is different, when the MSA20 is connected to an MSA1500cs or MSA1510i. In that case, the MSA20 encapsulates each physical disk drive into a single-disk "RAID-0" and lets the external controller do the RAID function.

[Frank Andrews]

Thanks Uwe, this is as I suspected. If money wasn't the problem, what hardware could the client use to utilise their SATA disks in a RAID10 over two shelves?

Or would they have to abandon the SATA disks and buy SCSI disk shelves/disks for this purpose?

[Uwe Zessin]

They would have to put an MSA1500cs or MSA1510i (a Fibre Channel or an iSCSI storage controller) between the servers and the MSA20.

I have been following the discussion about these combinations for some time now and it seems that they don't seem to work well together. The MSA20 is a constant trouble maker.

I guess the user wants to use RAID-10 for performance? In that case, the SATA disks are not the right selection anyway and he should replace them with SCSI disks.

[Frank Andrews]

If money (or the customer's disapointment!) wasn't an issue, what hardware could they use? They wouldn't want an MSA1500 series device, but which SCSI disk shelves are available to direct connect to the S6404 for RAID10 across shelves functionality?

[Uwe Zessin]

The SA6440 supports two current enclosures:

- the MSA30 SB - 14 universal disk drives on a single SCSI bus

- the MSA30 DB - 14 universal disk drives, distributed on two SCSI busses. (The first 7 disk drives go one the first bus, the remaining 7 disk drives on the second bus)

[Frank Andrews]

They have a smart 6404 controller which has the four external VHDCI SCSI ports, is this compatible with the disk enclosures you mentioned?

[Uwe Zessin]

Yes, however, they need to understand, that an SA6404 is really _two_ SmartArray controllers:
- one on the PCI-board
- the second on the expansion module

It is not possible to span disk drive arrays across all 4 ports. So they might get along, for example, with two MSA30 DB to use all 4 busses and have some separation.

[Frank Andrews]

My understanding was that a 'span' can be done on Port1&2 or Port3&4. Its not clear in the FAQ if the controller allows 1&2 to be spanned at the same time as 3&4, it seems to imply that its 1&2 or 3&4, but doesn't explain if four shelves can be used in two spans simultaneously.

http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/smartarray6400/questionsanswers.html#tc4

"Q4. What is the maximum number of channels that can be spanned by a single RAID volume with the Smart Array 6400 Controller?
A4. A RAID volume can be configured across a maximum of two channels on the Smart Array 6400. RAID volumes on the SA-6402 are able to span channels 1 and 2. RAID volumes on the SA-6404 are able to span channels 1 and 2 or channels 3 and 4. "