MSA1000 Question

[NS_4]

If an MSA1000 has a single controller and a single san switch 2/8 and 7 servers all running windows 2000 and with single hba's in order to expand the fabric and add additional hosts (no redundancy) can only a second san switch 2/8 be added (with or without a isl cable to connect the two switches?) or is the second controller required as well?

[Uwe Zessin]

Neil,
you _can_ cascade another SANswitch 2/8 (with an ISL cable). I have put up a little ASCII drawing as an attachment, because the text area compresses multiple spaces.

You need to give that second switch a different domain:ID which can easily be done from the serial port.

What you cannot do is:
put a second controller into your MSA1000, connect another switch to it, put more servers on the second switch. The reason is because the MSA1000 controllers are in an active/standby role - one controller serves all (up to 32) LUNs and the other is in a waiting state to take over should the first one fail.

[NS_4]

Thanks for the quick reply!

I don't think my original question was 100% clear I couldn't be sure from the diagram if you are refering to the external HP StorageWorks SAN Switch 2/8-EL 322120-B21 ?

What I am wanting to know is if I have one MSA SAN Switch 2/8 (integrated) 288247-B21 internal to the MSA1000 with 7 servers with single HBA's (no redundancy) and i wish to expand the fabric and add additional hosts if I can add the second MSA SAN Switch 2/8 (integrated) and add more servers and if so do I need the redundant controller (because as you said they are active/passive) and do I need a cable to link them together or do they link together automatically using the port that is internal to the MSA1000??

[Uwe Zessin · Accepted solution]

I was indeed assuming that you had installed an external SANswitch.

Honestly, I doubt that it is supported what you want to do - the QuickSpecs explicitly mention that you can connect to another external switch _or_ to another embedded 8-port switch in another MSA1000.

There is no internal connection between the internal switches - they have a straight connection to the controller backplanes. I'm not sure if you aware, but you can also put a simple I/O module (for straight connection to an external switch) or a small hub instead of the embedded switch into that place.

You need the second controller if you want to provide redundant paths to you logical disks. 'passive' does not mean that the second controller does no work at all: it has an up-to-date copy of the active controller's cache and it responds to LUN inquiries. Makes sense, as the Secure Path software must know that there is an alternate way to the disks.

You just cannot do I/Os through the controller unless a failover has taken place - then they change their roles.

[NS_4]

Yep I have gone through the SAN Design guide and the MSA1000 documentation and they aren't very clear on this issue. It does say somewhere that if there are redundant controllers and two internal MSA SAN Switch 2/8 then there can be a mix of redundant i.e. hosts with 2 HBA's and SecurePath and non-redundant servers but the non-redundant servers will lose connection to the san (of course) if there is a fail-over, which is fine. However i'm only assuming that i can have 14 servers (each with a single HBA) connected to the two MSA SAN Switch 2/8 with the redundant controller for the MSA1000 installed, however I can't find anything that says I can do this.

[Uwe Zessin]

You can only have a mix of single- and dual-path servers as long as no Linux system is involved, because a booting Linux can cause a controller failover!

I am not sure I am understanding you correctly, but:
you cannot connect 7 single-path servers to one controller and another 7 single-path servers to the other controller (as I have already written: your servers cannot do I/O through the passive controller - the MSA1000 does not work like the VA71x0). Also, if I recall correctly, you are not allowed to put both controllers in the same fabric.

[Doug de Werd]

yes that is correct. You cannot put two of the MSA1000 internal switches on the same fabric. Basically the only time you would add a second internal switch to a single MSA1000 is to move to a redundant fabric - but your port count stays the same.

You can cascade the internal switch to another switch. If you need additional storage, you can add another MSA1000 and cascade the 2 internal switches together. If you don't need more storage, you can cascade to an external switch and connect the new server hosts to that, and they can then access the single MSA1000.

Thanks,
Doug

[NS_4]

Thanks guys, i've got it now!