HP P2000 G3 Directed Connected

[Alysson]

On the HP P2000 G3 dual controlled with 8 Gb FC Ports, could 4 hosts be directed connected on each port of the storage?

Thanks.

[Torsten.]

IMHO in theory yes, but I prefer to have redundant paths.

[Alysson]

Yes that's what I think so, but I need to be 100% sure before make this investment.

I know that redudant switchs it's a robust and ideal solution, however for costs reasons we need to get a entry-level storage solution with directed attached option for later be able to foward to a switched solution.

[Torsten.]

You have so many SPOFs then:

The servers HBA and each of the P2k controllers.

If a single item fails you cannot work.

You may consider to buy smaller FC switches or even use the iSCSI option of the array.

[Alysson]

I know that running this way there will be a lot of  SPOFs. However, this will be a initial implementation for later add switches and get redundancy for the solution.

The storage with both  FC/iSCSI option costs 35% higher. My intention is get a inital storage solution that later will be possible, when there will be more budget, upgrade for a robust solution.

[Alysson]

Has anyone experienced direct connecting 4 servers?

[Johan Guldmyr]

"On the HP P2000 G3 dual controlled with 8 Gb FC Ports, could 4 hosts be directed connected on each port of the storage?"

Could you define a little better? How would you connect 4 ports on each port of the storage? This would IMO require a SAN-switch. Or do you mean one host to one port on the storage? (there are two ports in each controller).

The last idea will work.
The storage ports are even in Direct Connect mode by default.

I don't remember if I've seen four DC, but I have seen a mix of DC and SAN-switch to the same P2000 G3.

[Torsten.]

This will work, but if a storage controller fails 2 servers will be disconnected.

Even a single 8 port switch would be a better solution for the beginning.

An alternative would be a small EVA4400 with embedded switches, but likely more expensive.

[Johan Guldmyr]

Yeah, it's not like an 8Gbps switch is needed for this setup, the ports on the P2000 would work fine in 4Gbps and I doubt you'd get speeds from one server going above 4Gbps anyway.
For example the 4/8 switch A7984A (looked at one page on the Internet and it was priced at 755 American $).

[Alysson]

Thanks guys for the information, that's what I needed to know for now.

But Johan, Why did you say that I'd probably not get speeds from one server going above 4Gbps?

[Johan Guldmyr]

Well, is it normal to get more than 400MB/s (or whatever 4Gbps amounts to) from one disk shelf?

Probably with the SFF shelf (so max is 24 disks on one shelf).

But if you're doing this kind of on the cheap I presume you'll use 7200 RPM SAS/SATA disks?

[Alysson]

I see. I plan to use a mix of SAS (15k) and SATA (7.2k) disks.

[Alysson]

We just bought the P2000 G3 and I got another question:

In a implementation with one host directed connected to controller A and another host directed connected to controller B, could a volume owned by controller A be accessed by a host that's connected to controller B?

Thanks in advance.

[Alysson]

Just to clarify , in the question above I meant a case in normal operation, without controller failure.

[Torsten.]

Let's assume you have 2 servers, the array has 4 FC ports.

You should connect
server A to ports A1, B1:
server B to ports A2, B2

for redundancy.

You can now create 2 vdisks with volumes, one for server A, another for B, each owned by one controller, if you like.

[Alysson]

Actually, I know that's not the best solution and later we'll get a switch to improve the implementation, but I plan to direct connect a third host to the storage and in this case I won't be able to connect servers A and B to both controllers.

I am almost convinced that during a normal operation a host directed connected to a controller won't be able to access the volume owned by the other controller, but I need to be 100% sure on this.


Thanks.

[Torsten.]

You can always change the preferred owner of a vdisk.
You should access the volumes via the preferred owner for performance reasons.

[Alysson]

But can a host access a volume via the non preferred owner?

[Torsten.]

Let's assume a real SAN:

The preferred owner fails or the SAN connected to the preferred owner fails, the other controller becomes the current owner and owns the disk.

While doing the presentation you present a volumes via the array ports. Usually to all 4 array ports.

But the access via the "non-owner" will not be optimal (slower).

[Alysson]

OK. Thanks for that.