Dual DS2300's with Dual BCC's with Dual 4Si's?

[Alan Walters]

Hello,

I'm trying to take advantage of an H.P. year end discount/trade-in to replace my aging K360 with an RP5430.

The K360 currently has 2 A3312AZ Jamaica's, each of which are striped (Extent-based using LVM), then mirrored to each other (with Mirror/UX). Despite upgrading from dual HP-PB's to dual HSC's recently the I/O performance is still rather uninspiring.

The vendor configuring the RP5430 has suggested a single DS2300 with 4 18GB drives and splitting the channels so as to mirror 2 against 2. Their configuration only shows 1 controller and 1 BCC I'm worried about those single point of failure.

After doing a little reading and educating myself just enough to be dangerous, I'm wondering if configuring dual 4Si's to dual DS2300's (each with dual BCC's) and interleaving the 8 channels of the 4Si's to the eight ports of the BCC's wouldn't be much faster due to the primary/alternate paths while providing redundancy for any single 4Si/BCC/DS2300 failure?

In other words:
4Si #1 Channel A -> DS2300 #1 BCC #1 Port 1
4Si #1 Channel B -> DS2300 #2 BCC #1 Port 1
4Si #1 Channel C -> DS2300 #1 BCC #2 Port 1
4Si #1 Channel D -> DS2300 #2 BCC #2 Port 1

4Si #2 Channel A -> DS2300 #1 BCC #1 Port 2
4Si #2 Channel B -> DS2300 #2 BCC #1 Port 2
4Si #2 Channel C -> DS2300 #1 BCC #2 Port 2
4Si #2 Channel D -> DS2300 #2 BCC #2 Port 2

Is that feasible?

[Vincent Farrugia]

Hello,

Very interesting question, but unfortunately, you cannot do as you say.

Reason is... the 4Si card does NOT support a shared bus, NOR alternate links. You can connect a ds2300 with a 4Si, either with ONE BCC, or, if you want to use 2 BCCs, you have to configure it in split bus mode.

One 4Si would be enough for this job. I guess this is not pretty for you, so here is another alternative.

Configure exactly as you have said, but instead of using 2 4Sis, use 8 SCSI HBAs (or 4 dual-SCSI HBAs). This way, you can configure in full-bus mode, you can have alternate links. You WON'T have hardware RAID though. But you CAN have software RAID... mirroring using the excellent Mirror/UX. You mirror across ds2300s for maximum HA.

A little annotation... split-bus mode means that each controller controls 7 harddisks (split). Full-bus mode means that each controller controls ALL harddisks (making way for alternate paths).

Any more questions just post.

HTH,
Vince

[Alan Walters]

Thanks for the info and suggestion.

The RP5430 only has 5 usable I/O Slots, so I'm not sure I could get away with filling 4 of them.

If I wanted to compromise and settle for using only 1 DS2300 but still have Mirroring, could I use 1 4Si with 2 BCC's in Split-Bus configuration? Recognizing the single point of failure potential at the 4Si and the absence of Alternate Paths? I'm only planning on having 4-6 spindles (2-3 Mirrored) in the DS2300 so the need for Alternate Paths might be lessened?

In other words:
4Si Channel A -> DS2300 BCC #1 Port 1
4Si Channel B -> DS2300 BCC #1 Port 2
4Si Channel C -> DS2300 BCC #2 Port 1
4Si Channel D -> DS2300 BCC #2 Port 2

[Vincent Farrugia]

Hello,

Yes, you can connect 1 ds2300 in split-bus mode connecting to 2 BCCs, but you cannot do it the way you pictured it.

Remember that the 4Si does NOT allow connections to a shared bus. You have to connect to only 1 port of the BCCs, leaving the others terminated. That's the way it is, unfortunately.

Well if connecting 4 cards ia a hassle, you can have 2 dual-port cards instead, A5150A is a good example. If you also need LAN, there are combo cards with 2 SCSI LVD and 2 10/100 network ports.

HTH,
Vince

[ooi]

Dear Vincent,

Very glad to see your reply. I am looking for the same answer too. But according to the 4Si documentation, HP does not support multi initiator. I suppose we cannot connect more than a channel to a JBOD. Even it works, but HP is not going to support. Can I have the confirmation from you?

Is DS2300 must be configured in split bus to be able to use with 4Si? How do I connect if I use share bus with 4Si? Or the answer is no?

I currently configured a DS2300, split bus and connected channel A & B to the split bus of DS2300 (2 disks at each bus). Configure as RAID 5. Not sure if this is a supported model? This is a single point of failure design. What if I use raid 10 instead of raid 5, is this a supported design as well. This will eliminate the SPOF.

Appreciate your feedback.

Thanks.

[Vincent Farrugia]

Hello,

Actually you can get the answr from my first answer in this thread. The things you said are all correct.

Indeed, 4Si card does not support multi-initiator. ds2300 MUSt be configured in split-bus mode, as you said. You CANNOT chare a bus with the 4Si.

Your configuration is the best you can do with a 4si, it's correct and sound. You can do whatever RAID level you like...

Reason is... the 4si card actually is NOT a high-availibility card... it does NOT support MC Service-Guard with it. You cannot remove SPOFs with this card. All 4 channels in this card are separate RAID controllers, so you cannot have multiple channels to the same controllers. All you can do is to attach one channel to a controller governing a number of disks, and do RAID on them. That's it... no high-availibility involved whatsoever (except, of course, having the RAID protection in the event of a disk failure). So you can do any RAID you want depending on your needs of course.

If you want high-availibility, you can do the setup I suggested in my previous answer.

HTH,
Vince

[ooi]

Dear Vincent,

Many thanks to you. I got all my doubts cleared.

regards,
Ooi

[Alan Walters]

Hi Vincent,

Thanks for the feedback so far. Can I bother you some more? Earlier you had suggested using 8 HBA's or possibly 4 dual-channel (such as the A5150A).

I've recently discovered the A6829A which is Ultra160 dual-channel. If I read your previous example correctly and the A6829A supports connections to a shared bus (how can I tell?) then I should be able to configure quad A6829A with dual DS2300 each with dual BCC's and still have full bus mode and alternate links:

A6829A #1 Channel A -> DS2300 #1 BCC #1 Port 1
A6829A #1 Channel B -> DS2300 #2 BCC #1 Port 1
A6829A #2 Channel A -> DS2300 #1 BCC #2 Port 1
A6829A #2 Channel B -> DS2300 #2 BCC #2 Port 1
A6829A #3 Channel A -> DS2300 #1 BCC #1 Port 2
A6829A #3 Channel B -> DS2300 #2 BCC #1 Port 2
A6829A #4 Channel A -> DS2300 #1 BCC #2 Port 2
A6829A #4 Channel B -> DS2300 #2 BCC #2 Port 2
Mirror/UX across the dual DS2300's

I'm working with a VAR to put this system together, but frankly I don't trust his fancy configurator program. For starters it shows the rp5430 as having 6 usable PCI Slots when all the docs I've read show only 5 - the 6th is in the Core I/O and therefore unavailable for use with the DS2300's?

Also according to what I've read, only 2 of the PCI slots are Ultra160 capable, so only 2 of the 4 A6829A will be running at full speed. Will I be wasting the capability of the A6829A if I have half running faster? Will it negatively affect the alternate pathing? Should I just quit being cheap and get the rp5470 with 10 PCI slots?

TIA

[Vincent Farrugia · Accepted solution]

Hello,

I did some research, and some common sense lacking from my part :-)

If you do your configuration, you will have 3 alternate paths, not 1 :-) One alternate path is enough. Actually, I don't know whether the server would support a number of HBAs that high (8).

You can connect as shown in the attachment. Read the note shown there as well (taken from the ds2300 User's Guide).

That way, you connect only 2 cards in your server (dual), so it will be ok for your 5-PCI-slot rp5430.

Also, you can have only 13 disks (not 14), since SCSI-3 serves 15 peripherals (13 disks + 2 HBAs).

Hope this attachment works...

HTH,
Vince

[Alan Walters]

Excellent diagram!

I'm emailing that to my VAR right now to help in the configuration. Can you provide me the link to that DS2300 User's Guide? I searched ITRC for 'DS2300 User Guide' and came up short.

However I did find the following which is causing me some concern:
According to this Doc dated 07/02 the A6829A is not (yet?) supported:
http://www2.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000062104163

According to this Doc also dated 07/02 multi-initiator Ultra160 HBAs are not (yet?) supported on initial release of the DS2300 due to a hardware compatibility issue:
http://www2.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000062108688

Am I incorrect in thinking the previous Diagram utilizes Multi-Initiator HBA's?