Is it possible to connect three servers to SCSI drives

[Gene Kornacki_3]

I have 2 Storageworks 2100's (mirrored and connected reduldant to 2 L's) and I want to be able to connect three or more machines to it. Is this possible with SCSI? Is there a multiplexer available? Anyone do this?

[Patrick Wallek]

I don't think I would want to try that. If you start connecting multiple machines, then you've got to make sure ALL SCSI IDs (including the IDs on the SCSI controller on ALL machines) are unique. I think this would get way too complicated.

[Bernhard Mueller]

Gene,

does the DS2100 have *four* SCSI ports? ie.
two controllers with two connectors each?
I have not seen that, but that does not mean anything...

however, I know that e.g. the SC10 JBODs as well as the DS2300 could have two LCCs (controller cards) each with two SCSI connectors. So if you run an SC10 or DS2300 in "full bus" mode every disk is seen on every port. Then you can attach up to four hosts (single attach).

However, as mentioned, you need to make sure each of your SCSI host bus adapters has a unique SCSI ID typically with the SC10 you would use 7, 6, 5, and 4 for the initiators while the disks had 0,1,2,3,8,9,10,11,12,13.

With the DS2300 the ID of the disk is bound to the slot# (14 slots!) so you may not use all slots then.

With DS2100 there is a switch (A-B-C) at the rear that determines the IDs of the four disks guess A was IDs 0-2-4-6. So you would have to find out which ones are free for the host bus adapters.

Regards,
Bernhard

[Bernhard Mueller]

One add'tl thing. The disks of the DS2100 can be used in the DS2300.

Regards,
Bernhard

[A. Clay Stephenson]

It's doable but each device (including the controllers must have a unique id.) Because of bus length limitations 3 hosts is near the practical maximum. In order to pull this off, you need a SCSI "V" cable which looks exactly like it sounds.

Two of your hosts (one set to 7) the other set to 6, sit at the ends of the bus with termination enabled. The middle host(s) with SCSI ID 5 (the next highest priority) is connected with the V cable and your array is connected to one end of the V and the other connection continues the bus to the host on the end. The middle devices (including the V connected host) must not have termination enabled. This is actually the way ServiceGuard was done on more than two hosts before Fibre came along and made it simple.

[Sanjay_6]

Hi Gene,

Normally we use the V cable to connect a shared SCSI storage to 2 servers in a two-node sg cluster

http://partsurfer.hp.com/cgi-bin/spi/main?sel_flg=partpic&pic_flg=part&stype=W&partnum=A5607A&HP_model=A5607A&model=&whichpic=%3F&template=main

Hope this helps.

regds

[Ron Lawson_1]

The answer really depends on whether you are asking if it is possible or if it is recommended and supported.

The DS2100 series was designed to support up to 2 hosts at a maximum data transfer rate of Ultra160. That is the maximum that is supported. Adding extra initiators might work, but you would be running the risk of hitting signal integrity issues in this non-supported configuration.