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SCSI redundancy provided by SCSI duplex configuration ?

 
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Jdamian
Respected Contributor

SCSI redundancy provided by SCSI duplex configuration ?

Hi

I noticed that rp3440 and rp4440 servers (and some integrity servers) are configured as simplex (both internal disks use the same SCSI channel) by default. Therefore, there is no SCSI redundancy for internal disks.

If server is updated to SCSI duplex... is the SCSI redundancy granted ?

Some HP contact told me that the SCSI duplex mode doesn't provide the SCSI redundancy... I was shocked ! I cannot believe HP to sell servers without internal SCSI redundancy...

Would you confirm or deny this issue?


Thanx in advance
4 REPLIES 4
Phil uk
Honored Contributor
Solution

Re: SCSI redundancy provided by SCSI duplex configuration ?

RP4440:
This has a PCI SCSI bd in slot 1 (part of the core IO) which consists of two controllers.
By default the machines come with Both of the internal disks on only 1 of these 2 controllers (Simplex) - this allows you to use External scsi port B for external storage etc.
If you configure the machine for Duplex, the disks are indeed then on seperate controllers for redundancy - albeit the controllers are on the same PCI card - which is then a SPOF.

RP3440:
The lower and middle disks are on one controller, and the upper slot is on a seperate controller. This upper slot shares the same bus as the external SCSI port, so you have to be careful with any external device addressing, and avoid having a tape array for example on the same bus as the upper disk.
Hope this makes sense.
Phil
Phil uk
Honored Contributor

Re: SCSI redundancy provided by SCSI duplex configuration ?

Also, don't forget, these machines are only "entry level", and dont have the sophistication (and cost ££££) of those machines with greater resiliance built in.
Phil
Torsten.
Acclaimed Contributor

Re: SCSI redundancy provided by SCSI duplex configuration ?

As phil mentioned, this are entry class servers.
The rp4440 can have a duplex config too. In this case you use both channels on the core I/O card for the internal disks.
Let's compare this to almost all RAID controllers in servers: the controller card is the SPOF unless you mirror across several controller cards.
To work around this, you may connect external disks (e.g. DS2120) to another controller and mirror each internal disk to an external disk, if you want.

Hope this helps!
Regards
Torsten.

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Re: SCSI redundancy provided by SCSI duplex configuration ?

Hi Oscar,

SCSI duplex on rp3440 / rp4440 requires a hardware component.

Yes it becomes fully scsi redundant because it can be wired to two different controllers physically on the mainboard and then mirrored.