XP12000 - Direct Connect or SAN Attach?

[Alzhy]

Our use of a SAN merely centers on the ability to have more server connections (which is a non-issue) and "move" disks around (presenting LUNS to servers on the fly - which can be done "in-array" by LUN-multipathing or presenting LUNS to more than one CHIP port - in effect to more than one server).

I am aware of the significant difference in cost between switch ports and CHIP ports but notwithstanding:

1. Is there any other advantage to using a SAN than directly attaching (1 Array port per Server HBA). We're not using any SAN based backup.. out Tape Infra will be on a different SAN and uses the backup server's bus in moving data from disk to tapes.

2. Our environments are VERY I/O intensive - will a direct attach to the XP have considerable advantage over a SAN connection? Will a direct attachment to an XP be loop (AL) or Point to Point?

[Steven Clementi]

Is Direct Attachment even supported on the XP line? I know it is not suported on the MSA and the EVA, but am unfamiliar with the XP.

I would think that, if support is not an issues, directly attaching your hosts to your storage would have some performance increase over using a switch, but not so much difference that it would be worthwhile to use the storage directly attached.

Obviously, Direct attachment might make sense if you only have 1 or 2 servers (Which is IBM's stance as the DS4000 line allows 1 to 4 direct attached hosts depending on the model).


Steven

[Alzhy]

Steven,

The XP line is basically a Hitachi array as you probably know already. We've an old HDS9960/XP512 (but still superbly working) that is simply direct attached - FC-AL - to each server. Am not sure though if an XP once connected to a fabric is essentially a loop (AL) connection.

What we do as far as split mirror backups is concerned is that the LUNS that will be the split mirror LUNs are presented to more than one server - so we can move the VxVM diskgroup around. Simply split off the VxVM diskgroup and deport from prod server and import it on to the server that needs it.. ie. a backup server or DSS/Test server - all done without a SAN. That's the beauty of this feature multi-pathing feature of XP/HDS arrays.