Hugh and myself made some rather surprising discoveries this week, about the performance of a networked XServe RAID connecting multiple Macs using a fibre channel switch:

STILL TO BE CONFIRMED --- BUT

we configured one channel ( one half of xserve raid ) - to drive 3 catalysts.
the one half was set up as 3 separate 2 drive raids.

3 catalyst systems running on dual g5's were then connected to the xserve raid via the Qlogic 5200 fibre switch - everything was connected to a fibre channel switch.

each raid volume called 'Raid 1', 'Raid 2', 'Raid 3' mounted on all the macs! through the switch - without any configuration!
meaning volumes are totally shareable - WITHOUT any extra configuration of anything.
XSAN was not required.

We started off by playing back 4 layers on each catalyst - all worked fine.

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i think we might be able to drive up to 6 ( or even 8 ) catalyst media servers - each with 4- 6 layers from a single xserve raid.

Ultimate performance will depend on the data saturation characteristics of the fibre channel switch, and the end user content requirements.

we have not finished testing yet.
im still not yet sure whether this will work so well with long clips, which cannot be completely loaded in the cache.

the key to this is to divide the xserve raid up into smaller drive sets- 2 or 3 drives /raid set.
as reagan initially reported the performance at standard definition is not better with 7 drives than with 2 - a 7 drive raid set can playback 7-8 layers - but so can a 2 volume raid set.

this is because playing back 6-7-8 layers the bottleneck problem becomes a processor limitation.


So dividing up 14 drives in the biggest xserve raid will give you 3 raid sets/channel, each with 2 or 3 drives.

Each Catalyst mac media server runs from its own RAID set - so the data access for each server does not collide across raid volumes.
But all volumes are readable on all macs networked through the fibre channel card.

The fibre channel system means that you have actually directly networked all your volumes together.

This has an enormous potential to help in the content management of large shows, as any mac connected to the fibre channel switch can see all RAID volumes.