High availability email server...

[Andrew Laurence]

At 11:49 PM +0200 7/28/06, Pascal Gienger wrote:
>In the Apple case we need to distinguish Apple XSAN Harddisk chassis 
>and the XSAN software. The XSAN software seem to give you a special 
>filesystem for SAN issues (at least I read this on their webpage).

Let me dissect this a bit.

The Xserve RAID is Apple's RAID appliance box, two 
non-redundant/failover 7-disk controllers in one box (14 disks 
total), each with FC connectors connecting to (whatever).  The 
administrative application is a Java app.  No Mac OS necessary, no 
special Apple goo.  A group here is using it as raw storage for 
VMWare (VMFS).

Xsan is Apple's licensed implementation of ADIC's StorNext file 
system.  It's its own file system, *NOT* HFS+.  StorNext requires a 
dedicated, private Ethernet network for communicating metadata 
information between the nodes and controllers.  This topology is 
where it falls down with lots of little files -- lots of little files 
means more metadata flying between the nodes and controllers; it's 
inherent to the StorNext design.  On the flip side, Apple's Xsan 
product is a very cheap way to implement a StorNext controller; 
Apple's client licenses are (relatively) cheap as well, but ADIC will 
happily sell clients for Linux/AIX/Solarix/other that all work with 
Xsan.

-- 
Andrew Laurence
atlauren at uci.edu