With any SAN, consideration for the balance between performance and capacity always must be paramount. If too much emphasis is placed on capacity, performance will surely suffer, so heed the word of your storage vendor about storage layout. In this chapter, we focus only on how to increase storage with a simple storage layout, and not on performance.
We use the following two servers to illustrate our concepts.
The particulars on Machine 1 are as follows:
[root@cyclops root]# uname -a Linux cyclops 2.4.9-e.10custom-gt #4 SMP Mon Nov 1 14:17:36 EST 2004 \ i686 unknown [root@cyclops root]# cat /etc/redhat-release Red Hat Linux Advanced Server release 2.1AS (Pensacola)
Machine 2 looks like this:
atlorca4:~ # uname -a Linux atlorca4 2.6.5-7.97-default #1 SMP Fri Jul 2 14:21:59 UTC 2004 \ ia64 ia64 ia64 GNU/Linux atlorca4:~ # cat /etc/SuSE-release SUSE LINUX Enterprise Server 9 (ia64) VERSION = 9
The following representations outline the two servers within the SAN.
First, Machine 1 (Cyclops):
(Cyclops) Has two Emulex LP8000 HBAs |-LP8000-|-WWN 10000000c9241327 ----> FCID 0x7b0f00 on Brocade 28000 Storage location for Brocade 28000 Domain 0x7b Brocade 28000 Domain 0x7b port 0 -->--ISL --> Domain 0x78 Brocade 2800 \ Port 1 Domain 0x78 Brocade 2800 port 5 connects to >--- Storage array |-LP8000-|-WWN 10000000c9286bda --> FCID 0x7f0d00 on Brocade 28000 Storage location for Brocade 28000 Domain 0x7f Two ISL hopes: Brocade 28000 Domain 0x7f port 0 -->--ISL --> Domain 0x7b Brocade 28000 \ port 1, then port 0 -->--ISL --> Domain 0x78 Brocade 2800 Port 1 Domain 0x78 Brocade 2800 port 5 connects to >--- Storage array
This design is nothing more than an example of fault-tolerant Host Bus Adapter (HBA). If we lose the storage port, our host loses access to the storage.
Then we have Machine 2 (atlorca4):
|-LP9802-|-WWN 10000000c93d3fc5 --> FCID 0x652d13 on Mcdata 6064 director \ port 41 (2d hex = 45 dec subtract 4 = 41)
This calculation works on any McDATA switch, calculating the port number from the FCID area field. Many tricks exist for different switches, but they are beyond the scope of this chapter.
As you can see in the previous example, the storage array plugs into port 41 on FCID 0x652b13 of McDATA 6064, yielding 100% locality for this host.