If you use or are interested in VMware ESX 3.x and iSCSI, you simply must go read  Chad Sakac’s post on the topic. Co-written with just about everyone in the industry (including EMC, VMware, NetApp, Dell/EqualLogic, and HP/Lefthand), Chad has put together a “cheat sheet” on the ins and outs of iSCSI connectivity and performance in ESX 3.x.

Top takeaways (and I’ve been preaching about these for a while myself, too!)

• Ethernet link aggregation doesn’t buy you anything in iSCSI environments
• iSCSI HBA’s don’t buy you much other than boot-from-SAN in ESX, either
• The most common configuration (ESX software iSCSI) is limited to about 160 MB/s per iSCSI target over one-gigabit Ethernet, but that’s probably fine for most applications
• Adding multiple iSCSI targets adds performance across the board, but configurations vary by array
• Maximum per-target performance comes from guest-side software iSCSI, which can make use of multiple Ethernet links to push each array as fast as it can go

Thanks for putting together such a great article, guys!