Tech: Problems with VMware ESX Server and EMC CLARiiON

The Lone Sysadmin published an interesting report about Logical Block Addressing (LBA) issues with ESX Server 2.x (or ESX Server 3.0 beta) and EMC CLARiiON CX700s:

The problems I was having were caused by logical block addressing (LBA), a feature of the PC BIOS that reworks the disk geometry so that a disk always appears to have 1024 tracks/cylinders and 63 sectors per track/cylinder.

With VMware you get hit twice. Each virtual machine emulates LBA, too, and so each virtual machine is also misaligned by default. Coupled with the misalignment at the VMFS level you have a mess, and each I/O request made by a VM results in a lot of work at the lower level, as well as a lower cache hit ratio and fewer chances for I/O aggregation, write/read combining, etc…

Read the whole article at source.

Thanks to VMTN Blog for the news.