Tuesday, 3 December 2013

VMware and ESXi with 4k Disks

EqualLogic firmware 7.0.0 now gives us the option to create volumes with 4k sectors rather than the legacy 512e sector size. I thought it would be interesting to create two EqualLogic volumes, one 4k, one 512e. Then create to VMs and IO meter to see if there are any performance gains.

The two volumes could be seen by the ESXi 5.5 host but 

I am surprised that considering 4096 byte sectors have been around since 2010 that VMware has no compatibility for this disk format.

To conclude:

ESXi + 4K disks = :(

1 comment:

  1. Not to be a stickler but actually the 512e block size was only introduced after the 4K was introduced due to the legacy(which are not really legacy) applications and operating systems which do not yet have drivers to support the 4k block size. So 512e was introduced to emulate the 512 sectors to the logical while the physical remains 4k. Problem with this configuration is that the emulation causes a lot of overhead as it's writing chunks of 512 to DRAM and then moves it to disk as a 4K chunk. This causes a lot of performance issues in VMware storage I/O latency and VMFS partitioning. I just encountered an issue with a new R730xd server that was shipped with 4Kn drives and learned the hard way how ESXi and vCenter dont play nice with 4k block/sector sizes.