{"id":13179,"date":"2012-07-26T09:00:00","date_gmt":"2012-07-26T08:00:00","guid":{"rendered":"https:\/\/aidanfinn.com\/?p=13179"},"modified":"2012-07-26T09:00:00","modified_gmt":"2012-07-26T08:00:00","slug":"why-windows-server-2012-hyper-v-vhdx-4k-alignment-is-so-important","status":"publish","type":"post","link":"https:\/\/aidanfinn.com\/?p=13179","title":{"rendered":"Why Windows Server 2012 Hyper-V VHDX 4K Alignment Is So Important"},"content":{"rendered":"

Back in 2009, ZDNet asked if we were ready for 4K sector drives<\/a>.\u00a0 That was because the storage industry is shifting from 512 byte sector drives to 4K sector drives.\u00a0 And that is going to cause a problem for operating systems and virtualisation that are not ready for 4K sector disks.<\/p>\n

To smooth the shift, the storage industry is giving us Advanced Format 512e disks that are physically 4096 byte (4K) sector aligned but emulate 512 byte disks in their firmware.\u00a0 This wiki page<\/a> describes how this emulation works.\u00a0 Note that the read process should<\/em> not cause performance issues (but might) but the emulated read-modify-write (RMW \u2013 4K is read in, 512 bytes are modified in the 4K, disk is spun, and old 4K is overwritten) process could actually have a significant performance price (Microsoft say<\/a> 30% to 80%).<\/p>\n

\"4K<\/p>\n

The following OS\u2019s support<\/a> 512e drives:<\/p>\n