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VMDK vs qcow2

A side-by-side feature comparison.

Summary

VMDK is the universal hypervisor disk format; qcow2 is the QEMU/KVM native one. Both support sparse files and snapshots, but qcow2's richer cluster-level features (encryption, deduplication, internal snapshots) make it the default choice on Linux KVM.

Bottom line: qcow2 on KVM. VMDK when you need to share disks with VMware or distribute appliances.

Feature comparison

Feature VMDK QCOW2 (QEMU Copy-On-Write)
Native to VMware QEMU/KVM
Snapshots External (delta files) Internal
Encryption Limited LUKS-equivalent
Sparse Yes Yes
Compression streamOptimized only Per-cluster zlib
Cross-hypervisor support Universal Convert with qemu-img

About VMDK

VMDK is VMware's virtual disk format and the most portable VM disk in the industry. Public cloud OVF templates and Vagrant boxes ship as VMDKs because every hypervisor reads them. The streamOptimized variant uses per-chunk zlib so VMDKs can be downloaded over HTTP and streamed straight into a hypervisor without intermediate decompression.

Read the full VMDK guide →

About QCOW2 (QEMU Copy-On-Write)

QCOW2 (QEMU Copy-On-Write version 2) is the native virtual disk format of QEMU and the default for KVM-based clouds like OpenStack. It supports snapshots, internal compression, AES encryption, and copy-on-write backing files for cheap VM cloning.

Read the full QCOW2 (QEMU Copy-On-Write) guide →

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