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README

Zero-OS 0-Disk

Zero-OS 0-Disk is about the components that allow to create and use block devices (vdisks) from within virtual machines hosted on a Zero-OS node.

A vdisk can be deduped, have various block sizes and depending on the underlying storage (1) cluster, have different speed characteristics.

Following vdisks types are supported:

• Boot: redundant disk that can be initialized based on a boot image (template). Boot disks should only be used for the operating system and applications installed on the operating system. Performance of boot disks is not optimized because that defeats their purpose.
• DB: redundant disk optimized for performant block storage. DB disks should be used for running reliable high IO intensive workloads such as databases, key value stores, ...
• Cache: persistent non-redundant disk optimized for performant block storage. Cache disks should be used for high IO intensive workloads which don't need to be highly reliable.
• Tmp: non-persistent non-redundant disk optimized for performant block storage. Content in tmp disks is only available while mounted. Tmp disks should be used for swap and mounts in /tmp.

VDisk type	Redundant	Persistent	Template Support	Rollback	Performance Optimized
Boot	yes	yes	yes	yes	no
DB	yes	yes	no	yes	yes
Cache	no	yes	no	no	yes
Tmp	no	no	no	no	yes

Zero-OS block storage is implemented in the zero-os/0-Disk repository on GitHub.

Components:

• NBD Server: a network block device (NBD) server to expose the vdisks to virtual machines
• TLOG Server/Client: a transaction log (3) server and client to record block changes
• zeroctl: a command line tool to manage and discover vdisks

See the Table of Contents for all documentation.

See the Glossary as a reference for terminology specific to this project.