dbs

package module
v0.0.0-...-2238e6b Latest Latest
Warning

This package is not in the latest version of its module.

 Go to latest Published: Oct 23, 2024 License: Apache-2.0 Imports: 8 Imported by: 0

README

Direct Block Store

A library for maintaining virtual volumes on top of a physical block device (or file). Snapshots supported. Command-line utility for query and management operations included.

Build with go build, test with go test -p 1, read the docs with godoc.

Documentation

Overview

A library for maintaining virtual volumes on top of a physical block device (or file). Snapshots supported. Command-line utility for query and management operations included.

Device layout:

  • Bytes [0, 4096) contain the the superblock
  • Bytes [4096, ExtentOffset) hold the volume and snapshot metadata (ExtentOffset is block aligned)
  • Bytes [ExtentOffset, DataOffset) hold the extent metadata (DataOffset is extent aligned)
  • Bytes [DataOffset, DeviceSize) hold the data

Index

Constants

View Source 
const (
	MAGIC   = "DBS@393!"
	VERSION = 0x00010000

	MAX_VOLUMES          = 256
	MAX_SNAPSHOTS        = 65535
	MAX_VOLUME_NAME_SIZE = 255

	BLOCK_SIZE           = 4096
	EXTENT_SIZE          = 1048576 // 1 MB
	EXTENT_BITMAP_SIZE   = 32
	BLOCK_BITS_IN_EXTENT = 8
	BLOCK_MASK_IN_EXTENT = 0xFF
)
View Source 
const (
	EXTENT_BATCH = 65536
)
View Source 
const (
	SIZEOF_EXTENT_METADATA = 6 + EXTENT_BITMAP_SIZE
)

Variables

This section is empty.

Functions

func CloneSnapshot 

func CloneSnapshot(device string, newVolumeName string, snapshotId uint) error

func CreateSnapshot 

func CreateSnapshot(device string, volumeName string) error

func CreateVolume 

func CreateVolume(device string, volumeName string, volumeSize uint64) error

func DeleteSnapshot 

func DeleteSnapshot(device string, snapshotId uint) error

func DeleteVolume 

func DeleteVolume(device string, volumeName string) error

func InitDevice 

func InitDevice(device string) error

func RenameVolume 

func RenameVolume(device string, volumeName string, newVolumeName string) error

func VacuumDevice 

func VacuumDevice(device string) error

Types

type DeviceContext 

type DeviceContext struct {
	// contains filtered or unexported fields
}

The device context holds the device file descriptor and all metadata except extents.

func GetDeviceContext 

func GetDeviceContext(device string) (*DeviceContext, error)

func NewDeviceContext 

func NewDeviceContext(device string) (*DeviceContext, error)

Initialize a new, empty device context.

func (*DeviceContext) AddSnapshot 

func (dc *DeviceContext) AddSnapshot(parentSnapshotId uint16) (uint16, error)

Add a new snapshot. Return the snapshot identifier.

func (*DeviceContext) AddVolume 

func (dc *DeviceContext) AddVolume(volumeName string, volumeSize uint64) (*VolumeMetadata, error)

Add a new volume (and corresponding snapshot). Return a pointer to the volume metadata.

func (*DeviceContext) Close 

func (dc *DeviceContext) Close() error

Close the device file descriptor.

func (*DeviceContext) CopyExtentData 

func (dc *DeviceContext) CopyExtentData(esrc uint, edst uint) error

func (*DeviceContext) CountSnapshots 

func (dc *DeviceContext) CountSnapshots(v *VolumeMetadata) uint

func (*DeviceContext) CountVolumes 

func (dc *DeviceContext) CountVolumes() uint

func (*DeviceContext) FindChildSnapshot 

func (dc *DeviceContext) FindChildSnapshot(snapshotId uint16) uint16

Find the descendant of the snapshot with the given identifier. Returns 0 if not found.

func (*DeviceContext) FindVolume 

func (dc *DeviceContext) FindVolume(volumeName string) *VolumeMetadata

Find the volume metadata for the given volume name. Returns nil if not found.

func (*DeviceContext) FindVolumeWithSnapshot 

func (dc *DeviceContext) FindVolumeWithSnapshot(snapshotId uint16) *VolumeMetadata

Find the volume metadata for the given snapshot identifier. Returns 0 if not found.

func (*DeviceContext) ReadBlockData 

func (dc *DeviceContext) ReadBlockData(data []byte, epos uint, bidx uint) error

func (*DeviceContext) ReadExtents 

func (dc *DeviceContext) ReadExtents(eb []ExtentMetadata, eidx uint) error

func (*DeviceContext) ReadMetadata 

func (dc *DeviceContext) ReadMetadata() error

func (*DeviceContext) ReadSuperblock 

func (dc *DeviceContext) ReadSuperblock() error

func (*DeviceContext) WriteBlockData 

func (dc *DeviceContext) WriteBlockData(data []byte, epos uint, bidx uint) error

func (*DeviceContext) WriteExtent 

func (dc *DeviceContext) WriteExtent(e *ExtentMetadata, eidx uint) error

func (*DeviceContext) WriteExtents 

func (dc *DeviceContext) WriteExtents(eb []ExtentMetadata, eidx uint) error

func (*DeviceContext) WriteMetadata 

func (dc *DeviceContext) WriteMetadata() error

func (*DeviceContext) WriteSuperblock 

func (dc *DeviceContext) WriteSuperblock() error

type DeviceInfo 

type DeviceInfo struct {
	Version                string
	DeviceSize             uint64
	TotalDeviceExtents     uint
	AllocatedDeviceExtents uint
	VolumeCount            uint
}

func GetDeviceInfo 

func GetDeviceInfo(device string) (*DeviceInfo, error)

type DirectFile 

type DirectFile struct {
	*os.File
	Name string
}

Wrapper to file object supporting direct I/O

func NewDirectFile 

func NewDirectFile(name string, flag int, perm os.FileMode) (*DirectFile, error)

func (*DirectFile) Close 

func (file *DirectFile) Close() error

func (*DirectFile) ReadAt 

func (file *DirectFile) ReadAt(data []byte, offset uint64) (int, error)

Read using direct I/O

func (*DirectFile) Size 

func (file *DirectFile) Size() (int64, error)

func (*DirectFile) WriteAt 

func (file *DirectFile) WriteAt(data []byte, offset uint64) (int, error)

Write using direct I/O

type ExtentMap 

type ExtentMap struct {
	// contains filtered or unexported fields
}

Map of the whole volume. Empty extents have an empty snapshot identifier. The extent bitmap is used to speed up operations.

func GetSnapshotExtentMap 

func GetSnapshotExtentMap(dc *DeviceContext, deviceSize uint64, snapshotId uint16) (*ExtentMap, error)

Get the map of a specific snapshot.

func GetVolumeExtentMap 

func GetVolumeExtentMap(dc *DeviceContext, deviceSize uint64, snapshotId uint16) (*ExtentMap, error)

Get the map of a volume starting at a snapshot and including all ancestors.

func (*ExtentMap) ClearAll 

func (em *ExtentMap) ClearAll() error

Clear all metadata included in the map.

func (*ExtentMap) CopyAllToSnapshot 

func (em *ExtentMap) CopyAllToSnapshot(snapshotId uint16) error

Copy the whole map to another snapshot.

func (*ExtentMap) CopyExtentToSnapshot 

func (em *ExtentMap) CopyExtentToSnapshot(eidx uint32, snapshotId uint16) error

Copy over all data from an extent to another snapshot and update the map.

func (*ExtentMap) MergeAllInto 

func (em *ExtentMap) MergeAllInto(emdst *ExtentMap, snapshotId uint16) error

Clear all metadata included in the map.

func (*ExtentMap) NewExtentToSnapshot 

func (em *ExtentMap) NewExtentToSnapshot(eidx uint32, snapshotId uint16) error

Allocate a new extent into the map.

func (*ExtentMap) WriteExtent 

func (em *ExtentMap) WriteExtent(eidx uint32) error

Write extent metadata to the device.

type ExtentMetadata 

type ExtentMetadata struct {
	SnapshotId  uint16
	ExtentPos   uint32
	BlockBitmap [EXTENT_BITMAP_SIZE]byte
}

type SnapshotInfo 

type SnapshotInfo struct {
	SnapshotId       uint
	ParentSnapshotId uint
	CreatedAt        time.Time
}

func GetSnapshotInfo 

func GetSnapshotInfo(device string, volumeName string) ([]SnapshotInfo, error)

type SnapshotMetadata 

type SnapshotMetadata struct {
	ParentSnapshotId uint16
	CreatedAt        int64
}

type Superblock 

type Superblock struct {
	Magic                  [8]byte
	Version                uint32 // 16-bit major, 8-bit minor, 8-bit patch
	AllocatedDeviceExtents uint32
	DeviceSize             uint64
}

type VolumeContext 

type VolumeContext struct {
	// contains filtered or unexported fields
}

func OpenVolume 

func OpenVolume(device string, volumeName string) (*VolumeContext, error)

func (*VolumeContext) CloseVolume 

func (vc *VolumeContext) CloseVolume() error

func (*VolumeContext) ReadAt 

func (vc *VolumeContext) ReadAt(data []byte, offset uint64) error

func (*VolumeContext) ReadBlock 

func (vc *VolumeContext) ReadBlock(data []byte, block uint64) error

func (*VolumeContext) UnmapAt 

func (vc *VolumeContext) UnmapAt(length uint64, offset uint64) error

func (*VolumeContext) UnmapBlock 

func (vc *VolumeContext) UnmapBlock(block uint64) error

func (*VolumeContext) WriteAt 

func (vc *VolumeContext) WriteAt(data []byte, offset uint64) error

func (*VolumeContext) WriteBlock 

func (vc *VolumeContext) WriteBlock(data []byte, block uint64) error

type VolumeInfo 

type VolumeInfo struct {
	VolumeName    string
	VolumeSize    uint64
	SnapshotId    uint
	CreatedAt     time.Time
	SnapshotCount uint
}

func GetVolumeInfo 

func GetVolumeInfo(device string) ([]VolumeInfo, error)

type VolumeMetadata 

type VolumeMetadata struct {
	SnapshotId uint16 // Index in snapshots table + 1
	VolumeSize uint64
	VolumeName [MAX_VOLUME_NAME_SIZE + 1]byte
}

Source Files

View all Source files

Directories

Path Synopsis
cmd
dbsctl
A command line utility exposing the query and management APIs of DBS.
 A command line utility exposing the query and management APIs of DBS.
dbssrv
NBD server for DBS.
 NBD server for DBS.

Jump to

Keyboard shortcuts

? : This menu
/ : Search site
f or F : Jump to
y or Y : Canonical URL
go.dev uses cookies from Google to deliver and enhance the quality of its services and to analyze traffic. Learn more.