SNAPSHOTS IN RED HAT STORAGE SERVER/GlusterFS

Anand SubramanianSenior Principal Engineer, Red Hat

Rajesh JosephPrincipal Engineer, Red Hat

AGENDA

•Introduction

•Snapshot CLI commands

•Snapshot features : user-serviceable snaps

•Snapshot recommendations

•Roadmap, Future Directions

•Q&A

RHS Overview

• Open software-defined storage solution

• Based on GlusterFS : scale-out, distributed file-system

•No external metadata servers•Scale-out with Elasticity•Extensible and modular

• RHS volume : unified namespace for the distributed file-system

• Access using GlusterFS native/FUSE, NFS, SMB and HTTP protocols

•

RHS Bricks

• A brick is the combination of a node and an export directory – for e.g. hostname:/dir

• Each brick inherits limits of the underlying filesystem

• No limit on the number bricks per node

Storage Node Storage Node Storage Node

Two Bricks One BrickThree Bricks

RHS Volume

• A volume is a logical collection of bricks.

• Volume is identified by an administrator provided name.

• Volume is a mountable entity and the volume name is provided at the time of mounting.

•mount -t glusterfs server1:/<volname> /my/mnt/point

• Bricks from the same node can be part of different volumes

Red Hat Storage Volume

RHS Volume

Storage Node Storage Node Storage Node

Brick Brick Brick Brick

Snapshots in RHS

•Volume level snapshots

•LVM2 based

•Operates only on thin-provisioned volumes

•Snapshots themselves are thin-provisioned snapshot volumes

•A GlusterFS volume snapshot consists of snapshots of the individual bricks making up the volume

•Snapshot of a GlusterFS volume is also a GlusterFS volume

•Crash consistent

Logical Volume Manager (LVM) 2

•Creates a layer of abstraction over physical storage (PVs)

•Volume Groups •One or more physical disks

•Logical Volumes•Thinly provisioned

Thinly Provisioned LVM2 Volume & Snapshot

Storage devices

Thin LV SnapshotThin LV Thin LV

Thin Pool Thin Pool

Volume Group

Red Hat Storage Snapshot

RHS Volume

Storage Node Storage Node

Brick1 Brick2 Brick3 Brick4

Brick1_s1 Brick2_s1Brick4_s1Brick3_s1

Snapshot volume

AGENDA

•Introduction

•Snapshot CLI commands

•Snapshot features : user-serviceable snaps

•Snapshot recommendations

•Roadmap, Future Directions

•Q&A

SNAPSHOT CLI COMMANDS

•Create

•Restore

•Delete

•List

•Info

•Status

•Config

Snapshot Create

gluster snapshot create <snap­name> <vol­name(s)> [description <description>] [force]

•Create snapshot of an active snapshot volume

•Snapshot is allowed if brick quorum is met

•Snapshot volume is started by default

Snapshot Restore

gluster snapshot restore <snap­name>

•Volume should be stopped

•Brick paths will be changed after restore

•Once the snapshot is restored it will be deleted

Snapshot Delete

gluster snapshot delete <snap­name>

•Snapshot including the backend lvm will be removed

•Snapshot volume will be stopped before deleting it.

Snapshot List

gluster snapshot list [vol­name]

•List will display only snap names

Snapshot Info

gluster snapshot info [(<snap­name> | volume <vol­name>)]

•Info will provide details about the snap

Snapshot Status

gluster snapshot status [(<snap­name> | volume <vol­name>)]

•Status will provide brick details and backend data (LVM)

Snapshot config

gluster snapshot config [vol­name]

gluster snapshot config [vol­name] [<snap­max­hard­limit> <count>] [<snap­max­

soft­limit> <percentage>] [force]

•Configure maximum allowed snapshot for a volume

•Configure maximum allowed snapshot for the entire cluster

•Display the current configuration

AGENDA

•Introduction

•Snapshot CLI commands

•Snapshot features : user-serviceable snaps

•Snapshot recommendations

•Roadmap, Future Directions

•Q&A

User Serviceable Snapshots in RHS

•Users can access snapshots of a volume without admin intervention ; ease of access

•“Wormhole” into the past – into any snapshot volume

•Read-only snapshot volumes

•cd to “.snaps” virtual directory anywhere in the filesystem to access your data

User Serviceable Snapshots in RHS

• cd  $HOME (say, /home/john)

• ls 

dir1/  dir2/  file1

• cd dir2

• ls 

file10 file15 

• cd .snaps

• ls 

nightly.0/  nightly.1/  weekly.0/  weekly.1/

• cd weekly.0/ 

User Serviceable Snapshots in RHS

• pwd 

/home/john/dir2/.snaps/weekly.0/

•ls

file10 file20 file30 file40

• cp ­p file30 $HOME/dir2/

AGENDA

•Introduction

•Snapshot CLI commands

•Snapshot features : user-serviceable snaps

•Snapshot recommendations

•Roadmap, Future Directions

•Q&A

Recommendations

•Each volume brick should be on an independent thinly provisioned volume.

•Brick LVM should not be used for any other purpose.

•All the snapshot of the brick will be created on same thin pool.

•Thin pool should have sufficient free space.

Older Gluster Volume Configuration

Storage devices

LV

Volume Group

Brick1

Brick2

LV

mount

New Volume Configuration for Snapshot

Storage devices

Thin LV

Volume GroupBrick1 Brick2

Thin LV

mount

Thin Pool

mount

Snapshot Future

•Snapshot of multiple volume

•Snapshot scheduling

•Geo-replication with snapshot

•Pluggable snapshot support : Btrfs

•Writable snapshots

•Support for snap aware applications

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