gluster for sysadmins-advanced-with demo

GlusterFS and RHS for the SysAdminAn In-Depth Look and Demo

Dustin L. Black, RHCASr. Technical Account Manager & Team LeadRed Hat Global Support Services

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Dustin L. Black, RHCASr. Technical Account ManagerRed Hat, Inc.

[email protected]@dustinlblack

My name is Dustin Black. I'm a Red Hat Certified Architect, and a Senior Technical Account Manager with Red Hat. I specialize in Red Hat Storage and GlusterFS, and I've been working closely with our partner, Intuit, on a very interesting and exciting implementation of Red Hat Storage.

#whatis TAM

Premium named-resource support

Proactive and early access

Regular calls and on-site engagements

Customer advocate within Red Hat and upstream

Multi-vendor support coordinator

High-touch access to engineering

Influence for software enhancements

NOT Hands-on or consulting

-What is a Technical Account Manager?-We provide semi-dedicated support to many of the world's largest enterprise Linux consumers.-This is not a hands-on role, but rather a collaborative support relationship with the customer.-Our goal is to provide a proactive and high-touch customer relationship with close ties to Red Hat Engineering.

Agenda

Technology Overview

Scaling Up and Out

A Peek at GlusterFS Logic

Redundancy and Fault Tolerance

Data Access

General Administration

Use Cases

Common Pitfalls

I hope to make the GlusterFS concepts more tangible. I want you to walk away with the confidence to start working with GlusterFS today.


Technology
Overview

What is GlusterFS?

Scalable, general-purpose storage platform

POSIX-y Distributed File System

Object storage (swift)

Distributed block storage (qemu)

Flexible storage (libgfapi)

No Metadata Server

Heterogeneous Commodity Hardware

Standards-Based Clients, Applications, Networks

Flexible and Agile Scaling

Capacity Petabytes and beyond

Performance Thousands of Clients

-Commodity hardware: aggregated as building blocks for a clustered storage resource.-Standards-based: No need to re-architect systems or applications, and no long-term lock-in to proprietary systems or protocols.-Simple and inexpensive scalability.-Scaling is non-interruptive to client access. -Aggregated resources into unified storage volume abstracted from the hardware.

Fuse Native

NFS

libgfapi

Samba

QEMU

application

Network Interconnect

What is Red Hat Storage?

Enterprise Implementation of GlusterFS

Software Appliance

Bare Metal Installation

Built on RHEL + XFS

Subscription Model

Storage Software Appliance

Datacenter and Private Cloud Deployments

Virtual Storage Appliance

Amazon Web Services Public Cloud Deployments

-Provided as an ISO for direct bare-metal installation.-XFS filesystem is usually an add-on subscription for RHEL, but is included with Red Hat Storage-XFS supports metadata journaling for quicker crash recovery and can be defragged and expanded online.-RHS:GlusterFS::RHEL:Fedora-GlusterFS and gluster.org are the upstream development and test bed for Red Hat Storage

release

iterate

debug

enhance

upstream

glusterfs-3.4

release

With the direct partnership between Red Hat and Intuit, we were able to save precious time and get the updated code into Intuit's hands very early.

We immediately began working this into the upstream GlusterFS project, where the effect was a significant change in the priorities of the next release.

The code was then further optimized and additional features were added. And now all of these changes are ready to benefit the community with the GlusterFS 3.4 release, and will be ready for wide enterprise support in the upcoming Red Hat Storage 2.1 product.

GlusterFS vs. Traditional Solutions

A basic NAS has limited scalability and redundancy

Other distributed filesystems limited by metadata

SAN is costly & complicated but high performance & scalable

GlusterFS =

Linear Scaling

Minimal Overhead

High Redundancy

Simple and Inexpensive Deployment

Use Cases


Common Solutions

Media / Content Distribution Network (CDN)

Backup / Archive / Disaster Recovery (DR)

Large Scale File Server

Home directories

High Performance Computing (HPC)

Infrastructure as a Service (IaaS) storage layer

Hadoop Map Reduce

Access data within and outside of Hadoop

No HDFS name node single point of failure / bottleneck

Seamless replacement for HDFS

Scales with the massive growth of big data

Technology
Stack


Terminology

Brick

A filesystem mountpoint

A unit of storage used as a GlusterFS building block

Translator

Logic between the bits and the Global Namespace

Layered to provide GlusterFS functionality

Volume

Bricks combined and passed through translators

Peer

Server running the gluster daemon and sharing volumes

-Bricks are stacked to increase capacity-Translators are stacked to increase functionality

Disk, LVM, and Filesystems

Direct-Attached Storage (DAS)-or-

Just a Bunch Of Disks (JBOD)

Hardware RAID

RHS: RAID 6 required

Logical Volume Management (LVM)

XFS, EXT3/4, BTRFS

Extended attributes support required

RHS: XFS required

-XFS is the only filesystem supported with RHS.-Extended attribute support is necessary because the file hash is stored there

Gluster Components

glusterd

Elastic volume management daemon

Runs on all export servers

Interfaced through gluster CLI

glusterfsd

GlusterFS brick daemon

One process for each brick

Managed by glusterd

Gluster Components

glusterfs

NFS server daemon

Self-heal daemon

FUSE client daemon

mount.glusterfs

FUSE native mount tool

gluster

Gluster Console Manager (CLI)

-gluster console commands can be run directly, or in interactive mode. Similar to virsh, ntpq

Data Access Overview

GlusterFS Native Client

Filesystem in Userspace (FUSE)

NFS

Built-in Service

SMB/CIFS

Samba server required; NOW libgfapi-integrated!

Gluster For OpenStack (G4O; aka UFO)

Simultaneous object-based access via Swift

NEW! libgfapi flexible abstracted storageIntegrated with upstream Samba and Ganesha-NFS

-The native client uses fuse to build complete filesystem functionality without gluster itself having to operate in kernel space. This offers benefits in system stability and time-to-end-user for code updates.

Putting it All Together

Scaling Up

Add disks and filesystems to a server

Expand a GlusterFS volume by adding bricks

XFS

Scaling Out

Add GlusterFS nodes to trusted pool

Add filesystems as new bricks

Under
the Hood


Elastic Hash Algorithm

No central metadata

No Performance Bottleneck

Eliminates risk scenarios

Location hashed intelligently on filename

Unique identifiers, similar to md5sum

The Elastic Part

Files assigned to virtual volumes

Virtual volumes assigned to multiple bricks

Volumes easily reassigned on the fly

No metadata == No Performance Bottleneck or single point of failure (compared to single metadata node) or corruption issues (compared to distributed metadata).Hash calculation is faster than metadata retrievalElastic hash is the core of how gluster scales linerally

Elastic Hash Algorithm (simplified):* hash is based on the filename* the filename gets hashed to a value* say a, b, c or d* each brich in a distributed volume hold the files for a hash-range* say brick1 has a-b, and brick2 has c-d* the hash is calculated client-side* say the filename README hashes to c* the client knows the volume layout* c is in the range c-d* the range c-d is located on brick2* in case of a replicated volume, a sub-volume is created* instead of locating the files on the bricks directly, theDHT-xlator assigns the hash-ranges to sub-volumes* a sub-volume acts like a brick from the point of view of DHT* the sub-volume contains the AFR-xlator, which manages the duplication* hash collisions do not matter* two filenames that hash to the same value, just land on the same brick

Translators

Modular building blocks for functionality, like bricks are for storage

Your Storage Servers are Sacred!

Don't touch the brick filesystems directly!

They're Linux servers, but treat them like appliancesSeparate security protocols

Separate access standards

Don't let your Jr. Linux admins in!A well-meaning sysadmin can quickly break your system or destroy your data

Basic Volumes


Distributed Volume

Files evenly spread across bricks

Similar to file-level RAID 0

Server/Disk failure could be catastrophic

Replicated Volume

Copies files to multiple bricks

Similar to file-level RAID 1

Striped Volumes

Individual files split among bricks

Similar to block-level RAID 0

Limited Use Cases HPC Pre/Post Processing

Limited Read/Write performance increase, but in some cases the overhead can actually cause a performance degredation

Layered
Functionality


Distributed Replicated Volume

Distributes files across replicated bricks

Distributed Striped Volume

Files striped across two or more nodes

Striping plus scalability

Striped Replicated Volume

RHS 2.0 / GlusterFS 3.3+

Similar to RAID 10 (1+0)

-Graphic is wrong ---Replica 0 is exp1 and exp3-Replica 1 is exp2 and exp4

Distributed Striped Replicated Volume

RHS 2.0 / GlusterFS 3.3+

Limited Use Cases Map Reduce

This graphic from the RHS 2.0 beta documentation actually represents a non-optimal configuration. We'll discuss this in more detail later.

Asynchronous Replication


Geo Replication

Asynchronous across LAN, WAN, or Internet

Master-Slave model -- Cascading possible

Continuous and incremental

Data is passed between defined master and slave only

When you configure geo-replication, you do so on a specific master (or source) host, replicating to a specific slave (or destination) host. Geo-replication does not scale linearly since all data is passed through the master and slave nodes specifically.

Because geo-replication is configured per-volume, you can gain scalability by choosing different master and slave geo-rep nodes for each volume.

?

Geo-Replication was in need of a whole new approach. At the time, multi-master replication was on the product roadmap, pending a future release. But as it turned out, Intuit had already resolved the mult-master limitation with a novel approach utilizing their Cassandra NoSQL system. I'll let Mohit describe that in more detail in a moment.

NEW! Distributed Geo-Replication

In a very short time, Red Hat engineers were able to characterize the limitations that Intuit was encountering, and propose new code to address them a completely re-designed Geo-Replication stack.

Where the traditional GlusterFS Geo-Replication code relied on a serial stream between only two nodes, the new code employed an algorithm that would divide the replication workload between all members of the volumes on both the sending and receiving sides.

Additionally, the new code introduced an improved filesystem scanning mechanism that was significantly more efficient for Intuit's small-file use case.

Distributed Geo-Replication

Drastic performance improvements

Parallel transfers

Efficient source scanning

File type/layout agnostic

Available now in RHS 2.1

Planned for GlusterFS 3.5




Distributed Geo-Replication

Drastic performance improvements

Parallel transfers

Efficient source scanning

File type/layout agnostic

Perhaps it's not just for DR anymore...http://www.redhat.com/resourcelibrary/case-studies/intuit-leverages-red-hat-storage-for-always-available-massively-scalable-storage




Replicated Volumes vs Geo-replication

Replicated VolumesGeo-replication

Mirrors data across clustersMirrors data across geographically distributed clusters

Provides high-availabilityEnsures backing up of data for disaster recovery

Synchronous replication (each and every file operation is sent across all the bricks)Asynchronous replication (checks for the changes in files periodically and syncs them on detecting differences)

Data Access


GlusterFS Native Client (FUSE)

FUSE kernel module allows the filesystem to be built and operated entirely in userspace

Specify mount to any GlusterFS server

Native Client fetches volfile from mount server, then communicates directly with all nodes to access data

Recommended for high concurrency and high write performance

Load is inherently balanced across distributed volumes

-Native client will be the best choice when you have many nodes concurrently accessing the same data-Client access to data is naturally load-balanced because the client is aware of the volume structure and the hash algorithm.

NFS

Standard NFS v3 clients

Standard automounter is supported

Mount to any server, or use a load balancer

GlusterFS NFS server includes Network Lock Manager (NLM) to synchronize locks across clients

Better performance for reading many small files from a single client

Load balancing must be managed externally

...mount with nfsvers=3 in modern distros that default to nfs 4The need for this seems to be a bug, and I understand it is in the process of being fixed.

NFS will be the best choice when most of the data access by one client and for small files. This is mostly due to the benefits of native NFS caching.

Load balancing will need to be accomplished by external mechanisms

NEW! libgfapi

Introduced with GlusterFS 3.4

User-space library for accessing data in GlusterFS

Filesystem-like API

Runs in application process

no FUSE, no copies, no context switches

...but same volfiles, translators, etc.

...mount with nfsvers=3 in modern distros that default to nfs 4The need for this seems to be a bug, and I understand it is in the process of being fixed.

NFS will be the best choice when most of the data access by one client and for small files. This is mostly due to the benefits of native NFS caching.

Load balancing will need to be accomplished by external mechanisms

SMB/CIFS

NEW! In GlusterFS 3.4 Samba + libgfapi

No need for local native client mount & re-export

Significant performance improvements with FUSE removed from the equation

Must be setup on each server you wish to connect to via CIFS

CTDB is required for Samba clustering

-Use the GlusterFS native client first to mount the volume on the Samba server, and then share that mount point with Samba via normal methods.-GlusterFS nodes can act as Samba servers (packages are included), or it can be an external service.-Load balancing will need to be accomplished by external mechanisms

Demo Time!


General
Administration


Preparing a Brick

# lvcreate -L 100G -n lv_brick1 vg_server1# mkfs -t xfs -i size=512 /dev/vg_server1/lv_brick1# mkdir /brick1# mount /dev/vg_server1/lv_brick1 /brick1# echo '/dev/vg_server1/lv_brick1 /brick1 xfs defaults 1 2' >> /etc/fstab

An inode size smaller than 512 leaves no room for extended attributes (xattr). This means that every active inode will require a separate block for these. This has both a performance hit as well as a disk space usage penalty.

Adding Nodes (peers) and Volumes

gluster> peer probe server3gluster> peer statusNumber of Peers: 2

Hostname: server2Uuid: 5e987bda-16dd-43c2-835b-08b7d55e94e5State: Peer in Cluster (Connected)

Hostname: server3Uuid: 1e0ca3aa-9ef7-4f66-8f15-cbc348f29ff7State: Peer in Cluster (Connected)

gluster> volume create my-dist-vol server2:/brick2 server3:/brick3gluster> volume info my-dist-volVolume Name: my-dist-volType: DistributeStatus: CreatedNumber of Bricks: 2Transport-type: tcpBricks:Brick1: server2:/brick2Brick2: server3:/brick3gluster> volume start my-dist-vol

Distributed Volume

Peer Probe

-peer status command shows all other peer nodes excludes the local node-I understand this to be a bug that's in the process of being fixed

Distributed Striped Replicated Volume

gluster> volume create test-volume replica 2 stripe 2 transport tcp \server1:/exp1 server1:/exp2 server2:/exp3 server2:/exp4 \server3:/exp5 server3:/exp6 server4:/exp7 server4:/exp8Multiple bricks of a replicate volume are present on the same server. This setup is not optimal.Do you still want to continue creating the volume? (y/n) yCreation of volume test-volume has been successful. Please start the volume to access data.

volume info test-volume

Volume Name: test-volumeType: Distributed-Striped-ReplicateVolume ID: 8f8b8b59-d1a1-42fe-ae05-abe2537d0e2dStatus: CreatedNumber of Bricks: 2 x 2 x 2 = 8Transport-type: tcpBricks:Brick1: server1:/exp1Brick2: server2:/exp3Brick3: server1:/exp2Brick4: server2:/exp4Brick5: server3:/exp5Brick6: server4:/exp7Brick7: server3:/exp6Brick8: server4:/exp8

gluster> volume create test-volume stripe 2 replica 2 transport tcp \server1:/exp1 server2:/exp3 server1:/exp2 server2:/exp4 \server3:/exp5 server4:/exp7 server3:/exp6 server4:/exp8Creation of volume test-volume has been successful. Please start the volume to access data.

-Brick order is corrected to ensure replication is between bricks on different nodes.-Replica is always processed first in building the volume, regardless of whether it's before or after stripe on the command line.-So, a 'replica 2' will create the replica between matching pairs of bricks in the order that the bricks are passed to the command. 'replica 3' will be matching trios of bricks, and so on.

Manipulating Bricks in a Volume

gluster> volume add-brick my-dist-vol server4:/brick4

gluster> volume remove-brick my-dist-vol server2:/brick2 startgluster> volume remove-brick my-dist-vol server2:/brick2 statusNode Rebalanced-files size scanned failures status--------- ----------- ----------- ----------- ----------- ------------localhost 16 16777216 52 0 in progress192.168.1.1 13 16723211 47 0 in progressgluster> volume remove-brick my-dist-vol server2:/brick2 commit

gluster> volume rebalance my-dist-vol fix-layout start

gluster> volume rebalance my-dist-vol startgluster> volume rebalance my-dist-vol statusNode Rebalanced-files size scanned failures status--------- ----------- ----------- ----------- ----------- ------------localhost 112 15674 170 0 completed10.16.156.72 140 3423 321 2 completed

Must add and remove in multiples of the replica and stripe counts

Migrating Data / Replacing Bricks

gluster> volume replace-brick my-dist-vol server3:/brick3 server5:/brick5 startgluster> volume replace-brick my-dist-vol server3:/brick3 server5:/brick5 statusCurrent File = /usr/src/linux-headers-2.6.31-14/block/Makefile Number of files migrated = 10567Migration completegluster> volume replace-brick my-dist-vol server3:/brick3 server5:/brick5 commit

Volume Options

gluster> volume set my-dist-vol auth.allow 192.168.1.*gluster> volume set my-dist-vol auth.reject 10.*

gluster> volume set my-dist-vol nfs.volume-access read-onlygluster> volume set my-dist-vol nfs.disable on

gluster> volume set my-dist-vol features.read-only ongluster> volume set my-dist-vol performance.cache-size 67108864


NFS

Auth

Other advanced options

Volume Top Command


gluster> volume top my-dist-vol read brick server3:/brick3 list-cnt 3Brick: server:/export/dir1==========Read file stats========

read filenamecall count

116 /clients/client0/~dmtmp/SEED/LARGE.FIL

64 /clients/client0/~dmtmp/SEED/MEDIUM.FIL

54 /clients/client2/~dmtmp/SEED/LARGE.FIL

Many top commands are available for analysis of files, directories, and bricks

Read and write performance test commands availablePerform active dd tests and measure throughput

Volume Profiling


gluster> volume profile my-dist-vol startgluster> volume profile my-dist-vol infoBrick: Test:/export/2Cumulative Stats:

Block 1b+ 32b+ 64b+Size:Read: 0 0 0Write: 908 28 8

...

%-latency Avg- Min- Max- calls Foplatency Latency Latency ___________________________________________________________4.82 1132.28 21.00 800970.00 4575 WRITE5.70 156.47 9.00 665085.00 39163 READDIRP11.35 315.02 9.00 1433947.00 38698 LOOKUP11.88 1729.34 21.00 2569638.00 7382 FXATTROP47.35 104235.02 2485.00 7789367.00 488 FSYNC

------------------

Duration : 335

BytesRead : 94505058

BytesWritten : 195571980

??where is this stored, and how does it impact performance when on??

Common
Pitfalls


Split-Brain Syndrome

Communication lost between replicated peers

Clients write separately to multiple copies of a file

No automatic fix

May be subjective which copy is right ALL may be!

Admin determines the bad copy and removes it

Self-heal will correct the volumeTrigger a recursive stat to initiate

Proactive self-healing in RHS 2.0 / GlusterFS 3.3

Quorum Enforcement

Disallows writes (EROFS) on non-quorum peers

Significantly reduces files affected by split-brain

Preferred when data integrity is the priority

Not preferred when application integrity is the priority

NEW! Server-Side Quorum

In GlusterFS 3.3

Client-side

Replica set level

NOW in GlusterFS 3.4

Server-side

Cluster-level (glusterd)

This quorum is on the server-side i.e. in glusterd. Whenever the glusterdon a machine observes that the quorum is not met, it brings down the bricksto prevent data split-brains. When the network connections are brought backup and the quorum is restored the bricks in the volume are brought back up.In glusterd commands to configure the quorum values are provided which arelisted in the sections below. When the quorum is not met for a volume, anycommands that update the volume configuration or peer addition or detachare not allowed.

Do it!


Do it!

Build a test environment in VMs in just minutes!

Get the bits:

Fedora 19 has GlusterFS packages natively

RHS 2.1 ISO available on Red Hat Portal

Go upstream: www.gluster.org

Amazon Web Services (AWS)Amazon Linux AMI includes GlusterFS packages

RHS AMI is available

Thank You!

[email protected]

[email protected]

RHS:www.redhat.com/storage/

GlusterFS:www.gluster.org

TAM: access.redhat.com/support/offerings/tam/

@Glusterorg@RedHatStorage

GlusterRed Hat Storage

Slides Available at: http://people.redhat.com/dblack


Question notes:

-Vs. CEPH-CEPH is object-based at its core, with distributed filesystem as a layered function. GlusterFS is file-based at its core, with object methods (UFO) as a layered function.-CEPH stores underlying data in files, but outside the CEPH constructs they are meaningless. Except for striping, GlusterFS files maintain complete integrity at the brick level.-With CEPH, you define storage resources and data architecture (replication) separate, and CEPH actively and dynamically manages the mapping of the architecture to the storage. With GlusterFS, you manually manage both the storage resources and the data architecture.

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