snia-ssm-slides-2003-04-13

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1 Copyright © 2000,2003, Storage Networking Industry Association

Obligatory rubric

Copyright © 2000,2003 Storage Networking

Industry Association (SNIA).

SNIA-TC members may use this materialfreely; all others must conform to usage

notes in the speaker noted for this slide.

See SNIA-SSM-colors.ppt for printing andcolor/graphics conventions.

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Copyright © 2000,2003, Storage Networking Industry Association

SNIA shared-storage model

A work in progress …

An architectural overview

This revision:

• 2001-06-05 last content update

• 2003-04-13 last graphics update

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Contents

Purpose

The SNIA storage model

Layers, functions, and services

Networks and interfaces

Applying the SNIA storage model

Common storage architectures

Conclusions

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Benefits

A common ―architecture vocabulary‖

Reference comparisons between common

solutions

Help to align the industry

Customers can better structure their choices

Vendors can better explain their differences

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What the model is and is not

It is not:

A specification, an architecture, a design, a product,

a recommendation, or an installation

It is:

A framework that captures the functional layers andproperties of a storage system

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Classic storage model

Application

Storage domain: “anything goes!”

Network? Appliance?

Data

mover? Array?

NAS?

JBOD?

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File/record layer

Block layer

Storage devices (disks, …)

Database

(dbms)

File system

(FS)

The SNIA shared storage model

S t o r a g e d o m a i n

S

e r v i c e s

Network

Host

Device

Block

aggregation

Application

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File/record layer

The SNIA storage model:File/record layer

Database

(dbms)

File system

(FS)

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The SNIA storage model:File/record layer — functions

Aka ―access methods‖ File system, database

Primary responsibility: packing manysmaller things into a few larger ones Fine-grain naming, space allocation

Secondary responsibilities Caching for performance Coherency in distributed systems

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The SNIA storage model:Block layer

Block layer


Block aggregation

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The SNIA storage model:Block layer — functions

Storage devices – storing data disk drives, tape drives, solid-state disks, …

Block aggregation – address mapping in-SN aggregation, or “virtualization”

slicing & concatenation, striping

local & remote mirroring, RAID-n

Examples

volume managers disk array LUs

Secondary responsibilities caching

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File/record layer

Database

(dbms)

File system

(FS)

Block layer

The SNIA storage model:Access path examples


Block aggregation

Note: all 8

possible paths

can be used!

Application

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Block layer

Block-mapping functions:

what can be done

Functional decomposition:where it can be done

Sample architectures

Block layer


Blockaggregation

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Block layer What can be done

Space management

making a large store from many small ones

packing many small stores into one large one

Striping

for performance (load balancing, throughput)

Redundancy

full (local & remote mirroring, RAID-1, -10, …)

partial (RAID-3, -4, -5, …)

point-in-time copy

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Block layer Where it can be done

Host-side logical volume managers

device drivers, HBAs

SN-based HBAs, specialized SN appliances

Device-based

array controllers (e.g., RAID) disk controllers (e.g., sparing)

Storage devices

Blockaggregation

Network

Host

Device

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Block layer How it is done

Building blocks input: vector of blocks

output: vector of blocks

Result: building blockscan be stacked enables the 3 layer model for the

block layer

layers can be nested on one another

could be extended to more layers

… …

…

Blockaggregation

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Device block-aggregation

Network block-aggregation

Host block-aggregation

Block layer Sample architectures

Application

H o s t . w i t h L V M

( + s o f t w a r e

R A I D ? )

1. Direct-attach

Disk array

SN

H o s

t

w i t h L V M

2. SN-attach

F i l e / r e c o r d

l a y e r

B l o c k

l a y e r

3. SN aggregation

Aggregation

appliance

H

o s t ,

n o

L V M

Storage devices

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File/record layer

Byte-mapping functions:

what can be done

Functional decomposition:where it can be done

Sample architectures

File/record layer Database(dbms)

File system(fs)

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File/record layer What can be done

Database management systems

tuples tables

tables table-spaces

table-spaces volume

File systems

files volume

New types

http caches: a kind of distributed file system?

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device

File/record layer Where it can be done

Host-side file systems and databases

NFS, CIFS, etc. are client-server

splits inside the file system

SN-based NAS head

Device-based NAS functions in array box

NAS

H o s t w i t h

N F S / C I F S

c l i e n t

H o s t w i t h l o c a l

F S / d b m s

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File/record layer


a n d s o f t w

a r e R A I D

1. Direct-attach


l a y e r

B l o c k

l a y e r

NAS

server

4. NAS server


Disk array

2. SN-attach

Host3. NAS head

NAS

head

Host

LAN

Application

SN

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File/record layer

Database(dbms)

File system(fs)

The SNIA storage modelA layered view

IV. Application

III. File/record layer IIIa. Database

IIIb. File system

II. Block aggregationIIa. Host

IIb. Network

IIc. DeviceI. Storage devices

Storage devices

Blockaggregation

Application

Network

Host

Device

IV

III

IIc

IIb

IIa

I

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S t o r a g e d o m a i n

File/record layer

Block layer

The SNIA storage modelServices subsystem

Application


Block aggregation

Database

(dbms)

File system

(fs)

S e r v i c e s

D i s c o

v e r y , m o n i t o r i n g

R e s o u r c e

m g m t , c o n f i g u r a

t i o n

S e

c u r i t y ,

b i l l i n g

R e d u n d a n c

y m g m t ( b a c k u p , …

)

H i g h a v a i l a b i l i t y ( f a i l - o v e r ,

… )

C a p

a c i t y p l a n n i n g

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Services

Operations off the critical path

naming, discovery, monitoring, configuration, security, billing,

redundancy management (backup, …), high availability

management (fail-over, …), capacity planning, … strong ties into system-wide management services

Vital for successful operation

and a major opportunity for SNIA …

… but not discussed further in this presentation

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Caching… can be added to almost any layer


a n d s o f t w

a r e R A I D


l a y e r

B l o c k

l a y e r

Host

NAS

head

Host


Disk array

SN

NAS

head

LAN

Ideally, caching onlyaffects performance.

But: coherencyimplications do affectmanagement(protocols, interfaces)

Application

Cache

Cache

Cache

Cache

Cacheappliance

Cache

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ClusteringInter-box aggregation


a n d s o f t w

a r e R A I D


l a y e r

B l o c k

l a y e r

Host

NAS

head

Host


Disk array

SN

NAS

head

LAN

Cluster FS

Multi-node LVM

Purposes:

• load spreading acrosspeers (scalability)

• alternate paths (highavailability, scalability)

Application

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Q: Data versus storage?

A: Putting information into containers

user: data (“learning my preferences”)

application: container (“user keystroke history”)

application: data (“user keystroke history file”) file system: container (“byte vector”)

file system: data (“a named file”)

volume system: container (“blocks in volume”)

volume system: data (“replicated, striped layout”)

disk array: container (“blocks in LU”)

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SharingContent sharing or resource sharing?

Content sharing (―logical‖, ―data‖) contents accessed and understood by multiple

clients

• e.g., file system, Oracle Parallel Server dbms some of the hard issues:

• coherency• heterogeneous data formats

Resource sharing (―container‖, ―physical‖) e.g., disk array where hosts access disjoint LUs

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SharingContent sharing and resource sharing

H o

s t

w i t h

L V M

F i l e

/ r e c o r d

l a y e r

B l o c k

l a y e r

H o

s t

w i t h

L V M

SN

NAS system

HostHost

LAN

Application

Resourcesharing

Array is

shared,

but LUs are

disjoint

Data sharing

NAS system is

shared – and so

are the files

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Storage device

Block layer

File layer

Operating System

Application

Networks and interfacesare pervasive in the model

Network or interface

Network

Bus

API

Full benefits come

only from

common, open

interfaces

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Networks and interfacesComposition and scaling

Open interfaces

allow:

1. vertical

composition

2. horizontal scaling

3. supplier

independence

Network

Bus

API

API

Network

Bus

API

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Networks and interfacesOpen interfaces require …

Well defined: functions (what they do)

interface protocols (data formats)

access protocols (system call, RPC, flow control, …)

That are: published

supported by multiple products

=> standards (which is where SNIA comes in)

Network

Bus

API

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? NAS

Q: ―SAN‖ versus ―NAS‖? A: a poorly-formed question

Q: hardware: FibreChannel vsEthernet vs InfiniBand?

Q: API: blocks vs files (aka ―NAS‖)

vs objects (OSD)?

Q: protocol: FCP vs TCP/IP vs … ?

A: (to all the above) it depends …

Storage network (SN): any (mostly) dedicated network,

installed (mostly) for storage traffic

whatever the hardware, API, or protocol

―SAN‖

FC E’net

iSCSI

F i l e s

B l o c k s

FC E’net

F i l e s

B l o c k s

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Some common storage

architectures

Mapping the SNIA model onto somecurrent implementations

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Direct-attach block storage

Disk array

H o s t ,

n o L V M

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

H o s t . w

i t h L V M

a n d s o f t w

a r e R A I D

H o

s t

w i t h

L V M

Application • Direct-attach

• Multi-attach box

E.g., SCSI

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SN-attached block storage

Disk array

H o s t ,

n o L V M

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

SN

―SN‖ = any network used for storageaccess. E.g., Fibre Channel,Ethernet, …

H o s t

w i t h

L V

M

Application

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SN-attached block storagewith metadata server

Disk array

H o s t

w i t h

L V

M

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

SNBlock-aggregationmetadata server

H o s t ,

n o L V M

Aggregation map(metadata) issupplied by anexternal server

Application

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Block storage aggregationin a storage network appliance

Disk array

SN

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

Aggregationappliance

H o

s t

w i t h

L V M

H o s t ,

n o L V M

Application aka ―SN virtualization‖

Functions: LVM, caching

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Multi-siteblock storage

Disk array

SN



Application

Disk array


H o s t .

w i t h L V M

Application

SN appliance

WAN

WAN

Host-to-host

Functions: point-in-timecopy, caching,local & remote mirroring, …

WAN

Device-to-device

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

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File server

NAS system

HostHost

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

LAN-attached―NAS‖ system

May do SN/blockaggregation, etc. insidein the NAS system box

Application

LAN

privateSN?

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File server controller (―NAS head‖)

NAS

head

Disk array

F i l e

/ r e c o r d

l

a y e r

B l o c k

l a y e r

No storage in thefile server controller box

HostHost

LAN

Application

SN

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NAS/file server metadatamanager (―asymmetric‖)

Disk array

F i l e

/ r e c o r d

l a y e r

B l o c k

l a y e r

Hosts get file meta-data from FS/NAScontroller, thenaccess the datadirectly

H o

s t . w i t h L V M

Filemetadata

Blockaccesses

FS controller canalso be NAS server

Host

LAN

SN

Application

File system

metadata

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Object-based Storage Device(OSD), CMU NASD

OSDdevice

F i l e

/ r e c o r d

l a y e r

B l o c k

l a y e r

Host

Object

metadata

Host

Application

LAN

Securitymetadata

Filemetadata

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Summary & conclusions

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File/record layer

Database(dbms)

File system(FS)

The SNIA shared storage model

S t o r a g

e d o m a i n

Block layer


S e r v i c e s

D i s c o

v e r y , m o n i t o r i n g

R e s o u r c e

m g m t , c o n f i g u r a t i o n

S e

c u r i t y ,

b i l l i n g

R e d u n d a n c y m g m t ( b a c k u p , …

)

H i g h a v a i l a b i l i t y ( f a i l - o v e r , …

)

C a p

a c i t y p l a n n i n g

Application

Network

Host

Device

Block

aggregation

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Block layer Sample architectures

H o s t . w

i t h L V M

a n d s o f t w

a r e R A I D

1. Direct-attach

SN

H o s t . w

i t h L V M

Disk array

2. SN-attach

3. SN aggregation

Aggregation

appliance

H o s t ,

n o L V M

F i l e

/ r e c o r d

l a y e r

B l o c k

l a y e r

Application

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File/record layer Sample architectures

H o s t . w

i t h L V M

a n d s o f t w

a r e R A I D

1. Direct-attach

F i l e

/ r e c o r d

l a y e r

B l o c k

l a y e r

NAS

server

4. NAS server Host

3. NAS head

NAS

head

Host

LAN

H o s t . w

i t h L V M

Disk array

SN

2. SN-attach Application

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Uses for the model

Vendors place products in the space of architectures

clarify product differences

Customers understand vendor offerings better

The industry

basis for common definitions, communication,understanding, interoperability

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Conclusions

The SNIA shared storage model is both simple anduseful to highlight similarities and differences

as a basis for comparisons Still a work in progress

data movers, tape drives, …

better comparisons …

suggestions?

The SNIA-TC welcomes input: <[email protected]>

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Authors

John Wilkes, Hewlett-Packard (project lead)

Harald Skardal, NetApps

David Black, EMC

Wayne Rickard (SNIA TC chairperson), Gadzoox

Co-conspirators: the rest of the SNIA TechnicalCouncil Dave Anderson, Seagate Technology

Jim Carlson, IBM Garth Gibson, CMU/Panasas

Kevin Phaup, HighGround Systems

David Thiel, Compaq

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