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NAS and GatewaysConsiderations for File

Storage

Randy Kerns Copyright © 2003 - All Rights Reserved

Evaluator Group, Inc.

7720 E. Belleview Avenue • Suite 210 • Greenwood Village, CO 80111(303) 221-7867 • Fax: (303) 221-1615

www.evaluatorgroup.com

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Agenda

Structure of I/O

File Storage

Applications – file vs. block

NAS storage• Structure

• NAS Gateways

• Considerations

• Evaluation

NAS Management

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Structure of I/O

All Open Systems use a similar I/O method• minor variations

• some terminology differences

• includes all flavors of Unix

• includes NT/2000/XP/2003 Server

Structure is for a “Layered I/O”• elements in each layer has different capability

• layers may come from different vendors

• system may contain different elements at each layer depending on

device or usage

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Layered I/O StructureApplication /

Database

Operating System

File System

Device Driver

Interface Hardw are

Device

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File StorageFile System

• file and directory structure on logical disk (typically single)

• contains metadata to describe information (size, location, dates, etc.) on the disk. Ex: superblock, inode

• different types of file systems with different methods of access

• file system handled by software in program stack of operating system

• multiple file systems may be present at one time

• “mounted” file systems or “shares” are remote file systems

dev bin etc usr

/

aps test

passwd hosts

Mountedfile system

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File Systems VFS Virtual File System FFS Fast File System UFS UNIX File System – used interchangeably with FFS AFS Andrew File System – also Distributed File System NFS Network File System – developed by Sun RFS Remote File System – developed by AT&T S5FS Original System V file system VxFS Veritas Journaling File System JFS Journaled File System – AIX CFS Cluster file system – Tru64 EXT2/EXT3 2nd/3rd Extended File System – Linux systems GFS Global File System – Linux ReiserFS Journaling file system – Linux XFS Extended File System – SGI and others CXFS Clustered Extended File System – SGI QFS 64-bit very large file system – Sun Solaris HFS Hierarchical File System – S/390 UNIX NTFS Windows NT/2000/2003 FATxx Windows – several versions

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ApplicationsMay be written to do file I/O or block I/O

• File I/O

Uses the file system driver

Caching done by system

Typically system utilities for management

I/O done to FILE HANDLE: Offset

• Block I/O

Used to bypass file system – performance reasons

and overhead in capacity

Buffering/caching done by application (ie database)

Called RAW I/O

I/O typically done to blocks – linear address space

Special utilities for management

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Network Attached Storage

Disk array

Workstation Workstation Tower boxHost

LAN

Server

Storage

I/O Requests forfor File I/O using

NFS, CIFS

Server owns storagedevice and does block

level I/O

NAS

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NAS I/O Structure

LAN

Client Computer System

Application

File I/O Access

I/O Redirector

Network File Protocol(NFS, CIFS)

TCP/IP Stack

NIC Driver

Ope

ratin

g S

yste

m

Network Interface Card

Remote File I/OAccess Across

the Network

NetworkFile

Protocol(NFS,CIFS)

TCP/IPStack

NICDriver

NAS File Access Handler

NAS Device

File I/O

Disk System

FileSystem

VolumeManager

DiskSystemDeviceDriver

DiskController/

HBA

Block I/O

Ope

ratin

g S

yste

m

NetworkInterface

Card

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NAS GatewaysThe controller function of

NAS with the storage decoupled• Connected to a SAN – fibre channel

typically• May be separate product or a

version of a standard NAS product• can utilize SAN capabilities • does introduce a different

management scheme – adds the SAN storage management as well as the NAS administration

Application

Rem oteFile System

DiskSystem

Netw ork Attached Storage w ith SAN Storage

Com puterSystem

Local Area Netw ork

FileRedirector

NAS Device

SAN

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NAS Gateways

Typical usage profile• Enterprise data center environments with existing SAN

Requirement for file storage

Consolidation of existing, independent NAS devices

Centralized administration and purchasing

Storage system partitioned for NAS filesystems

(LUNs)

• Administration cost

Target is to reduce overall storage administration

costs

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NAS ConsiderationsFIRST: What are your requirements?

• Part of overall storage strategy Future needs Timeframe for deployment Cost structures

• Understand needs for users, applications, business Does application require file or block access?

What environment will it used in?• Enterprise data center

• Small to Mid-Size Business (SMB)

• Departmental

• Workgroup

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NAS ConsiderationsWho will administer

• Dictates tools and capabilities• Organizational tension

Usage considerations• Protocols – CIFS, NFS, HTTP, FTP, NCP• Data sharing – locking requirements• Connectivity – number and type of connections• Security – IP/Ethernet usage, data at rest• Performance

Types of data - bandwidth or response time sensitive

• OLTP• Large Block – video, etc.

Responsiveness – guarantees, application requirements

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NAS ConsiderationsAdvanced services

• Part of consideration

• Requirements dictate which are of concern

Remote copy for disaster tolerance: Technology used,

distance, cost, currency of data, recovery process, time

to recovery

Point-in-Time copy functions: Local and remote, capacity

consumed, ability to restore versions, make available

read/write

Backup: LAN-free, use of SAN devices, NDMP support,

favorite backup software usage

Management: incorporation into overall storage

management strategy, aggregation

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NAS Considerations

Capacity required• Today and tomorrow

• Scaling issues

Additional NAS devices vs. additional disks

Performance scaling

Management

Is a NAS Gateway the best option ?• Usually environment specific

Enterprise data center with existing SAN

Storage professionals managing storage

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NAS Evaluation

Develop a set of criteria• Put in elements that are part of your requirements

• Give little weight to extraneous items (So What?)

Evaluator Group workbook• As example

• EG_NAS_Workbook.pdf

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Evolution• NAS devices each individually managed

Installed and administered as unique devices

• Management does not scale

Additive costs for additional NAS devices

• Few sophisticated tools

Expectation for capacity planning, performance

monitoring and reporting, and SLA adherence didn’t

exist

• Changes are underway for NAS management

NAS Management

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Aggregation• Management software to manage multiple NAS devices

• Two methods

Individual devices with information accumulated

• Statistics, capacity information

• Controls, status

Multiple devices managed as single entity

• Dynamic allocation of capacity – adding of capacity

(units)

• Data protection dynamically spread among devices

• Performance tuning by distributing data

NAS Management

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NAS Aggregation Example• Software to collect information

about NAS appliances Same vendor

• Unified view to monitor and control

Status and events Capacity Appliances, OS versions Volumes Disk devices

• Addresses admin costs in homogeneous environment

Servers

NAS Management

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NAS Aggregation

Example• Data accessed as if single NAS

appliance – NAS array

• For increased capacity, add

appliances

• Data is redistributed across

appliances

• Clients see additional capacity

with no required changes

• Management as a single entity

Servers

NAS Appliances

NAS Management

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Summary• NAS Management is maturing

• Economics of management / administration cost is now

becoming important

Necessary with expanded use of NAS

Capacity growth accentuate the problem

• Need to integrate with SRM tools

Must include NAS devices from different vendors

Still a long way to go to have enterprise tools

NAS Management

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NAS Summary

Choice of NAS is an easy answer in some

environments• Traditional NAS usage in departmental and workgroups

• More difficult in enterprise data center environments

Where the requirements are understood and the

attributes of NAS answer them

Where the overall storage strategy can incorporate

NAS into existing environment

• Includes management tools

• Infrastructure

• Costs – separate IP network, NIC changes

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