Nas fundamentals

Advanced Technical Support, Americas
© 2012 IBM Corporation
Network Attached Storage
The Basics
Norman Bogard

Agenda
 Origins of Network Attached Storage
 Terminology
 Data Transfer: Block versus File
 Converged Storage
 NAS Techniques
 Additional Resources
 A note of thanks for input from
– Brett Cooper
– Nils Haustein
2

Origins of Network Attached Storage (NAS)
 Ethernet was invented in 1973
– By Robert Metcalfe of Xerox
– First paper on Ethernet didn’t come until 1976
 In the early 1980’s Newcastle University demonstrated remote
file access with UNIX systems
 In 1983 Novell’s NetWare Core Protocol (NCP) was released
 In 1983 Barry Feigenbaum of IBM invented Server Message
Block (SMB)
– Foundation of the Common Internet File System (CIFS) {1996}
 In 1984 Sun Microsystems released the Network File System
(NFS)
 The 1990’s saw the beginning of dedicated NAS devices
3

Origins of NAS Continued
 By late 1991 the HyperText Transfer Protocol (HTTP) &
Hypertext Markup Language (HTML) were defined
– HTTP is now often referred to as Representational State
Transfer (REST)
• REST is the foundation of cloud based storage services like
Amazon’s S3
 NAS is always Client / Server based
– Appliance (file server) is the server
– End systems, like workstations or application servers, are the
clients
 1992 saw the beginning of Samba
– Samba gets it’s name from SMB & grep -i '^s.*m.*b'
– Samba integrates NFS & CIFS so files can be shared by both
4

Terminology
 Block: Leverages Small Computer System Interface (SCSI) commands to
read-write specific blocks
– Common SCSI access methods include Fiber Channel (FC), Internet Small
Computer System Interface (iSCSI), or InfiniBand (IB)
• IB is a high speed network interconnect
 NAS: reads/writes files
 File Server: A storage server dedicated (primarily) to serving file-based
workloads
 NAS Gateway: A server that provides network-based storage virtualization
– Provides protocol translation from host-based CIFS/NFS to Storage Area
Network (SAN) based block
– Examples: IBM N series & SONAS; NetApp V Series; EMC VNX/Celerra;
OnStor (LSI); HP P4000 Unified Gateway
 Unified Storage – a single logical, centrally managed storage platform that
serves both block (FC, iSCSI, IB) and file-based (CIFS, NFS, HTTP, etc.)
workloads
– Examples: IBM N series; NetApp V series; & IBM Storwize V7000 Unified
5

Comparing SAN & NAS
6
* Internet Protocol / User Datagram Protocol
*

Block vs File
7
Block Level Storage devices / SAN
(i.e. V7000, DS8000, XIV)
● Provide access to equal sized blocks of storage
● Blocks are found by a number on a device
● Read and Write operations on data blocks –
mainly SCSI protocol
● Block Services segmented into LUNs or vDisks –
usually a few dozen
● Connections to the device in the order of 10-100
● Authorization for generic access by host (10-100)
● Almost no coordination of concurrent access to
these LUNs (other than SCSI protocol device
reservation)
NAS devices
(i.e. N series, SONAS, or V7kU)
● Provide access to files
● Files are found by a name within a tree of names
● Read, Write, Create, Delete and many more –
CIFS, NFS, FTP and other protocols
● Device Services exposed as Exports, Directories,
Files – a few hundred, millions, billions
● Connections can be in the order of 100-10.000s
● Authorization by User ID – for Reads, Writes, Meta-Data operations
● Coordination of concurrent access with Share
Modes and leases/delegations (on whole files),
byte range locks (fragments within files) –
within a protocol (ie CIFS) and across protocols
(i.e. between CIFS and NFS)

Data Transfer: Block versus File
 The key to understanding the difference between
block and file data is the file system owner
8
STORAGE
APPLICATION
Storage Area Network
(SAN)
FC, iSCSI, or IB
NETWORK
FILE SYSTEM
STORAGE
APPLICATION
FILE SYSTEM
Direct Attached Storage
(DAS)
STORAGE
NETWORK
APPLICATION
FILE SYSTEM
Network Attached Storage
(NAS)
IP: CIFS, NFS, Etc.

Converged Storage (Unified Storage)
 Two fundamental approaches to intermixing block &
file storage within a single system
– IBM’s N series uses block on file
• A device file with a Logical Unit Number (LUN) assigned to it
is stored within the file server’s Write Anywhere File Layout
(WAFL) file system and then mapped to a host
• File & block data are stored within the same file system
– IBM’s Storwize V7000 Unified (V7kU) uses file on block
• A raw device from the V7k is mapped to hosts
• File data is contained within discrete devices
• Host block data is contained within discrete devices
• File & block data are stored independently
9

10
Internal
Disks
Mapped LUN = File File Share
File Server
(WAFL File System)
Internal
Disks
SAN
Block-on-File
(N series)
File-on-Block
(V7kU)
FC, iSCSI CIFS, NFS
File Modules
(GPFS)
V7kU
Block Devices
FC, iSCSI Mapped LUN CIFS, NFS
SAN

Block vs File – High Level Application Affinity
 Applications/data types that typically reside in block stores:
– RDBMS (Oracle, SQL Server, DB2)
– Analytics (stream processing)
– OLTP
– Metadata Layers (component of content management)
– Email (MS Exchange, Notes)
– Virtualization Stacks (VMware: VDI, VMDK implementations; HyperV; Citrix Xen)
 Applications/data types that typically reside in files:
– Rich Media (pictures, videos, seismic data, medical imaging, etc.)
– VOD, AOD, IPTV
– Analytics (SAS grid)
– ECM (Enterprise Content Management – e.g., web stores)
– Research Data Sets
– User files (documents, etc.)
– PLM/PDM (Product Lifecycle/Data Management)
– Virtualized Environments (VMware client-driven deployment)
11

The Enterprise Workload Landscape… What Fits Where?
Application Workload Class
LEAD
WITH
Comments
Oracle DBMS B (F) For larger (>20TB) instances, lead with XIV
eBusiness Suite B (F)
SAP OLTP B OLTP/BASIS
BWH F (B) Analytics
Content Mgt.
Filenet, Documentum,
etc. F Metadata layer may be block/RDBMS
Media Streaming VOD, AOD, IPTV F Very performance/latency sensitive; also potential for tape/LTFS
MS Exchange 2010 B Strong ESRP results for both V7K & XIV
2003/2007 B
Lotus Notes B (F) Back end is DB2 database; predominantly block
VMware Virt. Infrastructure B (F) Block: mature (also XIV); File: emerging (MS HyperV – block only)
VDI B / F
IBM DB2 RDBMS B
SAS Analytics B / F Block: mid-range, File: grid; XIV certified & strong; V7KU TBD
PACS/EMR Imaging F Ex.: Cachet Database
Prod. Workflow B / F “Front Office” OLTP: block; Patient archives: file
B: Block; F: File
12

Data Protection: File vs Block - Concept
STORAGE
NETWORK
APPLICATION
FILE SYSTEM
STORAGE
APPLICATION
NAS
(Network Attached Storage)
SAN
(Storage Area Network)
NETWORK
FILE SYSTEM
• Generally
snapshots are
consistent
since the file
system is
consistent on
the NAS System
• Replication is
supported
• NDMP is
leverages
snapshots and
dumps files to
tape
• Integrated
with most
leading
backup
software
• Snapshots
require
integration with
the host file
system and
application to
ensure
consistency
• Backups are
done by moving
blocks through
a master-media
server to
disk/tape
• Replication is
supported once
file system is
consistent
• Acts just like
Direct Attached
Storage
13

Integration points for NAS protocols with
applications
 NAS applications historically have required very little if any
integration with host applications
– Many NAS vendors now provide Application Programming Interfaces (APIs) to
integrated with leading host applications such as Vmware
• Provides seamless movement and recovery of virtual machines through replication
 Many third party management solutions support NAS integration to
discover and manage the storage, including our own Tivoli
Productivity Center (TPC)
 Microsoft Windows Server Applications such as Microsoft
Exchange Server and Microsoft SQL Server do not support NAS
shares for data placement
– These applications require block storage
14

NAS Techniques overview
 File systems
 File shares
 Network services
 Authentication and authorization
 Quota
 Data availability
 Date protection (snapshot, backup, NDMP,
replication)
 Anti virus support
 Information Lifecycle Management
 File cloning
15

File systems and file-sets
 File shares are exports to the user or
application
 User files are organized and stored in file
systems
– File system is local to the NAS system
 File-sets allow for breaking down the file
system space in smaller manageable
units
– Certain operations can be configured for
file-sets such as replication, snapshots,
and quota-management
 Pools allow placement and migration of
files to different cost storage devices
16
NAS System
File-set
(optional)
File System
Pool
(optional)
Share
NFS, CIFS, HTTP, FTP, …
Share
Storage Storage
Pool
(optional)
Pool
(optional)
File-set
(optional)
File-set
(optional)

File shares
 File share is a user file system provided by the file server
– Allow users and groups to share files in a common name space
– Access permissions can be given based on user and group
names
 Typical file sharing protocols are CIFS and NFS
17
 CIFS share is exported under share-
name (usershare) which is mounted by
the user
 NFS share is exported as directory
(/shares/nfs) which is mounted by the
user (as mnt/userdata)
CIFS
Directory: /shares/cifs
Sharename: usershare
Mounted as CIFS share:
filerusershare
File Server
Share
NFS
Directory: /shares/nfs
Mounted as NFS share:
Filer:/shares/nfs /mnt/userdata
File Server
Share

File shares and TCP/IP address failover
 NFS is state-less
– Upon TCP/IP address failover NFS client experiences a short interruption
– I/O continues when TCP/IP connection is available, no re-connection required
• Even though NFS v4 is state-full, durable file handles eliminate the need for a re-
connection
 CIFS is state-full
– Upon TCP/IP address failover CIFS client looses connection
– File share must be reconnected (mounted) before I/O can continue
– Additional tools can be used to automate reconnection (e.g. DFS)
18
Clustered File Server with two file modules
NFS Client connected to module 2 CIFS client
Module 2:
10.10.10.2
Module 1:
10.10.10.1 X
10.10.10.2
Requires reconnect!
I/O continues

Network services
 Network Time Protocol (NTP) is used to synchronize the time
between components (File Server, directory server)
– Very important for authentication services with kerberos and clustered
NAS
 Domain Name Service (DNS) is used to resolve names and IP
addresses
– Required for active directory authentication
– DNS round robin can be used for load balancing
 DNS round robin sequentially selects IP addresses
19
File Server.storage.com
Client 1 Client 2 DNS server
File Server.storage.com
10.10.10.1
10.10.10.2
10.10.10.3
10.10.10.4
Module 2:
10.10.10.2
10.10.10.4
Module 1:
10.10.10.1
10.10.10.3

Multipathing Solutions for NAS
 Link Aggregation
– Relies on the Transmission Control Protocol/Internet Protocol
(TCP/IP) level integration
• Handled at either the switch port level or at the network layer of the Open
Systems Interconnection (OSI) model
– OSI layer 3
– Commonly Known As: Bonding, Teaming or Trunking
 Logically bonds multiple network paths into a single path
effectively increasing the bandwidth and providing redundant
physical connections in the case of a failure
 Uses round-robin scheduling, or is based on hash values
computed from fields in the packet header, or a combination
of these two methods
– Network load is balanced across all links unless active/passive
mode is chosen
1 GbE
1 GbE
1 GbE
1 GbE
2 GbE
2 GbE
20

Authentication
 Authentication validates a resource – whether it is who it claims to be
– A resource can be a computer, user, or group
 Authentication can be done local within the file server
– Local authentication of users requires the user to be configured in the file
server
• This does not scale is not manageable because every user must be configured in
every file server
• Only works in small environments
21
 Authentication can be done remote with a
directory server
– Directory server contains names, profile information,
and machine addresses of every user and resource
on the network
• It is used to manage user accounts and network
permissions
– Upon user access the file server validates user
credentials with the directory server
– Directory servers are Active Directory, LDAP, etc.
NAS file server
User
Directory
server
1. Connect
with
credentials
3. Grant
access
2.Validate
user

Authentication processing
22
Clients
w/o Kerberos
file server
Authentication
Server
with
Kerberos
KDC
1. User Auth. Request
4. Response
2. verify Auth. Request
3. Response
Clients
with Kerberos
1. User Auth. Request
2. Granted Kerberos Ticket
3. Kerberos Ticket
4. Response

Authentication by protocol
 Authentication for NFS is based on host names or IP addresses
– Allowed host-names are typically configured on a per-share basis
– Network Information Service (NIS) can be used to group host-names
• Allows single point of maintenance for host-groups
– NFS also supports user authentication via Kerberos
 Authentication for CIFS is based on Security Identification (SID)
– Each resource within a domain has a unique SID
– SIDs are known to the directory server
– Authentication process validates SID with directory server
23
Client
Directory
Server

 Authorization validates access permissions of user/group to directories/files
– Each shared file and directory has access permission
 Access permissions are also called Access Control Lists (ACL)
– In Unix (NFS) access permissions are simple: r-w-x for owner, group, others
– In Windows the ACLs are more complex
•One user can be in multiple groups
•ACLs include change, append and attribute operation permissions
Authorization
Name ACL Owner Group
Myfile.txt rwx r-- --- MIA root
24
Share
User: MIA
Group: Users
 Upon file access the file server matches user credentials
against file-ACL and validates the level of access for the
user
– ACLs can be inherited from parent folders
 Authorization takes place after authentication

Quota
 Quotas are used to restrict certain aspects of the file system
(share) usage:
– Capacity
– Number of files
 Set by the administrator for specific user, group, file system, or file-
set
 Hard-quota: when reached writing files is denied
 Soft-quota: user or administrator may get a warning, but can
continue to store files
– Grace period may start during which the user can continue to store
files
– When a hard-quota is reached, the user cannot store anymore files
25

Data availability techniques
26
Disk System
(RAID)
File system
(Replication, striping)
Replication, Data striping
Storage network
(Redundancy)
Redundant storage networks
RAID protection on disk subsystem
NAS services
(cluster)
Clustered NAS services
NAS Protocol
NAS System

Data protection
Against what must the data be protected ?
 Techniques to protect against operational errors (changes,
deletion, virus)
– Snapshots
– Backup
 Techniques to protect against disaster (complete failure of
computer center)
– Replication / Mirroring
– Backup
27

Snapshots
 Snapshots freeze the state of a file system or subset at a
certain point in time
– Data resides in the same file server
 Snapshots are typically space efficient
– At the time of the snapshot almost no capacity is consumed
– Changes in the file system cause snapshots to grow
 Snapshot management
– Snapshots can be scheduled by date and time
– Snapshots can be deleted automatically based on rules
 Snapshots can be mounted and accessed by users
– Read-only, no changes allowed
 Snapshot are used to recover deleted or changed files
 Also used for other background operations (backup,
replication, etc.)
28
Snap
File system Snapshot

Backup and Recovery Techniques
Backup from shares Integration in file server
Backup client runs on every user
workstation or on dedicated server(s)
–Backs up the files in the file system
 Dedicated servers provide more
scalability
Recovery can be done by the backup
client
–Can be done by user
General concern: long file scan time
Backup clients run on file server
–Backs up files from file systems
Leverage fast scan process
Recovery can be done by the backup
client internally to the file server
–Usually administrative effort
29
User Dedicated
Backup client(s)
Backup
Server
BR client
BR client
Share
File Server
User
Backup
Server
Share
BR client
File Server

Backup & Recovery considerations
 Typically full, differential and incremental backups are supported
– Full: entire file system or share
– Differential: all changes since last full backup
– Incremental: all changes since last full or differential backup
 Typical requirements
– Backup window: depends on number of files and speed of identification process
– Recovery time: depends on number of files to be recovered and backup medium
– Recovery point: depends on frequency of backups
 Scalability of backup and recovery depends on:
– Number of parallel backup clients
– Network and storage medium
– Scan time
 Use file level backup to recover files or subset of files
 Full system recovery (disaster) may take a long time because restore is typically
on a file level
– Consider other techniques for disaster recovery (replication, etc.)
30

Network Data Management Protocol
31
file server
NDMP Client
NDMP
Backup
Server
(Source: „Storage networks explained“,
Troppens et al, John Wiley & Sons, Ltd, 2009)
 Standardized protocol facilitating backup and recovery for NAS server
 Comprises three services:
– Data service: performs the backup and recovery operation in the NAS server
– Tape service: writes and reads data to the backup storage medium (disk or
tape)
– Data management service (DMA): controls backup and restore operations and
NDMP data movement

NDMP Backup Functions
 Files are backed up in NDMP data stream to tape service
– Streaming provides higher performance
– Meta information is passed to DMA
 NDMP supports full and incremental backup for file systems
 NDMP supports file system and file level recovery
– File system recovery is fast because of streaming
– File level recovery is based on “direct access recovery” where the
NDMP client keeps track of position of file within NDMP data stream
 NDMP version 5 supports compression, encryption and
multiplexing
 Recovery of entire file systems is faster than with file-level backup
– Instead of single files entire container of files (streams) are recovered
32

NDMP for data migration (copy)
 NDMP can be used for data migration (copy) between file servers
– One file server is the source and runs the data service (DS)
– Another file server is the target and runs the tape service (TS) and data service
– DMA runs externally or on either of the file servers
 Source file server (DS) collects the files and attributes and streams it to
target file server TS
 Target file server receives (TS) the stream and DS unpacks it
 General issue: data format within the NDMP stream is not standardized
33
Source file server Target file server
DS
TS
DS
DMA
Data stream
NDMP Control

Replication / Mirroring
 Copy files from one NAS system to another for disaster protection
 Copy can be done on storage system or file system layer
– File system replication typically allows faster recovery (fail over)
– File system replication is more consistent because it has the
awareness of files
– Storage system replication is typically faster and can also be fully
synchronous on block level
 Typically asynchronous methods are used in a NAS environment
 Multi-side and multi-directional replication scenarios are possible
34
Site 2 Site 3
Site 1

Replication considerations
 Data reduction techniques (compression, de-duplication)
help to overcome replication bandwidth challenges
 Encryption helps to provide secure data transmission
between sites
 Main requirements for disaster recovery
– Recovery time objective: how long does it take to recover from
a disaster
– Recovery point objective: how much data will be lost
 Recovery process typically involves administrative
measures at the target site
– Should be well documented and trained
35

Virus protection
Scanning on file shares Scanner integration
with file server
Scanner in file server
Scanner running on user
workstation has limited
scalability
Dedicated scanner(s) are
more scalable
–Need access to shares
File identification may
become the bottleneck
Leverage integrated file
identification techniques
for bulk file scan
Enables scan on-
demand
–On file access
–After file write
Scales with number of
scanners
Scanner runs in file
server
Leverages integrated file
identification techniques
for bulk file scan
Enables scan on-demand
–On file access
–After file write
Limited scalability and
scanner support
36
User Scan Server(s)
Scanner Scanner
Shares
User
Shares
Scanners
User
Scan Servers
Shares
Scanners
AV
Agent

Tiered storage
 Important Information Lifecycle Management technique
– Initial placement of files on the most appropriate storage medium
– Policy based migration during the lifetime of the files
– Keep the files in the original name space to allow transparent access
 Supports the idea of archiving
– For data at rest which needs to be kept for long periods of time
 Integration of ILM functions in file server provides cost efficiency
– No extra infrastructure required
– Central administration in concert with other functions
37
Automated tiering
file server
Gold Silver Bronce Tape
Performance and Cost

Scale out
 Scale out NAS systems can scale in multiple dimensions
– Horizontally: performance and throughput provided by interface nodes
– Vertically: storage capacity provided by storage systems
 Provide single name-space across multiple processing nodes (interfaces)
 Workload is distributed across the components (interface and storage
nodes)
 Centrally managed and maintained
38
Interface nodes
Storage systems
Performance
Capacity
One global namespace

Traditional NAS vs. Scale Out NAS
39
 Scale performance and capacity with number of
disks and file servers
 Adding file servers leads to fragmented data, hot
spots and underutilized disks
 More complex to manage multiple NAS appliances
 Operational costs grow
ALL FILES
“Scale Out NAS”
Goal of Scale Out NAS:
A few “traditional NAS” challenges:
“Traditional NAS”
file
server
1
File 3
File 2
File 1
Storage
Island
file
server
2
Storage
Island
file
server
3
Storage
Island
Single large ‘virtual’ server
including automated storage tiering
Cluster
Interface
node 1
Interface
node 2
Interface
node 3
Interface
node n
 Scale performance and capacity
independently
– With interface and storage nodes
 Very high aggregate performance through
parallelism
 Greatly simplified management because it
is one system
 Provides operational cost reduction

Multi-tenancy
 Provide file space for multiple tenants
 Example
– Multiple departments / organization in one company
– Multiple customers hosted by service provider
 Requirements
– Separation of networks
– Separation of interface nodes
– Separation of storage
– Separation of administration
– Separation of authentication
– Different protection concepts
– Reporting and chargeback, etc…
 Simple Solution: provide one file server per tenant
– Complex to administrate and to maintain
– More costly due to underutilized disk space and complexity
 Combine multi-tenancy with scale-out NAS
40
User Dept. Client
Backup
Authentication
Antivirus

Multi-tenancy and scale-out
 Scale-out system provides scalability in multiple dimensions
 Scale-out system allows dynamic allocation and de-
allocation of resources
 Scale-out system can be centrally managed and maintained
 Scale-out systems help save cost in a multi-tenant
environment
41
Interface nodes
Storage systems
Namespaces
User Dept. Client
Scale-out Systems
Backup
Authentication
Antivirus

File cloning
 Clone is a writable space efficient copy of an individual file
– Clones ‘point’ back to the parent file
– Only modified blocks from clone are stored
 Parent file is read-only, cannot be modified as long as a clone exists
 Multiple clones of the same file can exist
– Clones of clones are possible as well
 Clones can only be created within the file server
 Use case: Provision virtual machines from the same base image
42
Parent file
(read-only)
Writeable
clone files
Source file

Additional Resources for more information on NAS
 Wikipedia’s Definition of NAS:
– http://en.wikipedia.org/wiki/Network-attached_storage
 InfoStor: NAS Advantages a VARs View:
– http://www.infostor.com/index/articles/display/55961/articles/infostor/volume-2/issue-
4/news-analysis-trends/nas-advantages-a-vars-view.html
 About.com: SAN vs. NAS: What’s the difference?
– http://compnetworking.about.com/od/networkstorage/f/san-vs-nas.htm
 About.com: Introduction to NAS – Network Attached Storage
– http://compnetworking.about.com/od/itinformationtechnology/l/aa070101a.htm
 FreeBSD Handbook: What is NFS?
– http://www.freebsd.org/doc/handbook/network-nfs.html
 CodeFX: CIFS Explained
– http://www.codefx.com/CIFS_Explained.htm
 Wikipedia’s Definition of Samba:
– http://en.wikipedia.org/wiki/Samba_%28software%29
 SearchStorage: Using NAS NFS with VMware ESX Technology Pro’s and Con’s
– http://searchstorage.techtarget.com/tip/Pros-and-cons-of-using-NAS-NFS-with-VMware
– (Requires Account Creation to view)
43

Question and Answer

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MHz / GHz only measures microprocessor internal clock speed; many factors may affect application performance. When
referring to storage capacity, GB stands for one billion bytes; accessible capacity may be less. Maximum internal hard
disk drive capacities assume the replacement of any standard hard disk drives and the population of all hard disk drive
bays with the largest currently supported drives available from IBM.
IBM Information and Trademarks
The following terms are trademarks or registered trademarks of the IBM Corporation in the United States or other
countries or both: the e-business logo, IBM, System Storage, Easy Tier, FlashCopy, and System Storage DS.
Linear Tape-Open, LTO, the LTO Logo, Ultrium, and the Ultrium logo are trademarks of HP, IBM Corp. and Quantum in the
U.S. and other countries.
Intel, Pentium 4 and Xeon are trademarks or registered trademarks of Intel Corporation. Microsoft Windows is a
trademark or registered trademark of Microsoft Corporation. Linux is a registered trademark of Linus Torvalds. Other
company, product, and service names may be trademarks or service marks of others.
47

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