Accelerating the Performance of Centrally Managed File Services

Solution Sheet

Overcoming the WAN

Limitations of CIFS, NFS,

FTP, and Xcopy

Accelerating the Performance

of Centrally Managed File Services

It is a challenge to maintain synchronized

les across a distributed enterprise. In

addition, it can be costly to deploy and

manage le servers in remote and branch

ofces. As a result, most enterprises prefer

to centralize enterprise le servers.

However, inherent limitations exist in

existing protocols, le sharing applications,

and WAN technologies that make it difcult

to provide le services across a WAN.

This is true across most le sharing

technologies, which include:

• The Common Internet File System

(CIFS) protocol, which is used by

Microsoft

le systems. CIFS is a

particularly “chatty” protocol, which

limits its performance across networks

with high latency. Every time a le is

transferred using CIFS, for example, it

is methodically broken down into small

blocks (4 KB to 64 KB). Each block

is sent individually by the le server,

requiring an acknowledgement by the

client before the next set of information

can be transferred. This often results in

signicant latency across a WAN.

In addition, because CIFS uses TCP as a

transport protocol, it is subject to normal

TCP back-off procedures during periods

of congestion. This often adds even

more latency across the WAN, further

debilitating application performance in

many enterprise networks.

• Network File System (NFS), a

common le sharing application used

by UNIX le systems. Unlike Microsoft

CIFS, the underlying NFS protocol can

use either UDP or TCP as a transport

mechanism. Therefore, it does not suffer

from performance limitations that come

with TCP backoff. However, NFS is a

relatively chatty protocol, which makes it

difcult to deliver this application across a

Wide Area Network (WAN).

• File copy utilities, like FTP and Xcopy,

are used to batch copy or transfer les

between multiple locations, often as part

of regular backup or disaster recovery

programs. XCopy operates on top of the

Microsoft CIFS protocol, and therefore

suffers from the same limitations as

other CIFS applications. FTP, on the

other hand, does not rely on a chatty

protocol, like CIFS. However, because

it operates over TCP, it is still limited by

the bandwidth and latency constraints of

many enterprise WANs.

When limited bandwidth is coupled with

high latency (100ms or greater), packet

loss, and TCP delays, as is the case on many

enterprise WANs, it becomes difcult to

deliver le services effectively. Fortunately,

Silver Peak is able to overcome the

limitations present in most le applications

through protocol acceleration, compression,

and advanced data reduction techniques.

Data Reduction Using

Network Memory

Silver Peak appliances use Network

Memory

™

to reduce the amount of

repetitive information that is sent across

the WAN when performing le access and

storage. Depending upon the type of le

being transferred, this can lead to enormous

performance improvements — 60x in some

instances (see Figure 1).

Silver Peak’s Network Memory is

bidirectional. Once content traverses a

WAN in one direction, the patterns are

stored in each appliance. Future transfers

in the opposite direction are immediately

accelerated, enabling Silver Peak to offer

amazing performance with exceptional

scalability. As Figures 2 and 3 show, this

capability provides signicant benet

across different methods of le transfers.

Solution Sheet

Network Memory operates at the network

layer of the OSI stack. As a result, unlike

other application acceleration appliances,

Silver Peak is able to accelerate the

performance of ALL le sharing applications

using data reduction, including those

that use UDP, such as NFS. The result

is a signicant improvement in NFS

performance (see Figure 4 below).

Compression and Protocol

Acceleration

In Figures 1 and 2, the Silver Peak solution

demonstrates performance improvements

on initial le transfers — prior to data

being stored in the appliances. This is

due to crossow payload and header

compression, as well as various techniques

for TCP acceleration, including window and

transaction size adjustments to compensate

for poor performance on high latency links.

CIFS Performance Improvement (client-to-server)

10x

15x

20x

25x

30x

35x

40x

45x

50x

55x

1 Mb .xls 2 Mb .doc 1.8 Mb .jpg 6.1 Mb .ppt

Silver Peak (1st transfer)

Silver Peak (2nd transfer)

CIFS Performance Improvement (server-to-client)

10x

15x

20x

25x

30x

35x

40x

45x

50x

1 Mb .xls 2 Mb .doc 1.8 Mb .jpg 6.1 Mb .ppt

Silver Peak (1st transfer)

Silver Peak (2nd transfer)

Figure 1.

Figure 2.

Figures 1 and 2: CIFS Performance improvements on both

directions of a 1 Mb link with 100 ms latency and 0.05% loss.

Solution Sheet

Silver Peak also supports CIFS acceleration,

including read-aheads and write-behinds to

pipeline CIFS requests and the respective

acknowledgements. This dramatically

minimizes roundtrip delays in Microsoft

le sharing environments.

Comparison To File Caching (“Wafs”)

Wide-Area File Systems (WAFS) emerged

in the last few years as a way of improving

data access delays inherent in traditional

remote le protocols. This solution

leverages caching technology to enable

the consolidation of enterprise data,

coupled with specic protocol acceleration

techniques to improve le access and

storage across the WAN.

While le services are essential to

enterprise operations, and should be a

fundamental component of any application

acceleration solution, enterprises have

balked at the notion of deploying a

dedicated point solution based heavily on

caching, as is the case with WAFS.

Following are the main challenges associated

with using a le caching solution, such as

Figure 3.

Figure 4.

Figure 4: Network Memory works at the network layer, providing

signicant performance improvements across all TCP and UDP

applications, including NFS.

Figure 3: Network Memory is bidirectional, providing dramatic performance

improvements in both directions of a le transfer.

Performance Improvements - FTP Transfer

(Uncompressed VMware system image)

10x

20x

30x

40x

50x

60x

Server-to-Client Client-to-Server

1st transfer (server-to-client)

2nd transfer (server-to-client)

1st transfer (client-to-server)

2nd transfer (client-to-server)

NFS (over UDP) Performance Improvement

1 Mb .xls 2 Mb .doc 1.8 Mb .jpg

Document Type

Improvement

Silver Peak (1st transfer)

Silver Peak (2nd transfer)

888.598.7325 | www.silver-peak.com

and are used to identify, products or services of their respective owners.

Solution Sheet

WAFS. By integrating le services as part

of a complete application delivery system,

these issues are easily overcome with Silver

Peak NX Series appliances:

• Application Transparency. WAFS are

application-specic point products that

only optimize le services. In contrast,

Silver Peak accelerates all business critical

applications, such as web, email, disaster

recovery, streaming video, and VoIP, in

addition to le services. Supporting a

wider breadth of applications ensures a

faster return on investment.

• Data coherency. WAFS products act

as a proxy, delivering cached copies of

original content. They are therefore

subject to coherency issues when

multiple people are accessing the same

information. Local Instance Networking,

on the other hand, does not alter client/

server communications (Figure 5). NX

appliances inspect trafc in real-time,

delivering exactly the same information

that is being served by the host itself.

• Seamless Integration. Most WAFS

products require client PCs to be

recongured, which can be a signicant

burden to IT staff. Local Instance

Networking does not require any

reconguration of clients, servers, or

applications, facilitating deployment and

management.

• Security, compliance, and

management. Despite storing sensitive

business information, many WAFS

products do not use data encryption to

protect local data stores. In addition,

WAFS appliances require a full set of

access control mechanisms to replicate

the security features of le servers.

This means that IT organizations are

replacing actual le servers with less

secure devices that require just as

much day-to-day management.

The Right Solution for Centralized

File Services

Silver Peak is an indispensable solution

for enterprises delivering le services to

remote and branch ofces via centralized

servers. Through a combination of data

reduction and advanced acceleration

techniques, Silver Peak appliances

dramatically improve le access and transfer

across the WAN. Silver Peak ensures

accurate content delivery in a scalable and

secure manner, enabling IT managers to

break free from the challenges of remote

le access and storage.

Network Memory reduces trafc over the WAN and provides LAN-like

performance, without altering client/server communications in any way.

Client request

Server response to request

Instructions sent between appliances to deliver information locally

Appliance intercepts

byte streams of data

Client

Application Servers

Information

delivered locally

WAN

Figure 5. Network Memory reduces trafc over the WAN and provides LAN–like performance,

without altering client/server communications in any way.