Solutions for Accessing in an On-Demand Desktop Streaming Environment

Transcription

1 Solutions for Accessing in an On-Demand Desktop Streaming Environment Product Group Dell White Paper Ananda Sankaran Bharath Vasudevan THIS WHITE PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES. THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND. February 2008

2 Contents Introduction...3 On-Demand Desktop Streaming Overview...4 Streaming Server... 4 Client Machines Access Challenges...6 Access Solutions...8 Private Mode Deployment Archiving Solutions Web Access... 9 Increased Mailbox Size Conclusion...11 February 2008 Page 2 Product Group

3 Introduction Flexible Computing Solutions such as On Demand Desktop Streaming, Virtual Remote Desktop, Virtual Client Desktop, Dedicated Remote Desktop and Application Streaming are increasingly becoming attractive for IT departments due to their centralized management capabilities and low total cost of ownership (TCO). They ease the traditional requirements for deploying and maintaining software on an end user machine s local hard drive, helping to improve the security, manageability and reliability of IT operations required for the end user. The Dell Flexible Computing Solution, On Demand Desktop Streaming, based on the Citrix Provisioning Server for Desktops, enables diskless client computers to boot from a network server. The network server, referred to as the streaming server, delivers disk images containing operating system and applications on demand to client computers over the network. Enterprise e mail applications like Microsoft Exchange Server are well understood and prevalent in today s IT deployments. Accessing e mail in On Demand Desktop Streaming environments using traditional e mail client applications such as Microsoft Outlook can pose new challenges. This whitepaper highlights some of these challenges and provides general best practices for addressing them. February 2008 Page 3 Product Group

4 On-Demand Desktop Streaming Overview The On Demand Desktop Streaming solution includes client systems, streaming servers running Citrix Provisioning Server for Desktops software, infrastructure components such as Active Directory/DHCP/DNS and networking components. An e mail server such as Microsoft Exchange Server is accessible to the client machines via the network and is most likely collocated with streaming server and infrastructure components. Client applications such as Microsoft Outlook running on client machines access the e mail server via the network. Streaming Server The streaming servers maintain and deliver client hard disk virtual disk images called vdisks. A vdisk image is prepared from a master client s hard drive and can be reused across identically configured client machines. A master client is a machine identical to the clients to be deployed with the exception of a hard drive being present. It must be identical to the clients to be deployed to ensure system driver compatibility and should be configured with the operating system, software and settings desired for the clients to be deployed. Once the image has been created, the server can be configured to deliver images to clients in private mode or in standard mode. Private mode delivers one streamed image to one client. Operating in this mode increases the physical security of the client s data, but manageability of images is not addressed. A separate image needs to be maintained on the server for each client. Each client s read and write requests on the local hard disk are redirected to its respective vdisk image on the server. Client writes are saved on its respective image and the state of the image for each client is maintained across reboots. In essence each client exclusively owns its hard disk maintained as an image on the server. User data such as application files or e mail folders can be stored directly on the client s image, similar to a regular hard drive. Standard mode delivers one streamed image to more than one client. In addition to the physical security gained by streaming the data from a secure datacenter, implementing standard mode also decreases the number of images to maintain given the one to many nature of images to client systems. Updates to a single vdisk can be applied to multiple clients when the clients reboot. Client disk read and write requests are redirected to the streaming server via the network. The server satisfies the read requests by delivering the required information from the read only vdisk image and satisfies the write requests by writing data to a temporary write cache located on a server disk volume. The contents of the write cache will be deleted after a client shuts down. Client updates are not maintained on the single shared image and the client is always presented with this gold vdisk image at boot up. Client hard disk writes are cached temporarily during the boot session. Persistent user data such as application files and e mail folders should be stored on other persistent and accessible storage such as Network Attached Storage. February 2008 Page 4 Product Group

5 Client Machines The vdisk image prepared for clients includes the client streaming software agent. The Citrix client software must be installed on the master client to allow the creation of a gold vdisk image. That image is then distributed to each identically configured client system, enabling clients to communicate with the streaming server for all read and write operations. The streaming software redirects all local system drive (usually drive C) read and write requests to the streaming server as network calls. Figure 1 below illustrates this concept. In the standardimage mode, disk writes to the local system drive are redirected, kept on a temporary write cache location and deleted at the end of the user s session. The local system disk (if present) can be used for writing temporary data. Persistent application data should be stored on appropriate network shares or locations outside of the streamed image. During operation, clients utilize local resources such as CPU, memory and GPU for all computational operations and processing. Disk requests are the only local operation redirected to the streaming server. Figure 1: Client disk requests to streaming server Typically, during boot, the client requests the initial OS binaries required for booting and displaying the desktop. Additional OS binaries, application binaries and data are requested by the client on demand as required during operations. February 2008 Page 5 Product Group

6 Access Challenges The standard mode deployment of the On Demand Desktop Streaming solution includes a readonly gold vdisk image on the server, which is presented as a local hard disk to client machines booting from that server. Since the image is read only, all client machine disk writes are temporarily cached on the server. Because the client machine hard disk writes are not persistent, non committed data would be lost at the end of the boot session. Any end user data that requires persistent storage, such as files and personal e mail folders, needs to be stored on the network and accessible to client machines. Network Attached Storage (NAS) solutions that offer storage space as home drives to user data are common today. Such solutions can be utilized in the standard mode deployment for end users to store their persistent data (Figure 2). The NAS Appliance depicted in the illustration is for sample architectural reference only. A variety of commercial NAS solutions are available today based on various storage hardware and can be deployed for storing user data. Streaming Server (License / IO) Infrastructure (DHCP/DNS) NAS Appliance (User Data) LAN Clients Figure 2: User persistent data in Desktop Streaming stored on NAS Typically with e mail applications, such as Microsoft Exchange, end users are provided with an e mail mailbox which is hosted on the Exchange servers. Administrators designate a mailbox quota for users, who are unable to send/receive s if they exceed this quota. It is common for users to overcome the mailbox size limitation by archiving or filing excess e mail in offline mail folders. These mail folders are stored as files on the local hard drive of the personal computer. Optionally these mail folder files are backed up to other persistent storage such optical discs, hard drives or tape backups that may be centrally managed by IT departments. In the standard mode deployment of the On Demand Desktop Streaming solution, the local disk presented on February 2008 Page 6 Product Group

7 the personal computer is non persistent and hence cannot be used for storing offline mail folders. The mail folder files have to be stored and accessed from a network location such as a NAS solution. The Microsoft Outlook client application that works with the Microsoft Exchange e mail solution does not support storing these personal mail folders on a NAS appliance. These personal folder files, often referred to as pst files, are architected to function from a local hard disk and not from a central NAS like storage solution. Microsoft does not support pst files stored on the network. (For more information, refer to Microsoft support knowledge base article ) Similarly when the Microsoft Outlook client application is configured in cached mode, an offline mail folder file, called an ost file, is created on the client hard disk. The user s mailbox, hosted on the e mail server, is cached in this file folder and is periodically synchronized with the server. Microsoft does not support ost files hosted on network solutions, as indicated in the same knowledge base article. It must be noted that other Microsoft Windows network methods, such as folder re direction and domain profiles, are also not suitable to store e mail folders as they usually are based on NAS solutions. For the above reasons, personal folders and offline folders with the Microsoft Outlook / Microsoft Exchange solution cannot be stored on network locations. Therefore, in a standard image mode desktop streaming environment, alternate methods need to be considered for staging offline user mail that is based on the Microsoft Outlook solution. It is also important to understand that cached mode operation of Microsoft Outlook is not supported with the standard image mode deployment. The following sections explore some alternative methods that can be implemented to overcome this limitation. February 2008 Page 7 Product Group

8 Solutions for Accessing Private Mode Deployment The private mode deployment of the On Demand Desktop Streaming solution can be considered as an alternative for overcoming the requirement of storing pst files on a NAS solution. In private mode, each client machine that is part of the On Demand Desktop Streaming deployment has its own separate image stored on the streaming server. This image is streamed and presented as the hard drive to the client. All client machine writes, including writes to pst e mail file folders are stored back on the corresponding image on the server. Because of this, all user offline e mail folders get stored on the client hard drive that is stored as an image. The advantages of this approach include increased data security and reliability. User e mail data is stored on an image in the data center, protecting against physical theft and also enabling centralized backup/restore of data. Some limitations of this approach include the lack of single image management that comes with the standard mode deployment. Maintenance activities such as upgrades and patches need to be applied to each client machine image separately, as though they were independent traditional client machines. Also, if multiple users are sharing a single client machine for their computing needs, then all their offline e mail data would be stored in the same image. Proper segregation needs to be ensured on the image, with security and access permissions that allow users access only to their own e mail data on that image. It must also be understood that offline user e mail data will not be automatically migrated across client machines. If a user requires access to e mail data on a different client machine, then the data from the first machine needs to be copied to the second machine directly or via a temporary network share. User portability across client machines incurs this limitation. Another aspect that requires consideration is the performance of the solution in private mode deployment. The server will be streaming separate images to each client and the caching benefits of using a single image may be lost. Also, the amount of client e mail data stored on each image would be significant, leading to an increase in data flowing across the network to the server. Additionally, in this style of deployment, administrators still need to deploy anti virus software and anti spyware software which can continuously scan the user s image. The impact of these constant IO operations running simultaneously for numerous clients may have adverse effects on the server resources. The streaming server and the network infrastructure should be suitably designed to handle these situations. Archiving Solutions E mail archiving solutions are becoming increasingly important in today s Enterprises. These solutions include Symantec Enterprise Vault and EMC Xtender. E mail archiving solutions offer an offline storage repository for storing and archiving user e mail that exceeds the quota assigned to user mailboxes in the e mail server. The archiving solution repository is separate from the mailbox server and includes its own hardware and software data center components. Archiving solutions provide access to the offline e mail storage to end users directly from their client machines even when the mail server is not available. Archiving solutions enable extending February 2008 Page 8 Product Group

9 the size of user mailboxes by providing offline storage to host user e mail. Users can seamlessly access e mails stored both in their mailbox and the archiving solution. The On Demand Desktop Streaming solution can be deployed in the standard single image mode along with support from a suitable e mail archiving solution for hosting offline user e mail (Figure 3). Streaming Server (License / IO) Infrastructure (DHCP/DNS) NAS Appliance (Other User Data) LAN Archiving Solution (User Data) Server Clients Storage Figure 3: Archiving Solution with Desktop Streaming Archiving solutions provide several features and advantages besides providing offline repository for user e mail. They enable businesses to achieve legal and regulatory compliance by providing mechanisms to manage, store and retain user e mail data based on policies. Features such as journaling allow classification and storage based on business policies. They also provide users the ability to manage and store e mails based on personal policies. Archiving solutions also provide the benefits of centralized physical security and reliability from data loss. Limitations of archiving solutions include additional cost, planning and maintenance associated with a separate data center solution. Implementing an archiving solution merely to overcome the offline e mail storage problem with the standard mode streaming deployment may not be cost effective. Web Access E mail solutions typically provide user access to mailboxes via a standard Internet browser application. The Microsoft Exchange Server application provides user access to mailboxes via a feature called Outlook Web Access (OWA). OWA enables users to use a standard Internet browser such as Microsoft Internet Explorer and connect to Exchange Server to log in and access their mailboxes. In the standard mode single image deployment, users can access e mail from any client machine on the network in the deployment. User e mail resides centrally on the mailbox server, and no user e mail data is stored on the client image. User ability to store e mail data on February 2008 Page 9 Product Group

10 the client image can be restricted by not installing e mail management client applications such as Microsoft Outlook on the client image. E mail web access solutions do not require the installation and maintenance of e mail client applications on the shared client image, which can reduce associated licensing and maintenance costs. User access to e mail becomes operating system (OS) agnostic, and users have the ability to access e mail using a standard Internet browser application from any client machine. Higher education environments often utilize web access to because of the mobile nature of students, coupled with the variety of OS environments that must be supported on campus. Web access solutions may limit user experience by not including all the features available on a standard e mail client application. Further user mailbox size is limited to the provisioned size on the mailbox server and users need to manage their mailbox space themselves. This approach is more suitable for deployments where end users require access but do not incur heavy usage. Increased Mailbox Size A simpler approach to overcome storage of personal e mail folders on a single shared client image would be provisioning larger mailbox sizes for end users. All user e mail data is stored on the respective mailboxes, hosted on the mail server, and remains accessible at all times from any client on the network. Users need not store excess e mail in personal folders on the client image. Advantages of this approach include central management of e mail data and physical security. However, the cost per mailbox for IT operations increases due to the additional storage hardware required for larger mailboxes and the associated maintenance costs. In addition, existing IT procedures and policies on mailbox quotas need to be modified to accommodate this approach. February 2008 Page 10 Product Group

11 Conclusion Dell s On Demand Desktop Streaming solution provides significant benefits such as data security, reliability and centralized desktop manageability to IT departments. It is a relatively new client computing model in Enterprises and can introduce new challenges with existing traditional client server applications. One such challenge is the storage of user e mail as offline folders on the client machine hard drive. This paper highlights a set of options that can help overcome this challenge. Additional options may be feasible based on the requirements of the deployment. Nevertheless, it is recommended that the application requirements be carefully assessed and the co existence impacts with the streaming solution be carefully analyzed before deployment. These requirements include the end user computing needs as well as the IT operational needs. February 2008 Page 11 Product Group