The 2010 Guide To Iscsi Storage

WHITE PAPER

The 2010 Guide to iSCSI Storage The Essential Guide to iSCSI Storage and Why You Should Convert Your Windows Server 2008 R2 Into Shared Storage on Your Existing Ethernet / IP Network

Introduction

“

iSCSI storage is already in use by many companies from SMBs to the Fortune 500s.

”

This guide provides an overview of why you should consider using iSCSI storage in your IT environment. Helping answer the question; why implement iSCSI storage when you can also select from NAS (Network Attached Storage / also know as your file servers), DAS (Direct Attached Storage, i.e. local hard disks), or FC (Fiber Channel)? Building your own iSCSI SAN using off the shelf hardware and freely available iSCSI storage software is a fairly easy task. But why bother with an iSCSI SAN at all? With an iSCSI SAN you can do many common tasks far easier and faster than with conventional file servers and direct attached disks. A SAN gives you “shared storage” on your network, meaning that you can centrally manage all of your storage from one device as opposed to managing storage on each application server. Shared storage has many advantages, including enabling simplified backups when using snapshots, and allows replication between storage devices, for offsiting data, to be done at a far lower cost than with host based replication. This whitepaper details what iSCSI is, demystifies some common misconceptions you may have about iSCSI, and outlines why iSCSI could be the best choice over FC, DAS or NAS. Furthermore, using off the shelf server hardware and iSCSI storage software available as free or paid editions enables you to build your own SAN and lowers the cost of entry for budget challenged IT departments, without limiting functionality and scalability. iSCSI storage is already in use by many companies from SMBs to the Fortune 500s. Questions we will answer for you: 1. What is iSCSI and why should you care? 2. What iSCSI means to those who consider networked storage to be too expensive? 3. What you need to implement a SAN that works over your Ethernet? 4. How does an iSCSI SAN compare to a Fibre Channel SAN in cost and performance?

[2] www.starwindsoftware.com

What is iSCSI? SCSI (Small Computer Systems Interface) has been a standard protocol for decades, which enables computers to communicate with storage devices. As system interconnects move from the classical bus structure to a network structure, SCSI commands must be mapped to network transport protocols. Today’s IP Gigabit networks meet the performance requirements of to seamlessly transport SCSI commands between applicaiton servers to centralized storage. The iSCSI protocol enables the transfer of SCSI packets over a TCP/IP (Ethernet)network. iSCSI is an interoperable solution which enables the use of existing TCP/IP infrastructure and addresses distance limitations (iSCSI can also be used over the Internet). This means the disk drives in your SAN are presented over your existing Ethernet network to server applications as though the disks are local to your physical server hardware. Don’t confuse this with traditional SCSI disks; in fact, iSCSI storage is typically implemented with affordable SATA or SAS disks. iSCSI presents block based storage just as you get with your internal disk drives, whereas a NAS is nothing more than a plain file server which presents storage as file shares. A common scenario is to use a portion of your iSCSI SAN storage as back-end disks for file servers (NAS), consolidating both application data and file shares into one iSCSI allows any IT appliance.

administrator to easily deploy a true SAN over an IP network.

With iSCSI storage you can use any IP switches and routers, and the client machines (your servers) can use a software driver called an “initiator” instead of the more costly FC HBAs (Host Based Adapters). For older servers with lower powered CPU’s you can use an iSCSI HBA which is still lower cost than a FC HBA. Both StarWind Software and Microsoft provide freely downloadable software iSCSI Initiators. Microsoft has eagerly endorsed iSCSI technology for Windows, helping to promote iSCSI awareness. The concept of using an IP network for block based storage causes many people to incorrectly assume storage traffic will clutter their LAN, or that IP networking may not provide the necessary performance your applications require. While it is true that many early iSCSI vendors were shipping products that were not up to the job of enterprise class applications such as Microsoft Exchange, VMware and SQL Server, there

[3] www.starwindsoftware.com

is also a well established base of vendors that are shipping iSCSI storage into SMBs and enterprise customers. Keep reading to learn the truth about iSCSI. iSCSI Storage is often referred to as an “iSCSI Array” or “iSCSI Target”. The official terminology uses “Target” to refer to the storage side and “Initiator” for the client side driver. The Initiator allows application servers and workstations to access the Target (the iSCSI storage).

Benefits of iSCSI The iSCSI protocol provides numerous benefits for SANs compared to using Fiber Channel, a few key points are summarized below: • iSCSI uses familiar networking standards: Ethernet and TCP/IP. Most IT administrators are already familiar with TCP/IP, unlike the more complex skills required for FC storage. • Total storage costs are reduced: iSCSI SANs are easier to install and maintain than FC, lowering installation and maintenance expenses. iSCSI reduces the necessity of hiring or outsourcing storage administration. • Replication works over a standard IP network: iSCSI replication eliminates distance limitations and costs associated with FC routers. • Reduces complexity by eliminating Fibre Channel switches and cabling: Using standard Ethernet switches simplifies everything as most organizations already have in house IP networking skills. • iSCSI scales to 10 Gigabit: For enterprise applications that require high transactional performance 10GigE is available, thus expanding iSCSI Storage Networks performance to equal the performance of Metro and Wide Area Networks.

Long Distance Storage iSCSI’s use of IP Networking means long distance is no longer an issue for backing up remote sites or performing disaster recovery. With the use of Secure Internet Protocol (IPSec) and Secure Sockets Layer (SSL) to provide authentication and privacy iSCSI over a public network is a viable method to extend the corporate network without incurring high costs. 10 Gigabit Ethernet provides enough bandwidth and

reliability to transfer large amounts of data over long distance IP networks.

Who Can Use iSCSI Any company that places a high value on their data can benefit from an iSCSI SAN. Including: • Any IT shop with limited resources and limited budgets. iSCSI is a proven technology that costs significantly less than Fiber Channel, and provides superior data protection and cost reductions over traditional direct attached disks (also refered to as DAS). • iSCSI is fully supported by VMware and many other virtual machine vendors: in most cases an iSCSI SAN is the best choice for server virtualization projects. • Designers and testing and development teams that require immediate and fast access to data and backup sets, without waiting for delays with traditional tape based backups. • When data is required in real time across geographically distributed organizations iSCSI makes the best sense due to the low cost and ease of use of IP Networking. • Organizations that host other people’s data such as Application Service Providers (ASPs), Internet Service Providers (ISPs) or Storage Service Providers (SSPs) can all benefit from a reduced TCO footprint when using iSCSI storage. • Anywhere remote data replication or disaster recovery is a requirement: Typically as organizations start to expand i.e. a new office is opened or a new company is acquired in another state, the costs associated with traditional data protection such as tape off-siting and data center hosting costs can be significantly reduced by leveraging remote sites and iSCSI. • Even the smallest companies can seek a postitive ROI when using iSCSI storage to backup straight to disk before going to tape, essentially retaining weeks or even months of backups for protection against data loss and for legal/compliancy requirements. Thus reducing the dependency on backup tape.

Mixed Storage Environment - iSCSI and FC It’s important to mention that iSCSI storage can work in a [4] www.starwindsoftware.com

mixed protocol environment. For example if you have a need for additional storage and already own a FC SAN which you don’t plan to replace, then iSCSI may be the most rational decision for A) new virtual machine deployments B) application servers that are not SAN attached but have out grown their direct attached disks C) as an iSCSI disk-to-disk backup appliance or D) a pure VTL (virtual tape library). For organizations already invested in FC as primary storage which require lower cost Tier 2 storage, using iSCSI for the lower cost tiers will provide significant cost savings over FC. It’s a growing trend within the industry to implement iSCSI storage in mixed protocol environment, where existing FC storage may be legacy but still under warranty, or the performance of FC is required for extremely I/O intensive applications such as high transactional databases with many hits per second, leaving iSCSI as the ideal choice for many applications from Microsoft Exchange, SQL Server to VMware or Hyper-V.

Performance One of the main advantages of iSCSI is speed. iSCSI storage is Ethernet-based so IT Administrators only require basic IP networking knowledge, as opposed to more specialized FC networking skills. There is a common misconception that FC provides better performance, yet with correct sizing to determine the appropriate speed and number of disks needed in each RAID group to achieve the required IOPs (i/o’s per second) to sustain optimal application performance, iSCSI has proven to be capable of meeting the performance requirements of some of the most demanding applications in the enterprise. Plus FC storage is significantly more expensive, requiring proprietary FC HBAs (Host Based Adapters) on client machines as well as more expensive FC network switches. Also, managing and maintaining a FC SAN requires administrators to learn new skills in FC networking. While the price is significantly higher for FC, the performance is not 300% better. Ultimately, what everyone has begun to realize is that while Fibre Channel bandwidth is theoretically higher, bottlenecks in performance become non-issues with correct sizing of a SANs disks (number of spindles per RAID group and speed of drives) and the appropriate number of IP network connections (multi-pathing) between your application servers and the iSCSI Storage.

IP Networking iSCSI storage allows you to use existing IP switches and routers, and the client machines (your application servers) can use basic software called an “initiator” instead of more expensive FC HBA cards. For older application servers with lower powered CPU’s you can use an iSCSI HBA which is still affordable

unlike the FC HBA counterpart. For instance, Microsoft offers a freely downloadable software iSCSI Initiator and all new versions of Microsoft Windows include the Microsoft iSCSI Initiator. Microsoft has eagerly endorsed iSCSI technology for Windows, helping to promote iSCSI awareness. Linux based iSCSI initiators are also freely available. One misconception of iSCSI is that it puts traffic onto the corporate network. This is not true, as iSCSI storage can be configured as a true SAN by placing the iSCSI servers on a segmented network, either by using physically separate switches / host ports or by configuring VLANs on existing Gigabit Ethernet switches. Also, using jumbo frames can improve performance by 15% or more. To make sure that your IP network is utilized correctly, you should use a dedicated NIC port on your application servers to connect to dedicated IP switches which are only used for iSCSI traffic. This will ensure that you don’t overwhelm your LAN. This is the cornerstone of a SAN which is by definition a separate network for storage. For further redundancy on your SAN network you can use two separate switches in a crisscross fashion, this requires either dual NICs or two available Ethernet ports on your application servers. To clarify a common point of confusion an iSCSI HBA is not the same as an iSCSI offload or TOE (TCP Offload Engine) NIC. An iSCSI HBA is a dedicated hardware based initiator (which may also include an Ethernet port with TOE). TOE NICs and iSCSI offload NICs still require a software based initiator such as the freely available Microsoft Initiator or the more advanced StarPort Initiator from StarWind Software.

Sizing Disks Sizing disks involves selecting the correct speed drives and the right number of drives per RAID group to achieve the required IOPs (i/o operations per second) for your applications. How you decide to carve up a RAID group, many LUNs spread across a single RAID group vs. each LUN on a separate RAID group is a function of the performance your applications require.

Security Now a little about iSCSI security which is achieved by the design of iSCSI enabling IT administrators to specify the client machines (Initiators) that are able to connect to the iSCSI storage server (the iSCSI Target). CHAP (Challenge Handshake Authentication Protocol) is used to provide authentication with iSCSI storage devices. Because CHAP identifiers are changed [5] www.starwindsoftware.com

frequently and because authentication can be requested by the SAN at any time, CHAP provides a high level of security, even more so than Password Authentication Procedures (PAP). iSCSI Initiators provide an authentication capability to prevent unauthorized servers from accessing storage. Deploying the iSCSI SAN in a secure data-center environment usually provides sufficient security for most environments. If the SAN extends over a campus or a metropolitan area, you can also implement IPSec protection.

Virtual Machines and Server Consolidation Now that vendors such as VMware fully support iSCSI storage, IT shops can be confident that an iSCSI SAN may indeed be the best choice for a virtual server environment. In most cases an iSCSI SAN that is correctly sized for your applications performance requirements will deliver the needed throughput to ensure application performance and availability. That being said, even FC, when poorly sized may not perform as required. When using virtual machines such as with VMware or Hyper-V, shared storage greatly simplifies and leverages the flexibility and portability benefits that come with not having your application server tied to a single piece of hardware. Utilizing features like VMware’s VMotion, VCB, DRS and VMware HA or Microsoft Hyper-V’s Live Migration which are key drivers of any virtualization implementation. Shared storage is not an option when implementing this type of strategy, it is a requirement. For assistance with designing your storage with virtual servers please contact your SAN vendor or you can look at StarWind’s Essential Guide for VMware High Availability with Shared Storage. Using shared storage makes it significantly easier to manage, provision and protect virtual machines. This combined with server consolidation make up the bulk of the ROI associated with any virtualization implementation, cost effective shared storage options are the glue that helps maintain this ROI, preventing IT departments from watching these saved dollars evaporate at the expense of a FC SAN.

Data Protection: Leveraging Replication and Snapshots Replication (sometimes referred to as mirroring) and snapshots are two of the more powerful benefits of a SAN. A feature of replication is CDP (Constant Data Protection) which allows near real time data protection between storage devices located either remotely (between offices) or locally for backup and disaster recovery plans. Snapshots allow you to easily create a full copy of your data, or create a backup of just the changed data since the last full copy. Some SAN vendors

separate snaps from clones as separate paid options, so take note of how your SAN vendor prices each option as other vendors provide all features included with the base price. Replication allows you to set up a redundant iSCSI server to protect data, CDP allows recovery of current data as opposed to restoring an older file that may be a few hours out of date. Since iSCSI processes all data on the iSCSI server there is no overhead on your application servers when performing backup tasks using an iSCSI server snapshot and using replication features.

Where Does Tape Fit in? What if you don’t need to reinvent your entire storage methodology, what if you are getting by, and you just need a better way to manage backups? iSCSI is a perfect solution here since you can perform backups from your application and file servers direct to iSCSI instead of going straight to tape. For extra data protection you can still backup to tape after going to iSCSI, i.e. disk-to-disk-to-tape. Also, many iSCSI vendors provide a VTL (Virtual Tape Library) option so your backup software agents see the iSCSI storage as though it is a tape library, thus requiring no changes to your backup software. To backup without the VTL option your backup software must be capable of backing up straight to disk, usually this entails an additional paid option unless you already own the feature.

consolidate storage, providing easier management as well as faster and simpler expansion through one single management point. Also, Thin Provisioning is a key feature of higher end SANs, allowing you to provision more storage than is physically available, thus allowing you to add disks on the fly as storage demand grows, without reconfiguring your application servers. NAS storage (file servers) can be used in conjunction with iSCSI storage, to provide a file server for your desktops and workstations. This way desktops can connect to a file server which connects to iSCSI storage in the back end, eliminating the need to use a client side initiator on desktops, and all your applications such as SQL Server and Microsoft Exchange can connect directly to your iSCSI storage.

Boot From SAN For organizations interested in eliminating local hard disks entirely (including the disks where the operating system is installed) it is also possible to boot servers and desktops directly from iSCSI storage, typically referred to as “boot from SAN”. Using an iSCSI boot capable NIC, an iSCSI HBA or iSCSI Boot software you can boot your entire Windows or Linux OS from iSCSI storage. Boot from SAN greatly simplifies provisioning and disaster recovery for servers where virtual machines are not a good fit, either due to financial constraints or for applications that require a dedicated physical machine.

Selecting an iSCSI Solution Backing up to iSCSI storage requires fewer tape backups, provides more efficient restores (restoring from iSCSI is many times faster than restoring from tape), and your backup windows will be significantly reduced. How much data you decide to keep on disk is a function of your data protection strategy, typically a minimum of 4 weeks of backups should be kept on disk, to as many as a year. The cost of disks needs to be balanced with the value of your data and the current costs of backing up straight to tape and trucking the tapes offsite.

What about DAS and NAS? With DAS (Direct Attached Storage, also known as local attached disks) the utilization rate is typically only 30-70%, leaving a lot of wasted storage space. Managing storage spread across multiple servers is not an ideal situation, especially if you need to add more storage capacity. If you use or plan to use virtual machines such as VMware or Hyper-V then shared storage is essential to leveraging the full benefits of virtual machines such as VMware’s VMotion capabilities to live migrate servers between physical machines. iSCSI storage helps [6] www.starwindsoftware.com

There are many iSCSI vendors today with an assortment of products available to provide iSCSI storage. The critical factors to consider when selecting iSCSI storage is the performance of the appliance and the feature set required to manage the storage. Some vendors charge high prices for enterprise features such as snapshots and replication, while other vendors may include all features but charge a significantly higher entry fee, with costly proprietary vendor lock-ins for future storage expansion. And beware of low end all-in-one hardware, these devices usually have limited performance due to low powered CPUs, limited NIC ports and limited software management capabilities. One of the easiest ways to implement iSCSI storage is to build your own storage server using a standard off the shelf server (HP, IBM, Dell, etc) and install iSCSI Target Software such the Free version of StarWind Server v4.1 for Microsoft Windows, which gives you plenty of flexibility for use as primary storage for application servers such as Exchange or virtual machines such as Hyper-V and VMware ESX, for Tier-2 storage for less

critical applications and file servers, for pure disk-to-disk backup or even as a dedicated VTL (virtual tape library). The Free edition of StarWind allows you to manage a capacity of up to 2TB. Once you download and install StarWind iSCSI Server software, it should take you no more than 15 to 20 minutes to get started. StarWind can be installed on any x86 server running 64-bit or 32-bit Microsoft Windows, allowing you to select your preferred hardware vendor (i.e. Dell, HP, IBM, or any white box server ) or to repurpose any existing server that may have become available after consolidation or implementation of VMware or Hyper-V virtualization environments. StarWind is also available in paid editions that support replication, CDP, snapshots and VTL functionality.

Figure 3: Creating a new virtual disk in StarWind with Encryption enabled.

Figure 1: StarWind central management console interface, showing two active devices. A device in StarWind contains data such as primary storage or snapshots.

Figure 4: Configuring snapshots in StarWind, using the option to auto-snap every 30 minutes.

Figure 2: Adding a new client connection to StarWind. Note the option to enable CHAP authentication for security. [7] www.starwindsoftware.com

StarWind specifics In large I/O environments adding more NIC ports to the StarWind server will allow even more data throughput. Unlike many dedicated SAN vendors, a StarWind SAN allows you to grow NIC ports without purchasing new dedicated SAN hardware. Also, ensure you are using a 1GigE network for all SAN traffic. Anything slower will likely not provide enough network bandwidth for most applications.

Initiator is used to enable the client machine to connect to your new SAN. StarWind has also been validated with Linux and UNIX iSCSI initiators, iSCSI HBAs from Adaptec and QLogic and hardware iSCSI accelerators from Alacritech. Multi-pathing will provide redundancy or NIC teaming to improve data flow. Multi-pathing with StarWind is achieved using industry standard MPIO capabilities. If you are using StarWind as a backup to disk appliance and you only have a single backup server you can get away with a simpler direct connection and eliminate a switch all together.

On Windows clients (your application servers) the free Microsoft iSCSI Initiator or the free and more advanced StarPort

NOTE: This diagram illustrates segmenting the iSCSI network (the SAN) from the corporate LAN. Two IP switches are used for redundancy.

[8] www.starwindsoftware.com

Summary

Related Links

Storage Virtualization has rapidly become a standard technology for use in software development, testing, and server consolidation scenarios. A growing trend is for organizations to further leverage storage virtualization to achieve superior results using iSCSI over an IP network.

To download a fully functional FREE edition of the StarWind iSCSI Server for Microsoft Windows or for more information from StarWind Software about the solution outlined in this paper visit: www.starwindsoftware.com.

iSCSI technology is proven with many customer installations, providing low cost high performance alternatives to legacy Fibre Channel SANs, Direct Attached storage or Network Attached Storage. iSCSI runs over Ethernet on off the shelf hardware, and provides enhanced features for virtual server environments. iSCSI storage provides the benefits of enterprise class functionality previously only available with more costly FC storage, with the low costs preciously associated with DAS. iSCSI is also an ideal complement to existing FC infrastructure. iSCSI is a particularly appealing choice for SMB’s as it does not require specialized equipment or training, making for a simple solution that is highly affordable. This guide is meant to be a brief introduction to iSCSI and how it compares to other storage solutions. Please refer to the Build a SAN Guide, and consult your sales rep for further assistance.

ABOUT STARWIND

Since 2003, StarWind has been the storage solution of choice for thousands of global customers in over 50 countries, from SMBs, to governments, and to Fortune 1000 clients. StarWind has pioneered the iSCSI / IP SAN industry with its storage virtualization software that converts any Windows Server into a reliable and scalable shared storage.

Turn Any Server Into a SAN. Enterprise Features. SMB Price.TM

www.starwindsoftware.com

Portions © StarWind Software Inc. All rights reserved. Reproduction in any manner whatsoever without the express written permission of StarWind Software, Inc. is strictly forbidden. For more information, contact StarWind. Information in this document is subject to change without notice. StarWind Enterprise Server is a registered trademark of StarWind Software. 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.