All About SANs


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Storage area networks (SANs) are one of the options that growing businesses can turn to when it’s time to upgrade their storage infrastructure. As with any major technology purchase, it’s important to do your homework when shopping for a SAN.

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All About SANs

  1. 1. Data storage strategies andData Storage Insights insights for growing businesses All About SANs In this issue:ComparingSAN protocolsSANshopping listSANsand virtualenvironments Issue 3, 2011
  2. 2. Contents… Data Storage Insights Contributors: Drew Robb and Paul Rubens.2 2 All About SANs 3 Comparing the Most Popular SAN Protocols3 6 6 The IT Administrator’s SAN Shopping List 9 Why SANs Make Sense for Virtual Environments9
  3. 3. Data Storage Insights All About SANs S torage area networks (SANs) are one of the options that growing businesses can turn to when it’s time to upgrade their storage infrastructure. As with any major technologypurchase, it’s important to do your homework whenshopping for a SAN.In this issue of Data Storage Insights we’re going toreview the most important aspects of a SAN to help ITmanagers make an informed purchase. We start with acomparison of the two most popular SAN protocols —Fibre Channel and Internet SCSI (iSCSI) and the case forusing either protocol in your business.We’re also going to review a checklist of the things thatIT administrators need to know when shopping for aSAN, including a review of disk arrays, managementsoftware, host bus adapters, storage switches and more.Finally, we’re going to look at networked storage foryour virtual environment and why a SAN is the smartchoice to make. Many growing businesses are beginningto explore server virtualization if they aren’t alreadyusing it in their data centers. How they will store data inthis virtual environment is a question that needs to beanswered early in the process.After exploring the ins and outs of storage area networkswith this issue of Data Storage Insights, you’ll be in abetter position to make an informed buying decision. 2 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  4. 4. Data Storage Insights Comparing the Most Popular SAN Protocols By Drew Robb M ost storage area networks (SANs) are deployed using one of two protocols: Fibre Channel (FC) or Internet SCSI (iSCSI).“iSCSI and FC are both block transfer protocols thattransmit the SCSI command set across a network to createa storage area network,” said Howard Marks, Founderand Chief Scientist at which is a better fit for your business’s data storageneeds? Like most questions of this nature, the answerdepends on a large number of factors.The Case for iSCSIiSCSI uses standard Ethernet and Internet Protocol (IP)to transport the SCSI commands. As such, one of thebig advantages of iSCSI is that it leverages the samenetwork knowledge that organizations already have in “It requires additional knowledge and training.”house. In other words, for organizations that don’t haveFC know-how within the enterprise, the deployment of an Hiring staff with sufficient FC SAN savvy, therefore, isiSCSI SAN will be a whole lot easier as existing personnel a factor that has to be considered for those looking toshould be able to install and manage it without having to deploy a SAN. And those personnel probably won’tlearn new skills. come cheap. But that isn’t the only added expense that goes along with FC. Marks characterizes Fibre Channel“If you’re not already using FC I can see very few gear as being significantly more expensive than itsenvironments where I would advise building a new FC Ethernet equivalent. It requires its own switches, Host Businfrastructure,” said Marks. “By using iSCSI, you can Adapters (HBAs) and disk arrays that can be a dauntingsave money and avoid having to send some of your investment for those establishing their first SAN. That’s aadministrators off for Fibre Channel training.” big reason why many SMBs gravitate to iSCSI as their first foray into advanced storage networking.Fibre Channel, on the other hand, is a networkarchitecture used only for SAN transport. Companies The Case for Fibre Channeldeploying it have to employ SAN administrators as thetechnology is very different from traditional networking. But it isn’t an open and shut proposition. The big reason why an FC SAN is necessary in some shops boils down to“Most network guys find FC arcane at best,” said Marks. performance. 3 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  5. 5. Data Storage Insights“Fibre Channel can deliver lower latency and plus for FC. Its large installed base gives it a uniquetherefore better performance for the most demanding position that distinguishes it from other storage transportapplications,” said Marks. technologies. This has led to a steady stream of FC features and enhancements that promise to give iSCSIThat’s why boutique financial businesses and other IT- a run for its money in the coming years. While mostcentric firms often bypass iSCSI and implement an FC existing sites use 1, 2 or 4 Gb FC, newer gear featuringSAN. While the initial cost may be higher, they gain in 8 Gb FC already dominates in terms of number of portsthe long run due to improved transaction times. The shipped, according to Dell’Oro Group numbers. Andprice tag for the SAN is dwarfed by the revenues that can within a couple of years, 16 Gb FC and Fibre Channel overpotentially be lost due to slow transaction times. Ethernet (FCoE) ports will take the lead.In addition, server and storage OEMs are doing a FCoE even threatens to eliminate the entire iSCSIbetter job of packaging their hardware to make it more versus FC argument as both protocols utilize anaffordable. Mergers within the industry have resulted in a Ethernet network. The advantages of FCoE are lesssteady fall in the price of introductory FC SAN hardware, hardware, cabling, installation, management and lowermaking it a more attractive option, particularly for those cost by reason of converged storage and networkingwith higher performance requirements. infrastructure.Blurring the Lines “When you take switches, cabling and adapters into account, FCoE is 33 percent cheaper to deploy thanWhile those are the traditional arguments concerning traditional networks and holds the promise of 50 percentiSCSI versus FC, the lines are blurring as technology savings on power and cooling,” said Bob Laliberte, anadvances. On the iSCSI side, the latest bump in Ethernet analyst with Enterprise Strategy Group (ESG). “Longspeed goes a long way to resolving its performance term predictions are that most connectivity options areshortfall. Instead of the usual 1 Gb speeds, a newer focused on Ethernet-based transports.”standard known as 10 Gb Ethernet (10GbE) providesa major hike in throughput. That has caused some to ESG placed adoption of this technology at only 9wonder if Fibre Channel really has a future. percent of users at the end of 2010. That should rise to more than 25 percent by the end of near year. TheBut 10 GbE gear also comes at a premium, though prices reasons for the relatively slow ramp up include costare gradually falling. Further, firms deploying this new and technological maturity. The vendor world has beeniSCSI platform may find that their existing infrastructure taking its time bringing FCoE products to market; andjust isn’t up to the task. those implementing it face a significant amount of costly infrastructure change-out and upgrade. Yet the promise“iSCSI over 10 Gb Ethernet provides more performance of FCoE is enticing: a single network that can run iSCSI onthan a two-socket Intel Xeon server can use,” said Marks. IP plus FCoE concurrently.His suggestion is that FC is preferable for organizations But not everyone is convinced that Ethernet willwith more than 200 servers, as a robust SAN means they eventually gobble up all FC traffic. The FCIA is pushingcan take advantage of the additional management tools along its roadmap for 16 Gb and 32 Gb Fibre Channel.available for FC while maintaining expected performance The association is aiming for 32 Gb products to hit thelevels. market by around 2014. They will come with a host of new features including higher levels of managementTom Hammond-Doel, Vice Chairman of the Fibre sophistication, storage virtualization and energyChannel Industry Association (FCIA), points out another efficiency. 4 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  6. 6. Data Storage InsightsSummaryThe question about whether to deploy iSCSI or FC usedto be a simple matter. But innovation on both sides hasclouded the issue. Those attempting to reach a decisionare advised to find a vendor or partner that offers bothtechnologies as they can help determine which protocolwill provide the most value within a specific environment.In some cases, it may turn out that the answer is acombined implementation of FC and iSCSI.Stuart Miniman, a Principal Research Contributor for TheWikibon Project, even goes so far as to state that it is afalse argument to pit iSCSI vs. FC (or FCoE).“iSCSI is generally is small environments with amanagement team that handles the full spectrum ofserver/storage/network while FC deployments aretypically much larger and are managed by a dedicatedstorage team,” said Miniman. “There are lots ofcustomers that use both — FC for the bulk of storage andiSCSI for branch office, test/dev or other environmentswhere it makes sense.” 5 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  7. 7. Data Storage Insights The IT Administrator’s SAN Shopping List By Drew Robb I t’s time to invest in a storage area network “Disk arrays also support various availability features (SAN) to increase your storage capacity and including different RAID levels, snapshots, replication improve efficiency. It is vital, therefore, to and high availability such as dual controllers and failover understand what to look for in a SAN before capability,” said Greg Schulz, an analyst with Server anddeciding where to invest storage resources. Here are StorageIO Group.some items to consider in the SAN shopping list. Storage SwitchesDisk Arrays It is the storage switch thatDisk arrays form the backbone provides the secret sauce thatof any SAN. They host large creates the SAN “fabric.” Thesequantities of data that can be switches come with multipleaccessed by any server in the ports of various kinds to connectcompany. As well as proprietary all the cabling. These switchessoftware, controllers and other route data from the servers togear, the disk array contains a the disk arrays.large number of disks — eitherhigh capacity but slower SATA, Some SAN switches arespeedier SAS (but with lower dedicated to a particularcapacity) or Fibre Channel protocol or interface such as SASdisks (FC) that offer the highest or Fibre Channel while othersperformance. Further, arrays are such as iSCSI or FCoE can useavailable that mix and match Ethernet or enhanced Ethernetthese kinds of disks into tiers based switches. Some SANof storage so that key applications are given priority on switches support a mix of Fibre Channel and Ethernetfaster disk. There are even models on the market these for iSCSI (or NAS) as well as Fibre Channel over Ethernetdays that include Solid State Drives (SSD) that operate at (FCoE), which is gaining in popularity.close-to-memory speeds. For those only using an iSCSI SAN, basic EthernetObviously there is a price premium for SSDs, as well as switches may be enough. Some experts recommendFC disk. It’s a case of buying what your applications need dedicated switches for the iSCSI SAN rather than sharingand what you can get away with based upon your budget. them with the network. Others suggest server upgrades,Some arrays, after all, come with million-dollar plus price though, that is not always necessary.tags. But that level of functionality is rarely needed atevery business. Many disk arrays are attractively priced “For the majority of x86 servers, your existing 1Gbpsyet offer a decent amount of room for storage expansion. Ethernet gear is fast enough to use for iSCSI, too,”Features can vary greatly from one model to another. said Howard Marks, Founder and Chief Scientist at 6 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  8. 8. Data Storage InsightsHost Bus Adapters “Many of the arrays and switches used in large enterprises are designed to allow highly skilled storageHost bus adapters (HBAs) are necessary to connect the admins to tune them within an inch of their lives forSAN to the servers. Essentially, an HBA is a circuit board particular applications,” said Marks. “If you’re not alreadyor adapter that provides input/output processing and a crackerjack disk jockey you’re better off with a systemphysical connectivity between a server and the storage. designed to be easy to use and self tuning.”HBAs typically install into a PCI, PCIx or PCIe server slotor via a mezzanine card in a blade server with various He adds that the technology for self-tuning has improvedcombinations of ports, protocol supports and other to the point that today’s disk arrays are better at tuningfunctionality for security or management. Some HBAs are than 80 percent of the storage admins out there.for SAS, others for FC, iSCSI or on an increasing basesconverged network adapters (CNA) that support a mix Capacity vs. Performanceof FC, FCoE, iSCSI and NAS concurrently using a mix ofcopper and optical cabling. It is also essential to balance the SAN’s capabilities to your needs. Benjamin Woo, an analyst at IDC, says thatCabling an oft-used metric in storage purchasing — cost per gigabyte of storage capacity, is sometimes a “poorOptical transceivers as well as fiber optic, copper cabling metric.” He gives the example of System A having 20 TBor Ethernet cable is required to connect everything, of and costing $60,000 whereas System B with 30 TB costscourse. For more advanced environments, basic and the same price. System B with a lower price per TB wouldcomplex cable management systems are available to win the bid. But what about its number of Input/Outputsupplement basic cable tagging approaches. operations per second (IOPS), throughput, reliability and scalability? Going back to the example, he said that“Don’t skimp or try to save costs on your SAN by buying System A actually included Solid State Disks (SSDs) andcheap cables, and take care with them including keeping therefore has a much lower cost per IOP. Bottom line:connectors in good shape,” said Schulz. “One loose performance has to be taken into account as well asconnection, piece of dust or debris can render your SAN capacity. Those with no high-performance requirementin peril.” can afford to deal in cost per GB. Otherwise, application performance has to be factored in to the buying equationManagement Tools using metrics such as IOPS.Various SAN components come with their own “Performance is great if you need it and can use it,” saidmanagement tools, some of which provide configuration, Schulz. However if your applications cannot realize thediagnostics, reporting security and provisioning for other full potential due to software, server or other bottlenecks,components. you will not realize the benefits from a fast SAN.”Expertise and Experience Level More Buying TipsBut it isn’t just cables, tools and components. You have Marks said that once you reach the point where you areto know what you are doing. Those buying their first SAN spending $50,000 or more on a disk array, you shouldare typically not going to be experts in the technology be aware that there may be wiggle within the pricinginside. Therefore, it is important to understand that some structure.gear is meant for experts and others for beginners. Optfor the latter category. “There is a lot of negotiating room especially in the last 7 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  9. 9. Data Storage Insightsfew weeks of the vendor’s quarter,” said Marks.Another suggestion, he said, is to separate out thenice-to-haves from the vital by paying attention toimplementation timelines.“If you can’t get an approval from telecom for a WANlink for a year, don’t let the replication software drive thepurchase,” said Marks. “You might never get it running.”For those shopping for an FC SAN, though, pay closeattention to the Hardware Compatibility List (HCL), whichis typically issued by the disk array vendor. Any switches,HBAs and other gear have to be on the HCL. Therefore, itis usually best to begin with the array and work back fromthere in purchasing.Otherwise, Marks adds some advice for those whoalready have a SAN and are considering upgrades.“If you have an FC SAN, adding another array and stayingwith FC would be a smart idea,” said Marks.Keep in mind, though, that fast SANs need fast servers,fast servers need fast storage, fast storage needs fastnetworks and any speed bump or road block results inlost opportunity on your SAN investment. 8 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  10. 10. Data Storage Insights Why SANs Make Sense for Virtual Environments By Paul Rubens V irtualization technology offers many important area network, and applications like corporate databases business benefits, including lower capital also access larger files from the NAS from time to time. and facilities costs; greater flexibility; higher A typical NAS setup is perfectly suited to this type of availability; efficient backup capabilities; and environment where individual machines make single readseffective disaster recovery. For these reasons the majority or writes of data to and from the storage system on aof large enterprises have begun to virtualize at least regular basis, throughout the day.some of their IT infrastructure,and as the technology becomes But when you begin to introducemore mature and affordable, it is a virtualized server environmentbecoming increasingly attractive into your organization, demandsto growing businesses as well. on your storage systems can change dramatically. For smallerThat means that if you’re planning companies or those with a limitedto upgrade you storage systems, virtualized environment a typicalit makes sense to future-proof NAS device can continue toyour investment by ensuring provide a very effective and costthat anything you purchase will efficient storage solution, but asbe compatible with, and allow the business grows or in a largeryou to reap the full benefits of, virtualized environment a singlevirtualization. physical host can be sending out tens or even hundreds ofTo understand how the storage requests for data at any one time.requirements of virtual server What’s more, these requests willenvironments differ from those of occur on a highly random, rathertraditional server environments, than regular, basis. If you’ve gotlet’s take a closer look at a typical a number of physical hosts, each(non-virtualized) server setup. In small businesses servers supporting half a dozen or more virtual machines, thensimply make use of internal hard drives, and as storage this will place a heavy burden on your storage system. Yourequirements grow over time these are augmented by run the risk that the NAS device will turn into a bottleneckthe addition of direct attached storage (DAS) devices. and your local area network could struggle to cope withIf storage requirements increase further the next step is these bursts of storage traffic.commonly to upgrade to a shared storage system usingnetwork attached storage (NAS) or devices. That means that if you want to upgrade your storage systems to a solution that will enable you to get theIn a non-virtualized environment NAS solutions work well full benefits of virtualization as your company expands,because end users typically access small files such as a storage area network (SAN) may be a more suitabledocuments or spreadsheets from the NAS over the local option. That’s because a SAN has its own dedicated 9 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  11. 11. Data Storage Insightshigh bandwidth network for moving data to and from for business continuity and disaster recovery purposes.the physical computers hosting virtual machines— often In the event of a disaster the virtual machine files canbased on iSCSI in smaller SAN installations, and a SAN be run from new physical hosts at a secondary site ormay also be better suited to coping with the levels of data on machines rented from a business continuity servicerequests that a busy virtual server setup will throw at it. provider.Specific Benefits of Shared Storage in a Virtual Application AwarenessEnvironment Some SAN devices come with management software thatIn virtualized server environments, virtual machines exist enables application awareness in virtualized data files that run on physical hosts, but which can This is a technology that allows the storage systemactually be stored on a SAN or fast NAS. This opens up to recognize data from particular applications, and tothe possibility of using some sophisticated virtualization analyze the data’s usage patterns to optimize how andtechnology to bring you some valuable business benefits where that data is stored and backed up on SAS, SATA— if your storage system supports it. These include: or SSD disks. This can provide significant storage cost savings by matching data to the most appropriate storageInstant Failover media, and can also improve performance for some data- intensive applications significantly.Perhaps the most valuable benefit of employing aSAN (and, in some circumstances, NAS) in a virtualized SAN Softwareenvironment is the ability to have highly available virtualmachines that can continue to run without interruption, For companies with limited experience with virtualizedeven if the physical host running the virtual machine environments it makes sense to look for a SAN solutionfails unexpectedly. This technology is called vMotion in designed with virtualization in mind, and which comesa VMware virtualization environment and Live Migration with software that integrates with the major virtualizationin a Microsoft Hyper-V environment. In the event of a systems from VMware, Microsoft and Citrix. Doing soserver hardware failure the virtual machine file stored in ensures that the SAN will fully support the virtualizedyour SAN or NAS can be redirected to run on alternative server environment and make it easy to carry outhardware automatically without the need for the virtual functions such as uninterrupted failover, as well as datamachine to be stopped. protection, point in time data snapshots and functions, and transparent data migration between different storageBackup and Disaster Recovery devices.Another key benefit of using a SAN or NAS in a virtualized Scalabilityserver environment is the ease with which virtual machinescan be backed up or recovered in the event of a disaster. Many companies that introduce server virtualizationThat’s because, as mentioned above, virtual machines quickly discover that their storage capacity requirementsexist as a single virtual machine file stored in the storage grow very rapidly. There are a number of reasons for this,system. That means that individual virtual machines including a rapid expansion in virtualization once theor your entire virtual machine fleet can be backed up technology and benefits become better understood, andsimply by copying the appropriate virtual machine files the need to replace internal storage and DAS devicesacross the SAN or NAS, without any impact on local area with shared storage. For this reason it’s important tonetwork traffic. These files can also be copied to tape choose a storage solution, whether SAN or NAS-based,and physically moved off site, or copied over a wide that is easily scalable and which can be upgraded easily,area network link to another SAN at a remote location preferably without requiring periods of downtime. 10 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.
  12. 12. Data Storage InsightsSummaryGrowing businesses that aren’t yet taking advantage ofvirtualization can expect to be adopting virtualization inthe near future. In order to be prepared and to protecttheir storage investment, these businesses shouldconsider adopting a SAN to serve their virtual serverenvironments.SANs have an ability to provide disaster recovery, workaround hardware failures and scale to meet the needsof growing businesses that make them a worthwhileinvestment for businesses that need to adopt a newstorage infrastructure for their virtual environments. 11 Back to Contents Data Storage Insights: All About SANs © 2011,, a division of QuinStreet, Inc.