Call it growth, scaling, or expansion – whatever you call it, increasing your storage resources often strikes fear and loathing in the heart of the IT administrator. It conjures up visions of downtime, extra management tasks, frustrated users, and working nights and weekends. In addition, since capacity and performance are intimately connected, increasing storage resources can require balancing changes that affects the entire the SAN.
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IMPROVING STORAGE EXPANSION FOR SERVERS AND APPLICATIONs
A solution that can scale Call it growth, scaling, or expansion - whatever you call it, increasing your storagestorage completely - online, resources often strikes fear and loathing in the heart of the IT administrator. It conjures upwithout downtime or disruption visions of downtime, extra management tasks, frustrated users, and working nights and- makes growth painless weekends. In addition, since capacity and performance are intimately connected, increas-and eliminates the need for ing storage resources can require balancing changes that affects the entire the SAN.over-provisioning. THE PAIN OF EXPANDINGThe challenges of expansion stem from multiple factors - in particular, your storagearchitecture, hardware, operating system, applications, and operational requirements.For example, when adding a disk in a direct-attached storage (DAS) configuration, thefirst step is to get a screwdriver - which means you must shut down applications andturn off the system (assuming there are slots for additional storage available). Once youhave added the new disk, the applications are still using the original storage, so youneed to stop the applications, copy and divide the data manually between drives, recon-figure the application so it is aware of the changes, and then re-start. This process isdisruptive and time consuming - and as a result, many IT shops over-provision storageup front in hopes of avoiding the expansion process altogether. This plan costs moneyand wastes resources, but many IT managers find it the lesser of two evils.
In a storage area network (SAN), expansion is only slightly easier - at least it takes thescrewdriver out of your hand. However, you are commonly still forced into offline copying and balancing operations.
Expanding your storage can also create performance bottlenecks. After addingdisks, will the controllers be able to handle the additional throughput? Will yourcache handle the extra capacity? What about SAN bandwidth into the storagearrays? Have you added network links? With most solutions, no additional controllers, cache, or network links are added, so these components becomeover-burdened and require re-balancing. The result: performance suffers.EXPANSION FOR NEW AND EXISTING APPLICATIONS scale infrastructure, you want more of everything - capacity, There are two general reasons for expanding your storage performance, and bandwidth - but you don't want more work.capacity. First, you may expand when your current system isrunning well but you want to add storage to support new SOLUTION: SHIFT THE WORK TO THE STORAGE SYSTEMapplications. In this scenario, you may not have to shut exist- What administrators really need is more capability than ising applications down and reconfigure - you can just add the offered by most SAN vendors. Vendors may say that you canstorage and deploy the new application. However, as men- add storage and placetioned before, additional storage places additional burden on it into production QUALIFYING QUESTIONS FOR STORAGE EXPANSIONyour controllers, cache, and online, while onlySelect the storage solution and network links, so re-balancing meaning that disks Can all resources be expanded online,operating system that offer you is required because of these can be added to a without downtime or disruption?the most functionality and least shared resources - causing cabinet - rather than Is the process of expanding storagedisruption, whether you are planned downtime and after- put into expanded and resources and putting it into use complet-adding storage for existing ed online, or will some management taskshours administrative tasks. balanced application need to be completed offline?applications or new ones. use - online. UnlessThe second scenario is when you ask probing ques- When adding disk drives, are controllers,capacity, and network links also scaled?you want to add resources to existing applications to improve tions this distinctionperformance or increase capacity. Because applications are may not be apparent. When adding capacity, how will perform-ance be affected for existing applications?running, online vs. offline expansion and re-configurationbecomes critical. The ability to add disks online is helpful, but With EqualLogic PS In a SAN, will each ... [download for more]
