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Coffee break


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Coffee break

  1. 1. TECHNICAL BULLETIN / COFFEE BREAK SOLID STATE DISKS AND STORAGE TIERING A NEW DISK TIER Standard hard disk drives (HDDs) are spinning disks, and their mechanical actions can create a delay in data retrieval. Solid-state disks (SSDs) are an exciting improvement in disk technology - made of silicon memory chips and with no moving parts, SSDs have no rotational delay and near zero seek time, dramatically reducing response times. SSDs can be extremely valuable to applications that need fast performance. SSDs offer a high-performance storage tier commonly referred to as Tier 0. If storage administrators know The solid-state disk market of data that will be in high demand, they can place it on SSD for fast performance, and place other data on is growing as automated HDD tiers. Since the effectiveness of SSD as a disk tier storage tiering takes hold, but is based solely on how well the administrator can place it remains difficult for IT to data, it remains a solution that is useful for IT shops with determine which applications a known performance problem on specific data sets. can benefit from SSD tiers. Most IT organizations are still unsure of whether SSDs can help them cost effectively. THE NEXT EVOLUTION: AUTOMATIC TIERING Recently, however, storage vendors have begun offering automated tiering along with better storage controller integration. Arrays can use SSDs dynamically, in concept like a dramatically larger cache. Instead of fully populating an enclosure with SSD drives, only a few SSDs are included; intelligent load-balancing algorithms identify “hot” data sets and move them to the SSD tier. When the data sets are . . . And then Solid State Disk no longer “hot,” they are moved back Hot data is returned to HDD to a slower tier. Organizations can moved to SSD. . . when no longer hot. use fewer SSDs, and use them more efficiently. This type of automated deployment can spread SSD usage across more data and applications, Hard Disk Drives eliminate the manual task of assigning data to an SSD tier, and reduce costs.
  2. 2. HOW DO I KNOW IF IT’S FOR ME? Because SSD storage is expensive, organizations want to be sure of its benefits before making an investment. Solutions that require administrators to manually track and move data offer fewer SIMPLIFY YOUR STORAGE AT WWW.DELL.COM/PSSERIES benefits than those that monitor and move data automatically. In addition, it is difficult to know which workloads need this class of performance, and whether the benefit is worth the cost. Will SSD implementation improve an application’s performance, or can that application achieve only a certain performance level no matter what disk type it uses? These answers are hard to ascertain and often the only way to find out is to try a different disk and see what happens.Knowing your workload characteristics will help you determine whether SSDs can help - unfortunately, these characteristics are not easy to distinguish. IDENTIFYING TIER-ABLE WORKLOADS Best practices designed to alleviate Automatic load balancing with SSDs can hotspots may be at cross purposes with improve performance as long as the active automated storage tiering with SSD, and data set fits in the SSD storage, but currently may change in the future. there are no tools in operating systems or performance and streamline storage costs. storage arrays to identify active data set size. Without hotspots, administrators may be Storage arrays offer performance statistics, forced to place all of an application’s data on but that data describes only what happened high-performance disks to ensure for an entire LUN. Plus, there is no way to high performance. With hotspots, estimate how workload characteristics would they may configure a small amount of change on a different storage medium. We high-performance SSD for some data, and can see where the storage system is busy, and less costly HDD and RAID types for the we can see whether the application is waiting rest. The growth of SSD in the data center or not, but we cannot predict how much faster will alter many best deployment practices. an application might perform with improved storage performance. These practicalities will EVALUATING TIERED STORAGE SOLUTIONS be ironed out over time as the use of these For known tier-able workloads, SSDs are a technologies matures in operating systems, great advancement. This popular and growing applications, and storage devices. technology is more widely applicable with SOME ARE, SOME AREN’T automated storage tiering. When considering these solutions, be sure you know what you Since data access hotspots make tiering are getting. What processes are automated beneficial, workloads with hotspots are more - selection of data to move, actual data appropriate for SSD tiering than those without. movement, or both? Is data movement only For example, in virtual desktop infrastructures, at the LUN level, or can more granular hot a master image is created from which many spots be accommodated? Does automated desktops boot. When many desktops boot tiering impact or limit other advanced simultaneously, they work that image very hard functions such as snapshots and replication, — this is a naturally tier-able workload that is and do these data copies automatically easy to identify because you know how it will move to the slower, less expensive tiers? be used. Many databases are also prone to hot spots. SSDs offer significant benefits if they fit SSD TIERS IMPACT APPLICATION your workloads. However, if your workloads DEVELOPMENT AND DEPLOYMENT do not require high performance or are not The ability of automated SSD tiers to handle tier-able, an investment in SSD’s may not data hotspots will impact application be cost-efficient. While your system may development and deployment. To optimize perform well, it could be over-provisioned and performance, developers and administrators under utilized for what the applications can follow best practices designed to minimize leverage. As these technologies mature, more or avoid hotspot creation. These traditional information should become available to help best practices may not be appropriate administrators know exactly which data sets when intelligent, automatic tiering is will benefit from SSDs and automated tiering. available. Because of automated tiering and SSDs, hotspots can be used to improve © 2010 Dell Inc. CB132_030310