Product Analysis of AssuredSAN 4000 with RealStor
The world has changed for IT. Social media, the internet of things, the proliferation of mobile devices, etc, are creating the challenge of real-time computing. Processing power has become plentiful and virtualization has made it easier to build the infrastructures needed to handle all this real-time data. But some things haven’t changed. For the most part, storage is still the bottleneck.
To keep up the storage industry has turned to flash to provide massive amounts of performance, especially IOPS. While the cost of flash is decreasing and all-flash arrays are becoming more common, hybrid arrays are still the simplest way to balance the real-time performance IT needs with large capacity requirements. This is exactly why long-time storage system manufacturer Dot Hill designed the AssuredSAN** 4000 Series with RealStor**.
Real-time Hybrid Arrays
Hybrid storage systems leverage flash and large hard disk tiers to improve overall cost per GB and enable them to provide much more capacity than all-flash arrays can. But traditional ‘first generation’ hybrid systems often struggle with how they write data, how they move it between tiers and how they handle the storage CPU overhead generated by these processes, resulting in issues with performance and efficiency.
Next-generation hybrid arrays use a real-time tiering process to ensure that the right data is in flash when it’s needed and leverage a CPU-friendly architecture to move data efficiently without impact to storage performance. Maintaining performance with high availability in the face of this continual data movement is also a requirement.
RealStor 2.0
RealStor 2.0 is the second generation of Dot Hill’s storage operating system driving the performance and efficiency of their AssuredSAN 4004 hardware platform. RealStor is comprised of several different features including: RealTier**, (real-time autonomic tiering) and RealCache** (read caching) leverage solid-state drive (SSD) and hard disk drive (HDD) storage areas, plus advanced features like RealQuick** (rapid RAID rebuild), RealSnap** (virtualized snapshots) and RealThin** (thin provisioning).
What is “Real-time, Autonomic” Data Tiering?
The tiering process in RealStor’s RealTier feature consists of analyzing data access characteristics, ‘scoring’ each data object to determine the appropriate tier for that data, and then moving it. Originally, many hybrid storage systems used a batch process to do this analysis and movement after hours. These systems leveraged this approach because tiering consumed storage system resources like CPU cycles and network bandwidth. As a result the analysis and movement of data could degrade storage performance. Many of these systems also wrote first to the hard disk tier because of concerns about flash wear and then promoted data to flash during the next movement cycle.
The problem with this technique is that it moved data based on what was often old information. As Storage Switzerland Founder, George Crump, discusses in the article, “Storage for the Real-time Data Center”, this can be like batch delivery of newspapers, not a very effective process. The result can be less efficient tiering and inconsistent performance.
Dot Hill’s RealTier effectively runs this tiering process continuously, scanning, scoring and moving data every 5 seconds. To minimize performance impact on the system it throttles the amount of data traffic created by these move operations to 80MB every second. The Dot Hill storage system also has additional processing power to handle this extra load. It uses a custom-designed ASIC (Application-Specific Integrated Circuit) to process all I/O traffic to the host, perform RAID functions, and manage cache coherency for both controllers. This architecture enables real-time autonomic tiering with minimal CPU overhead from the storage controllers, ensuring consistent host performance.
RealTier supports three storage areas, an SSD tier, a SAS disk tier and a nearline disk tier. Besides moving data between the flash and disk tiers, it can move data between performance and capacity HDD tiers as well. RealStor also provides a read cache function called RealCache. RealCache helps maximize application read performance and has the ability to assign a preference for specific volumes to access flash to support the most critical workloads.
It can also bypass the flash tier altogether and write directly to disk drives, a feature that’s useful in streaming media applications to eliminate needless flash write activity, improve flash efficiency and increase flash endurance.
Storage Efficiency
RealStor includes RealSnap virtualized snapshots, a redirect-on-write process that supports up to 1024 snapshots at a time without impacting storage performance. Users can set up snapshots for multiple volumes simultaneously using the Storage Management Console. RealThin is the system’s thin provisioning technology that eliminates storage over-allocation, enabling more efficient volume management and non-disruptive capacity expansion.
Using RealThin thinly provisioned volumes, users gain capacity efficiency with modern file systems (ie. Microsoft Windows NTFS) which return unused space back to a common pool of storage when users delete files/directories. In addition these volumes are scanned for any zero-block allocations and are automatically compressed for maximum space efficiency.
Rapid RAID Rebuilds
In this era of multi-TB disk drives a RAID rebuild can take hours, or days. Obviously, this can be a problem for hard drive-based and hybrid primary storage arrays, especially in an environment that is expecting real-time workloads and flash-based performance. RealStor’s RealQuick technology helps address this by only rebuilding sectors that contain data, skipping the “white space” that represents the unused areas of a disk drive. The result is up to 5x faster rebuild performance over traditional RAID technologies (depending on the capacity utilization of the disks).
AssuredSAN 4004
AssuredSAN 4004
The AssuredSAN 4004 is an 8-port, fibre channel-, iSCSI- and SAS-connected storage array that supports SSDs, SAS and near-line SAS HDDs. The system scales up to a maximum of 224 LFF drives in four 4U56 chasses or 192 SFF drives in four 2U48 chasses.
Designed for high-performance workloads, it provides 6400 MB/s sequential reads and 5300 MB/s sequential writes with 120,000 IOPS from disk. AssuredSAN has dual RAID controllers supporting RAID 0,1,3,5, 6,10 and 50, with redundant, hot-swap components for maximum uptime.
Dot Hill offers self-encrypting hard disk drives that encrypt data as it’s being written to the drive and decrypt with each read cycle, providing data security without requiring authentication keys from the owner. They also provide instant data destruction via cryptographic erase and are available in 1.2TB 2.5” and 4TB 3.5” hard drive form-factors.
Energy Saving Design
The AssuredSAN 4004 features Dot Hill’s EcoStor** technology that uses supercapacitors and compact flash instead of batteries to maintain cache data integrity during a power loss. These arrays can also spin down disk drives to save power. This allows users to create energy-efficient tiers for use cases that need longer data retention without taking data off of the array. Dot Hill AssuredSAN 4004 arrays are also ENERGY STAR qualified based on certification testing to the United States Environmental Protection Agency standards.
StorageSwiss Take
Flash has become the accepted technology for adding performance to a storage system. For many environments hybrid storage arrays that include both flash and hard disk drives are the preferred solution because they deliver a performance improvement while keeping costs under control. But legacy hybrid arrays can have trouble keeping up with the real-time workloads that are increasingly common in data centers of all sizes. It simply takes too long for the hybrid array to adapt to the changing workload.
Real-time hybrid array technologies can address this problem by processing and moving data objects between flash and disk tiers on a virtually continual basis. This assures that the right data is on flash when it’s needed and then moved quickly to capacity disk storage as soon as possible.
Systems like DotHill’s AssuredSAN 4004 with RealStor 2.0 software can perform real-time tiering without impact to storage performance, providing the economics of hybrid storage while eliminating the storage bottleneck in a real-time data center.
Sponsored by Dot Hill
** AssuredSAN, RealStor, RealCache, RealQuick, RealSnap, RealThin and EcoStor are trademarks or registered trademarks of DotHill
George Crump is the Chief Marketing Officer at VergeIO, the leader in Ultraconverged Infrastructure. Prior to VergeIO he was Chief Product Strategist at StorONE. Before assuming roles with innovative technology vendors, George spent almost 14 years as the founder and lead analyst at Storage Switzerland. In his spare time, he continues to write blogs on Storage Switzerland to educate IT professionals on all aspects of data center storage. He is the primary contributor to Storage Switzerland and is a heavily sought-after public speaker. With over 30 years of experience designing storage solutions for data centers across the US, he has seen the birth of such technologies as RAID, NAS, SAN, Virtualization, Cloud, and Enterprise Flash. Before founding Storage Switzerland, he was CTO at one of the nation's largest storage integrators, where he was in charge of technology testing, integration, and product selection.
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