Hybrid Raid Whitepaper

HYBRID RAID WHITEPAPER

Adaptec Hybrid RAID Solutions

Combining SSDs and HDDs for Maximum Performance and Reliability

Introduction must fi rst be erased before new data can be written – even if only a few bytes are changed. Not only does this process negatively As user demand for speed grows and applications become more impact write performance, it can cause uneven wear on the surface and more robust, data centers face a constant battle to increase of the fl ash medium and lead to premature failure of the drive. their infrastructure performance accordingly. Some components off er a relatively straightforward upgrade path: CPUs continue To combat uneven wear, many SSDs employ wear leveling to to get more powerful, networking speeds increase, disk drive distribute erasures and rewrites evenly across the medium surface. capacities grow, and so on. But these advances mean little if the Wear leveling extends the life of the drive but, over time, also rate at which I/O operations can be performed doesn’t keep pace. further degrades write performance. For example, an online transaction processing system is oft en SSDs are also much more expensive than HDDs, especially when limited by the rate at which database updates can occur. Th e measured using the traditional “cost per GB of capacity” metric. performance of a search algorithm may depend on how quickly In most environments it is simply impractical to replace every various data structures can be read from disk. Th e number of users HDD with an SSD, regardless of the potential benefi ts. that can successfully access a website depends on how quickly the web pages can be served. However, a hybrid approach that combines HDDs and SSDs can be extremely cost eﬃ cient, especially when measured in terms of Growth in the number of end-users compounds the problem the “cost per I/O operation” or the more Green-oriented “power by cause longer response times and increasing latency. consumption per I/O operation”. According to Equation Research: 1 • 78% of site visitors have gone to a competitor’s site due What is Hybrid RAID? Approx. 400 IOPS / up to to 150 poor MB/s performance during peak times. 50% READ Hybrid RAID is a redundant storage solution that combines high-

Read performance on• SSD 88% are less likely to return to a site aft er a poor user capacity, low-cost SATA or higher-performance SAS HDDs with limited as 50% of all requests go to the HDD experience. low latency, high IOPs SSDs and an SSD-aware RAID adapter card (Figure 1). • 47% left with a less positive perception of the company. WRITE To boost system performance, data centers will sometimes add WRITE SATA or very fast hard disk drives (HDDs) — for example 15,000 RPM SAS drives Serial Attached SCSI (SAS) drives — and “short stroke” them, g 3 Approx. 400 IOPs / up to 150 MB/s 1. 50% whichREAD means that applications use only the outermost tracks on the disks where the performance is best. Or, they may add new servers, even if the existing servers have the storage capacity for RAID adapter SSD more users. Either method, however, results in low storage capacity utilization. On top of that, adding more servers leads to an increase in capital Figure 1. Hybrid RAID Deployment WRITE and operating expenses — namely maintenance, power and coolingWRITE costs — as well as physical space requirements. In Hybrid RAID, read operations are done from the faster SSD and write operations happen on both SSD and HDD for redundancy Th e proliferation of Solid State Drives (SSDs) alleviates many of Approx. 25K IOPs / up to 300 MB/s purposes. g 2 100%these READ problems, and is changing the way data centers think about their storage architecture. Hybrid RAID is ideal for applications with low levels of data, such as an Internet gateway, fi le server or virtual machine. SSDs: Performance in a Flash SSDs off er several advantages overFig 4HDDs, including higher read What Are the Beneﬁ ts of Hybrid RAID? bandwidth, higher IOPs, better mechanical reliability, and higher Hybrid RAID arrays off er tremendous performance gains over resistance to shock and vibrations. However, the same features (i.e., standard HDD RAID arrays at a much lower cost than SSD-only fl ash) that provide these advantages also come with some inherent 600 RAID arrays. Compared to HDD-only RAID arrays, Hybrid arrays limitations compared to HDDs, such as limited capacity and lower accelerate IOPs• and Adapter reduce card: latency, Adaptec allowing RAID 6805 data center and cloud streaming write bandwidth. 500 computing environments• Adapter card to Firmware: host more 18623 users and perform more Another limitation of SSDs is that they cannot directly overwrite transactions per• Windowssecond onDriver each Version: server, 18646 which reduces the number data like an HDD can. Instead, the entire destination data block of servers required• HDD to Hitachi support 3TB any SATA given HUA723020ALA640 workload. 400 • SSD: OCZ-Vertex3 MaxIOPS 1 “When more Website visitors hurt your business: Are you ready for peak tra c?,” Equation Research 2010 300

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• Adapter card: Adaptec RAID 6805 300 • Adapter card Firmware: 18623 • Windows Driver Version: 18646 250 • HDD Hitachi 3TB SATA HUA723020ALA640 • SSD: OCZ-Vertex3 MaxIOPS • AS SSD Benchmark v1.6.4237.30508 200

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Adaptec Hybrid RAID Solutions 2

Not only does the reduction in servers lead to reduced server 3. The unused disk space on each disk can be utilized in another footprint requirements within the data center, there is the array if required. additional financial benefit of reducing the capital expenses 4. In the above scenario, a 500GB RAID 5 disk could be created scenario 1 required to purchase additional servers, as well as the operatingscenario 1 across the six unused disk segments. scenario 2 scenario 3 scenario 4 scenario 5 expenses associated with power, cooling, and maintenance. Scenario 2: Workstation Hybrid RAID Examples 250GB 250GB 100GB In this scenario, the workstation Incorporating Hybrid RAID into a storage solution opens up a 600GB HDD HDD SSD user wants a fast-booting, fast 160GB 160GB 160GB wide range of possibilities for maximizing capacity, boot times, 300GB 500GB SSD SSD SSD SSD application-loading system and SSD HDD and overall performance, as shown in the following examples. 600GB doesn’t want the hassle of having RAID 1 SSD to rebuild the workstation if a drive Scenario 1: Large-Capacity Servers Usable capacity is 300GB fails. High-speed workstation 2TB In this scenario, the customer wants to make the maximum use HDD of space in a large capacity, 8-bay server, while still gaining a Figure 4. Workstation Hybrid RAID Solution System has two volumes fast-booting server. The customer is conservative and wants to 2 x 600GB mirror (high speed) 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDDkeep 3TBOS HDDaway from data (OS in mirror3TB and HDD data3TB in HDD RAID3TB 5HDD for 3TB HDDThe3TB HDDadvantages3TB HDD of3TB the HDD Hybrid solution (Figure 4) include: 3TB HDD 3TB HDD 3TB HDD 3TB HDD scenario 1 scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 RAID 5 maximum capacity). RAID 5 RAID 1 RAID 1 1. All reads are directed from the SSD, so read speed of the Usable storage capacity is 5 x 3TB hard drive (15TB) Usable capacity is 6 x 2.9TB (17.4TB) workstation is dramatically improved over that of a standard System has two volumes System has two volumes 250GB 250GB The server boots faster than the traditional server100GB 1 x 160GB mirror (high speed) 2 x 160GB mirror (high speed) HDD HDD SSD single HDD. 1 x 2.8TB mirror (high1 6capacity)0GB 1 x 2.186TB0GB mirror (high capacity) 160GB 600GB 300GB 500GB SSD SSD SSD SSD SSD HDD 2. Write speed is the same as a standard workstation, but due 600GB to the cache on the adapter card, it will be faster than a RAID 1 SSD Usable capacity is 300GB standard HDD connected to an on-board disk adapter. High-speed workstation 2TB HDD 3. Data is not lost if either drive fails. When the failed drive System has two volumes is replaced, the array will rebuild onto the replacement drive, 2 x 600GB mirror (high speed) 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD putting3TB HDD the3TB systemHDD 3TB HDDback3TB the HDD way3TB HDDit was3TB beforeHDD 3TB theHDD drive failure. 3TB HDD 3TB HDD 3TB HDD 3TB HDD RAID 5 RAID 5 RAID 1 RAID 1 Usable storage capacity is 5 x 3TB hard drive (15TB) Note thatUsable it capacity is not is 6 recommendedx 2.9TB (17.4TB) to use this unused 200GB System has two volumes System has two volumes The server boots faster than the traditional server 1 x 160GB mirror (high speed) 2 x 160GB mirror (high speed) capacity on the 500GB HDD due to the fact that this data is not 1 x 2.8TB mirror (high capacity) 1 x 2.8TB mirror (high capacity) Figure 2. Large-Capacity Server, Traditional HDD-Only Method redundant, and failure of the HDD would result in data loss.

The problem with an HDD-only method (Figure 2) is that it wastes Scenario 3: Small Business Server two bays in the server to the OS boot drives, and therefore limits capacity to six drives in RAID 5. Additionally, the server does not Many small business servers require at least some high- boot particularly quickly as it is booting from standard HDD in performance storage component to handle accounting software, scenario 1 mirror, which is not a particularlyscenario 1 fast form of RAID. industry-specificscenario 2 small databasesscenario 3 and even mail servers.scenario Along 4 scenario 5 with that performance is always the requirement for capacity. Even small business can easily generate several TB of data in 250GB 250GB scenario 1 100GB scenario 1 scenario 2 scenario 3 scenario 4 scenario 5 HDD HDD SSD the form of documents,160GB photos, video etc. 160GB 160GB 600GB 300GB 500GB SSD SSD SSD SSD SSD HDD 600GB RAID 1 SSD 250GB 250GB 100GB HDD HDD SSD Usable capacity is 300GB 160GB 160GB 160GB 600GB High-speed300GB workstation500GB SSD SSD SSD SSD SSD HDD 2TB HDD 600GB RAID 1 System has two volumes SSD 2 x 600GB mirror (high speed) Usable capacity is 300GB 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD High-speed workstation 2TB RAID 5 RAID 5 RAID 1 RAID 1 HDD Usable storage capacity is 5 x 3TB hard drive (15TB) Usable capacity is 6 x 2.9TB (17.4TB) System has two volumes System has two volumes System has two volumes The server boots faster than the traditional server 1 x 160GB mirror (high speed) 2 x 160GB mirror (high speed) 2 x 600GB mirror (high speed) 1 x 2.8TB mirror (high capacity) 1 x 2.8TB mirror (high capacity) 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD RAID 5 Figure 3. Large-CapacityRAID Server, 5 Hybrid RAID Solution RAID 1 RAID 1

Usable storage capacity is 5 x 3TB hard drive (15TB) Usable capacity is 6 x 2.9TB (17.4TB) System has two volumes System has two volumes The HybridThe server solution boots faster (Figurethan the traditional 3) offersserver several benefits: 1 x 160GB mirror (high speed) 2 x 160GB mirror (high speed) 1 x 2.8TB mirror (high capacity) 1 x 2.8TB mirror (high capacity) 1. Total server capacity is six times the usable capacity of each drive in a RAID 5. Figure 5. Small Business Server, Hybrid RAID Solution

2. The server will boot quickly as it is reading from an SSD during the boot process HYBRID RAID WHITEPAPER

Adaptec Hybrid RAID Solutions 3 scenario 1 scenario 1 scenario 2 scenario 3 scenario 4 scenario 5

The advantages of this Hybrid solution are: 250GB 250GB 100GB 1. The 160GB disk is big enough to create a boot volume for 600GB HDD HDD SSD the OS while16 0stillGB leaving enough space for a 100GB160GB volume 160GB 300GB 500GB SSD SSD SSD SSD SSD HDD for database function. 600GB RAID 1 2. Because the 160GB hybrid mirror reads directly from the SSD Usable capacity is 300GB SSD, both OS boot time and database function will be High-speed workstation greatly improved over a standard mirror of two HDDs. 2TB HDD 160GB is lost from the capacity of the data mirror, but that is a System has two volumes small percentage of capacity loss on the 3TB drives, and does not 2 x 600GB mirror (high speed) 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD significantly impact on the usable capacity of the server. Figure 7. Small Business Server, High-Speed, Small Capacity RAID 5 RAID 5 RAID 1 RAID 1 Hybrid RAID Solution Scenario 4: Small Business Server Usable storage capacity is 5 x 3TB hard drive (15TB) Usable capacity is 6 x 2.9TB (17.4TB) System has two volumes System has two volumes The server boots faster than the traditional server The previous configuration1 x 160GB mirror requires (high speed) at least a 4-port RAID2 x 16 0card,GB mirror (highNote speed) that it would be possible in this configuration to add a third 1 x 2.8TB mirror (high capacity) 1 x 2.8TB mirror (high capacity) but the fourth port is unused. Extending the server to utilize all SSD (using the fourth port on the RAID card), to give three hybrid four ports is simply a matter of purchasing a second 160GB SSD mirrors on a total of three SSDs and one HDD. scenario 1 scenario 1 scenario 2 scenarioto mirror 3 to the unused spacescenario from the4 previous example.scenario 5 Building a Hybrid Solution From a hardware perspective, building a Hybrid RAID solution is 250GB 250GB 100GB HDD HDD SSD 160GB 160GB 160GB 600GB fairly straightforward as any capacity of SSDs and HDDs can be 300GB 500GB SSD SSD SSD SSD SSD HDD used (though an equal number of SSDs and HDDs must be used). 600GB RAID 1 SSD If the RAID array is built from different-sized drives, the drive Usable capacity is 300GB segment size is the size of the smaller disk drive. For example, High-speed workstation 2TB a RAID 1 created with one 128GB SSD and one 2TB HDD will HDD System has two volumes make a 128GB logical device. A RAID 10 created with two 2 x 600GB mirror (high speed) 128GB SSDs and two 2TB HDDs will make a 256GB logical 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD 3TB HDD device. The remaining HDD capacity can be used for storage. RAID 5 RAID 5 RAID 1 RAID 1 From an application perspective, though, it’s not quite as simple Usable storage capacity is 5 x 3TB hard drive (15TB) Usable capacity is 6 x 2.9TB (17.4TB) System has two volumes System has two volumes The server boots faster than the traditional server 1 x 160GB mirror (high speed) 2 x 160GB mirror (high speed) since most software was not created to be aware of the possibility 1 x 2.8TB mirror (high capacity) 1 x 2.8TB mirror (high capacity) of having two types of storage with such different characteristics. Figure 6. Small Business Server, Hybrid RAID Solution In order to take full advantage of a Hybrid RAID setup, an SSD- aware RAID adapter with intelligent storage processing must It might seem more sensible to mirror the two SSDs, and then be deployed. mirror the two HDDs in what would seem a more conventional server. However, there is good reason to do the above: Adaptec Hybrid RAID Solutions 1. The write speed of lower-spec SSDs is not much faster than Fortunately, reaping the rewards of Hybrid RAID technology that of HDDs, so there is little to be gained by mirroring the can be as simple as installing updated firmware onto any two SSDs. Adaptec Series 7, Series 6, or Series Q SAS/SATA RAID adapter. 2. Since the read speed of the SSD is so quick, putting them in a The adapter takes care of the rest by automatically creating a mirror will not result in much improvement over a single SSD. Hybrid RAID array whenever one or more SSDs are combined with the same number of HDDs in a RAID 1 or RAID 10 array. 3. Since the focus is on read speed, having two Hybrid RAID The Hybrid RAID is completely transparent to the operating arrays now gives 320GB of SSD read speed to the server, while system and all running applications. still protecting the data on each SSD in the form of a mirror. 4. The HDD capacity of the server is not sacrificed from the Additionally, Adaptec RAID adapters deliver maximum Hybrid previous example. array performance by writing to both HDD and SSD, and reading from SSD 100% of the time (Figure 8). By contrast, other adapters Scenario 5: Small Business Server, High-Speed, Small Capacity write and read from HDD and SSD (Figure 9). Since server I/O If performance is more important than capacity, then the user can of an SSD can be up to 100 times faster than HDD, competitive install two 600GB SSDs and mirror them to the HDD, thus gaining Hybrid RAID solutions typically deliver lower I/O performance. 1.2TB of SSD capacity (Figure 7). Approx. 400 IOPS / up to 150 MB/s 50% READ

Read performance on SSD limited as 50% of all requests go to the HDD

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Read performance on SSD • Adapter card: Adaptec RAID 6805 limited as 50% of all requests 500 • Adapter card Firmware: 18623 go to the HDD • Windows Driver Version: 18646 • HDD Hitachi 3TB SATA HUA723020ALA640 400 • SSD: OCZ-Vertex3 MaxIOPS WRITE 300 WRITE HDD 200 HYBRID RAID WHITEPAPERSSD Approx. 400 IOPs / up to 150 MB/s Hybrid 50% READ 100

Adaptec Hybrid RAID Solutions 0 4 100% Seq. 100% Seq. 100% Ran. 100% Ran. Read 512K Write 512K Read 512K Write 512K

Some applications even see a slight performance benefi t from Adaptec Hybrid RAID and are faster on a Hybrid RAID 1 than Fig 5 on a single SSD (Figure 11). WRITE

WRITE • Adapter card: Adaptec RAID 6805 300 • Adapter card Firmware: 18623 • Windows Driver Version: 18646 250 • HDD Hitachi 3TB SATA HUA723020ALA640 Approx. 25K IOPs / up to 300 MB/s • SSD: OCZ-Vertex3 MaxIOPS 100% READ • AS SSD Benchmark v1.6.4237.30508 200

Figure 8. Adaptec Hybrid RAID Solution 150

HDD 100 SSD Approx. 400 IOPS / up to 150 MB/s Hybrid Approx. 400 IOPS / up to 150 MB/s 50% READ 50% READ 50 Read performance on SSD Read performance on SSD limited as 50% of all requests go to the HDD limited as 50% of all requests go to the HDD 0 ISO Image Applications Games WRITE Processing WRITE SATA or WRITE SAS drives Figure 11. AS SSD Application Performance g 3 Approx. 400 IOPs / up to 150 MB/s 1. 50% READ WRITE SATA or SAS drives RAID adapter SSD As such, Adaptec Hybrid RAID off ers better performance and Approx. 400 IOPs / up to 150 MB/s lower cost/GB, and lower cost and power consumption per I/O g 3 1. 50% READ than competing Hybrid RAID solutions. WRITE

WRITE Figure 9. Competitive Hybrid RAID Solution RAID adapter SSD Approx. 25K IOPs / up to 300 MB/s Conclusion g 2 100% READ Adaptec Hybrid RAID arrays deliver a higher number of read Data centers face never-ending pressure to accommodate operations per second than standard HDD arrays with no more users and more traﬃ c. In the face of tightening degradationFig 4 of write I/O performance (Figure 10). budgets, however, the days of simply adding more servers WRITE are coming to an end. 600 WRITE Hybrid RAID arrays of SSDs and HDDs off er signifi cantly • Adapter card: Adaptec RAID 6805 better performance than standard HDD RAID arrays at 500 • Adapter card Firmware: 18623 a lower cost than SSD-only arrays. Approx. 25K IOPs / up to 300 MB/s• Windows Driver Version: 18646 g 2 100% READ • HDD Hitachi 3TB SATA HUA723020ALA640 400 Adaptec Series 7, Series 6, and Series Q SAS/SATA RAID • SSD: OCZ-Vertex3 MaxIOPS adapters with the latest fi rmware updates can automatic- 300 ally create a seamless Hybrid RAID array whenever one

HDD or more SSDs are combined with the same number of 200 HDDs in a RAID 1 or RAID 10 array. Unlike competing SSD Fig 4 Hybrid RAID adapter cards that read from the HDD 50% of the 100 time, Adaptec cards deliver maximum system performance by reading only from the SSD. 0 100% Seq. 100% Seq. 100% Ran. 100% Ran. Read 512K Write 512K Read 512K Write 512K 600 Compared to HDD-only arrays, Adaptec Hybrid arrays deliver a higher number of read operations per second with no degradation of write I/O performance, and • Adapter card: Adaptec RAID 6805 Figure 10. IOMeter Raw Performance 500 Fig 5 complete transparency to the operating system and all • Adapter card Firmware: 18623 running applications. Compared to SDD-only arrays, • Windows Driver Version: 18646 Adaptec Hybrid arrays off er the lowest cost/GB and • HDD Hitachi 3TB SATA HUA723020ALA640 • Adapter card: Adaptec RAID400 6805 lowest cost and power consumption per I/O. 300 • Adapter card Firmware: 18623 • SSD: OCZ-Vertex3 MaxIOPS PMC-Sierra, Inc. • Windows Driver Version: 18646 2501380 Bordeaux Dr. World Wide Web: www.adaptec.com• HDD Hitachi 3TB SATA HUA723020ALA640 Sunnyvale, CA 94089 USA Pre-Sales Support: US• SSD: and OCZ-Vertex3Canada: 1 (800)MaxIOPS 442-7274300 or (408) 957-7274 or [email protected] Tel: +1 (408) 239-8000 UK:• AS +44 SSD 1276 Benchmark 854 528 v1.6.4237.30508 or [email protected] 200 Australia: +61-2-90116787 Singapore: +65-92351044 HDD 150© Copyright PMC-Sierra, Inc. 2012. All rights reserved. PMC, PMC-SIERRA and Adaptec are registered trademarks of PMC-Sierra, Inc. “Adaptec by PMC” is a trademark of PMC-Sierra, Inc. Other product and company names mentioned herein may be trademarks of their respective owners.200 For a complete list of PMC-Sierra trademarks, see www.pmc-sierra.com/legal. HDD SSD WP_HYBRIDRAID_081912_US Information subject to change without notice. 100 SSD Hybrid Hybrid 50 100

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