IBM Easy Tier Enables DS8700 Users to Make Good Use of Solid State Drives


Published on

IBM DS8700 users now have the tools in Easy Tier and its associated software tool Storage Tier Advisor to evaluate the benefits of, plan for, deploy, and manage on an ongoing basis SSDs in combination with existing HDDs. It’s not for nothing that IBM calls its product Easy Tier.

Published in: Technology
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

IBM Easy Tier Enables DS8700 Users to Make Good Use of Solid State Drives

  1. 1. Mesabi GroupCommentary April 12, 2010 IBM Easy Tier Enables DS8700 Users to Make Good Use of Solid State Drives Solid state drives (SSDs) are a hot topic of interest in IT organizations because of their potential to turbocharge storage performance. One inhibitor to adoption has been the high cost of SSDs relative to hard disk drives (HDDs) and a second has been the problem of when and how to use SSDs efficiently and effectively. IBM DS8700 users now have the tools in Easy Tier and its as- sociated software tool Storage Tier Advisor to evaluate the benefits of, plan for, deploy, and manage on an ongoing basis SSDs in combination with existing HDDs. It’s not for nothing that IBM calls its product Easy Tier. they can justify an investment in SSDs.The Promise of Solid State Drives And that means getting just the rightFlash-memory-based solid state drives amount of SSDs as a blend with HDDs,(SSDs) offer a storage Tier 0 comple- to avoid over-provisioning the morement to Tier 1 Fibre Channel (FC) costly SSDs.drives in an enterprise-class diskarray. SSDs promise: IBM’s System Storage DS8700 users now have the tools — with the combi-• Opening up additional revenue nation of Storage Tier Advisor and Easy possibilities by increasing the Tier — to be able to plan for and use transactions per second or by re- SSDs appropriately in their distinctive ducing elapsed time of now- workload environments. The Storage performance-bound revenue- Tier Advisor software tool offers generating applications. guidance to users on how existing• Saving money by reducing hard- workloads can benefit by moving ware resources, since there is less certain data to SSDs. Easy Tier, free need for data to be duplicated firmware functionality in a DS8700 across disks in order to reduce I/O system, is the operational tool that wait time. manages the proper placement of dataThese benefits are potentially alluring between SSDs and HDDs on ato IT organizations. However, because continuous basis. Its continuousof the much higher relative cost of workload monitoring capabilitySSDs as compared to traditional hard dynamically determines whether or notdisk drives (HDDs), cost-conscious IT data should be on an SSD or an HDD,organizations have to make sure that and, as necessary, automatically moves© 2010 Mesabi Group LLC Telephone: 781 326 003826 Country Lane Fax: 781 326 0038Westwood, Massachusetts 02090
  2. 2. Easy Tier Enables DS8700 Users to Make Good Use of Solid State DrivesCommentary Page 2data non-disruptively from one tier to short stroking is used, SSDs may verythe other. well offer a cost-justified alternative.Before examining IBM’s solution, anunderstanding of HDD performance SSDs Overcome HDD Performanceissues and how SSD solves them — but Problems, but at a Priceat a price — is necessary. Non-volatile semiconductor (NAND flash) chips are embedded in an SSDThe Trouble with HDD Performance drive that has the same traditionalThe fastest HDD drives have been form factor as an HDD. The SSDstuck at 15,000 rpm for some time now appears to a disk storage system (andand, for technical reasons, are likely to to the server) as a random access HDD.stay more or less that way. Processor Reliability is no longer an issue withcapabilities have not been similarly today’s enterprise-class SSDs, so ourconstrained. The result is that, despite discussion focuses on price andthe continued shrinkage in disk space per datum, the perform- SSD drives are available in 73 and 146ance gap between processors and the GB capacities versus 73, 146, 300,fastest HDDs is growing. 450, and 600 GB capacities for theThis widening performance gap leads to highest-speed HDDs on the increased I/O wait time, which is The rough tale of the tape (Table 1)the time that a CPU spends waiting for shows that SSDs are an order ofdata from a storage system. Not only is magnitude more expensive for thethat a problem with single OS-based same capacity than an HDD. However,physical servers, but the problem may SSDs are much faster than HDDs andbe compounded when multiple virtual the result is that the SSDs aremachines (VMs) all want to access dramatically cheaper for each (However, note that performancedelays will not scale linearly with the Table 1: Enterprise-Class Comparisonnumber of VMs, because a disk arraycan service multiple VMs more or less Between SSDs and HDDsin parallel.) Having expensive serversunnecessarily idle is an investment Measure SSDs vs. HDDswaste to which the proper use of SSDs Relative Cost 10:1offer a possible solution. RatioOne HDD workaround to increase disk Input/Outputs Thousands to tens ofperformance is short stroking. In short Per Second thousands vs. tens tostroking, only the outside tracks on an (IOPS) possibly hundredsHDD have data. This significantlyreduces the access seek time for a IOPS/$ 20:1disk’s head to find a requested track. Source: Objective Analysis April 2010The downside is that much of thedisk’s capacity is not used and many This comparison highlights relativemore disks have to be used. When differences, which are important when a lot of money is involved. A formal cost© 2010 Mesabi Group LLC Telephone: 781 326 003826 Country Lane Fax: 781 326 0038Westwood, Massachusetts 02090
  3. 3. Easy Tier Enables DS8700 Users to Make Good Use of Solid State DrivesCommentary Page 3analysis — involving the use of disks, Naturally, an analysis has to bethe I/O wait impact upon servers, and conducted initially to determinepower (SSDs are more efficient) — may whether or not using one or more SSDsalso need to be done. makes sense. If one or more SSDs areBut costs can also be viewed as inserted into a storage array configura-absolute, i.e., viewed independently tion, then all three functions workand not in a comparative or relative together in an iterative and continuoussense. Here absolute costs mean the fashion.actual out-of pocket-costs, and tell uswhether a solution is affordable at all. Getting the Right Balance Between SSDsAnd with the fast decline in SSD and HDDsprices, quite frankly even the starting Before the amount of SSD capacity canpoint of a mini-pack of 8 drives may be determined for a given workload andnot be out of reach economically with put to correct use with the right data,even a simple cost analysis. some “rule of thumb” and “best practice” approaches can always beStarting small and trying SSDs gives applied to guesstimate based onreal-world experience that can give application performance characteristicsmore information as to whether further observed and the understanding ofSSDs can be justified. And Easy Tier storage system architecture. To(along with the Storage Tier Advisor) improve the accuracy and predictionenables planning and managing SSDs process, information has to be collectedin the most cost efficient manner, on that shows what data could benefit byan ongoing basis, to complement the being moved to SSDs. Only then can ause of HDDs. determination be made to acquire SSDs as well as to put in place anEasy Tier’s Basic Capabilities ongoing data monitoring and migra-The combination of Easy Tier and the tion. And it all starts with the analysisStorage Tier Advisor performs the of existing data via a “heat map.”following three basic functions:• Workload hotspot analysis — Heat Mapping reports can provide information on The critical construct for being able to data access patterns that can pro- determine what data is best suited to vide SSD capacity planning recom- which tier is called a “heat” map. Of mendations. course, all the allusions to “heat,”• Continuous workload monitoring — “temperature.” “hot,” and “cold” are this dynamically determines metaphors that relate to the frequency whether data on the HDD tier needs of access patterns to different sets of to be promoted to the SSD tier or data rather than the typical physical whether data on the SSD needs to interpretation of those words. be demoted to the HDD tier. Candidates for movement to an SSD• Smart data placement — this from an HDD are evaluated at the automates the process of relocating extent or sub-volume level, which in data to the appropriate tier (either this case is a contiguous set of disk SDD or HDD). sectors that add up to 1 GB. Given that© 2010 Mesabi Group LLC Telephone: 781 326 003826 Country Lane Fax: 781 326 0038Westwood, Massachusetts 02090
  4. 4. Easy Tier Enables DS8700 Users to Make Good Use of Solid State DrivesCommentary Page 4this is really at the sub-volume level, The user takes into account all of thiseven with the smallest SSD (73 GB, information and gets a better feel forwhich means that 73 extents can be whether or not using SSDs makechosen), this level of granularity should sense, including how much data (frombe suitable for all practical purposes. a little to a lot) would benefit fromInitially, the frequency of access for all moving to SSDs. If the decision is madethe extents being evaluated is exam- to use SSDs, Easy Tier functionality inined over a period of, say, 24 hours. At the form of smart placement andthat point a continuum can be continuous workload monitoring cangenerated from the least frequently then take place.accessed extents on the “cold” side tothe most frequently accessed extents Smart Placementon the “hot” side. Of course, the Smart placement is the name for the“temperature” is relative (there is no process that Easy Tier goes through infreezing point!). moving selected extents from HDDs to SSDs (Figure 1). But it offers muchWorkload Hotspot Analysis more than doing this non-disruptivelyInformation collected from the heat as well as bi-directionally (SSD to HDDdistribution can be used to generate and vice versa) and dynamically overreports that can be used to determine SSDs might best be used. Note theanalysis does not presume that one or Figure 1: Tier Managed Extent Poolmore SSDs are already in place.This analysis looks across all physical SSD Arraysvolumes and their associated capacitythat are considered part of themonitoring process. Among the reportoutputs are the following:• The heat distribution for each Cold Extents Hot Extents volume, which is the capacity in Migrate Down Migrate Up each volume that would be targeted to SSDs (if not already there) or that has already been moved to an SSD.• The estimated migration time to move the data from HDDs to SSDs, if or when SSDs became available. HDD Arrays• The percentage of hot capacity as a Source: IBM and Mesabi Group April 2010 fraction of the total capacity.• The predicted performance im- Smart placement is about automating provement for a particular SSD a manual process as well. Traditional configuration over existing HDDs as disk storage mapping is about creating well as the expected improvement if rigid logical volumes. For example, a additional SSD capacity is added. high-performance-requiring application© 2010 Mesabi Group LLC Telephone: 781 326 003826 Country Lane Fax: 781 326 0038Westwood, Massachusetts 02090
  5. 5. Easy Tier Enables DS8700 Users to Make Good Use of Solid State DrivesCommentary Page 5is typically locked to Tier 1 drives that a good candidate for server virtual-may be underutilized (i.e., over- ization. Server virtualization, inprovisioned) in order to improve turn, means that the server can beperformance, as in the previously more effectively utilized by runningdiscussed short-stroking. more applications.Easy Tier uses the concept of hybridstorage volumes, where the physical Continuous Workload Monitoringvolumes in both Tier 0 and Tier 1 or The temperature of at least someTier 2 (SATA) logically appear homoge- extents change over time, so a one-timenous to an application, which means migration of the hottest data fromthat an application is unaware of any HDDs to SSDs would eventually lead tomovement of hot or cold data that suboptimal performance from the SSDexploits the appropriate storage tier. configuration, as the SSDs wouldLetting the storage system do it contain some “colder” data than wouldautomatically, reduces reconfiguration now be available on HDDs. Easy Tiertime and errors compared to a manual solves this problem through continu-configuration process. ous monitoring of the workloads on extents.Note that the Easy Tier algorithm ismulti-dimensional. For example, the Performance data is collected on everyalgorithm calculates the “cost and extent that has active I/O on everybenefit” of promoting an extent before monitored logical device in the actually does so. The algorithm The I/O statistics collected for eachcalculates whether the cost of promot- extent include read and write time,ing an extent is greater than the benefit amount of data transferred, andto performance of having that extent on cumulative response time. ThoseSSD. Thus, there is a check and statistics enable a more sophisticatedbalance on the movement of extents. analysis of performance ranking than just IOPS alone.Note that after the migration has takenplace, an IT organization may be able These statistics are collected at fixedto take one or both of the following periods of approximately 5 minutesactions that it couldn’t have taken and then are reported on at 15 minutebefore (and help economically justify intervals. The results are accumulatedthe use of SSDs if that is necessary): over a period of time, say, 24 hours. At the end of that time, the data access• Consolidate selected applications to pattern of all the extents will be fewer HDDs and use the freed up examined to create a new I/O heat map HDDs to meeting growing storage (i.e., iteratively go back to the workload requirements (which means delay- hotspot analysis phase) and from that ing the need to purchase additional map a new migration plan can be put HDD capacity). in place to promote or demote individ-• Decrease the I/O wait time on an ual extents (i.e., iteratively go back to existing physical server, which the smart placement step). means that either a smaller (and By the way, note that when Easy Tier is less costly) physical server might be on it will migrate data automatically, used or the existing server might be© 2010 Mesabi Group LLC Telephone: 781 326 003826 Country Lane Fax: 781 326 0038Westwood, Massachusetts 02090
  6. 6. Easy Tier Enables DS8700 Users to Make Good Use of Solid State DrivesCommentary Page 6but users have the option to use the neously in tandem, has been anmanual volume relocation compo- ongoing challenge.nent of Easy Tier to move a volume For DS8700 users, that challengeout of the Easy Tier managed extent has been resolved with the combina-pool at the volume level. tion of Easy Tier and Storage Tier Advisor. Now, users have the toolsConclusion and capabilities to manage thePerformance — by one definition, the balance between SSDs and HDDsefficiency with which something successfully, and to give thefulfills a purpose — is something performance that an applicationthat appears desirable in all cases. needs while not breaking the budgetBut is more “performance” always bank. So Easy Tier is something thatnecessary? The answer for many IT every DS8700 user should considerapplications, such as response time carefully when SSDs are a part of thein sending e-mails, is that existing picture.performance is good enough. Still,some growing IT applications(especially revenue-generating ones) David Hillwould clearly benefit from improvedperformance in most cases (if wedefine adequate performance assatisfactory response time for alarger number of transactions persecond). Moreover, adequateperformance does not mean cost-effective performance: Even applica-tions that deliver satisfactoryperformance may do so by way ofunnecessary hidden costs, such asadded disk space because of short-stroking, or excess server capacitydue to underutilization of serverscaused by excessive I/O wait times.Enter SSDs as Tier 0 in disk storagesystems. But understanding whereSSDs can best be used in conjunc-tion with HDDs, and managing thetwo tiers transparently and simulta-Analyst Name: David Hill Mesabi Group LLC is an affiliate of Valley View Ventures thatTopic Area: Storage Tiering aims to provide thought leadership and sound advice to both vendors and users of information technology. .Mesabi Group LLC26 Country Lane Phone: (781) 326-0038Westwood, MA 02090 email the author: davidhill@mesabigroup.comwww.mesabigroup.comThe information contained in this publication has been obtained from sources Mesabi Group LLC believes to be reliable, but is notwarranted by Mesabi Group LLC. Commentary opinions reflect the analyst’s judgment at the time and are subject to change withoutnotice. Unless otherwise noted, the entire contents of this publication are copyrighted by Mesabi Group LLC, and may not bereproduced, stored in a retrieval system, or transmitted in any form or by any means without prior written consent by Mesabi GroupLLC