energy efficient storage technologies for data centers alan g. yoder, ph.d. netapp chair, snia...

Energy Efficient Storage Technologies for Data Centers

Alan G. Yoder, Ph.D.NetApp

Chair, SNIA Technical Council

Energy Efficient Storage Technologies for Data Centers© 2010 Alan G. Yoder. All Rights Reserved.

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Abstract

Energy Efficient Storage Technologies for Data CentersAn impressive amount of work has been done to date on improving the electrical efficiency of various data center components. The data storage industry has begun to see the fruits of this effort, with increased power supply and fan efficiencies. However, storage presents other significant opportunities for energy conservation, through various types of capacity optimization, that are not captured in electrical efficiency discussions. As data storage uses on the order of 25% of IT power in an average data center, these other opportunities bear examination. This article presents a survey of emerging storage technologies which positively impact energy usage and presents current thinking in the storage industry regarding their relative effectiveness. It also attempts to set a baseline for configurations against which improvements in capacity and energy use can be made.


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Outline

Purpose of paperWhat is “storage”?What is “storage efficiency”?Baseline data center storage configurationStorage optimizing technologiesBallpark savings guesstimatesSNIA activitiesConclusion


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Purpose of paper

Introduce storage as a separate and special problem in energy efficiency

Data at rest requirements

Set baseline for comparison of purported improvementsEstablish a taxonomy for ways of saving energySurvey of what industry has been doing in the area of energy efficiency


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What is “storage”?

At homeApple Time Machine + 2 USB drives (one offsite)

In the labLinux/BSD box and a few SATA drives

In the data centerHi performance (both latency and bandwidth)Petabyte scaleRAS (reliability, availability, serviceability)

5 9’s availability or better (< 5 min unplanned downtime / yr)RPO of minutes or less (sometimes zero)RTO of minutesnon-disruptive firmware and hardware upgrades

Something always broken, yet life goes on


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What is “storage efficiency”?

Electrical efficiencyHow much heat is generated during the conversion of electrical energy into useful work?Good for CPUs, maybe for data in flight

Storage efficiencyHow much data can be crammed into a box using a given amount of electricity and raw capacity(Definitions are still a work in progress)

All based around sizeof(data) and sizeof(raw capacity)


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Baseline configuration

No single point of failure (no SPOF)*everything* is redundantRAID 1dual pathingpower supplies operate at 50% load (or less)

No system-wide reboots*everything* is hot-swappable

High performance (SAN emulates Direct Attach)

Fibre Channel drives


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Summary of baseline configuration

No SPOFRAID 1FC drives

This configuration has ruled Tier 1 storage in the data center for 15 yearsEmphasis on performance and data safety


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Storage optimizing technologies

Electrical efficiencyDisk spindownPower supply and fan efficiency, andSSDs

Capacity optimizationDelta snapshotsThin provisioningAdvanced RAIDData deduplicationCompression

Hybrid systemsSlow SATA drives + flash


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A nod to facilities optimization

Usually the most energy savings are gotten here

PUE = ratio of input power to IT power

Traditional PUE: 2.25 and upModern PUE: 1.2

Air economizers, variable speed fans, flywheel UPSs, etc.Savings of over 50% often possible

Impossible to obtain with IT equipment optimizations assuming old-style power delivery inefficiencies (PUE > 2.0)


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Storage Efficiency: 4 techniques

Make the equipment more energy efficientUse less redundancyCommit less spaceSqueeze more data into available space


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Making equipment more energy efficient

Power supply efficiency80plus, Climate Savers, US EPAEfficiencies driven from ~65% to ~90% and up

Variable speed fansPower theoretically quadratic in rotational speedGreat opportunityNot enough operational data to date

Disk spindownLooks great on paper; problematic in practice

RAID groups, background housekeepingOnly suitable for secondary storage due to latency hit

So far not viable in marketplace


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Better energy efficiency (cont.)

SSDsSeemingly ideal

Zero data at rest energy (caveat: housekeeping requirements an open question)Data in flight energy scales with IOPs

Price barriers to widespread adoption

High-capacity drives with flashPerformance about as good as FC

No free lunch caveat: except when at write saturation

1/6 the energy density of FC at restQuestion: will the flash migrate to the host?


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Using less redundancy

RAID 150% space efficiency

Storage bricks (Google et al)typically 33% or less

similar to RAID 1 + online backupmuch worse if CPUs aren’t occupied with useful work

RAID 5Recommended raid group size of 5 to 880% to 88% efficiency

RAID 6Recommended raid group size of 10 to 1680% to 88% efficiencyMoving to this because of convergence of BER and disk size on modern systems ~4% chance annually of 2nd disk failure during RAID reconstruct on a 100-disk array


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Using less redundancy (cont.)

• Delta snapshots– shared-data PIT copies– technology is similar to vfork– read-only and read-write variants– many data protection and what-if scenarios

satisfied with deltas instead of full copies


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Committing less space

• Thin provisioning– Works similarly to user quotas in filesystems– Impressive gains, because

• Volumes are overprovisioned (more space for files than used)

• Systems are overprovisioned (more space for volumes than used)


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Squeezing more data into available space

• Compression– Harder on block storage (quantization)

• Deduplication– Savings are most impressive on secondary

storage– Global dedup an unsolved problem

• Communication, index overhead• You *better* not lose that base copy!


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Average savings (from baseline or historical figures)

Technology SavingsFacilities optimization 50% Power supply improvements 20%Variable speed fans unknownLarge capacity drives 80%Advanced RAID 40%Delta snapshots 90% +Thin provisioning 50%In-place data deduplication 27% (Netapp: 1 exaByte)

Compression 20% +


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Storage procural politics

• IT guys don’t pay utility bill (OPEX)– So they don’t care how power efficient the

storage is until they hit a density wall

• Capacity optimizing technologies affect CAPEX as well as OPEX

– Capacity optimizing technologies allow them to buy less gear to store the same data

– IT guys do care about this


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SNIA activities

• GSI – Green Storage Initiative– Collect and harmonize industry feedback for US EPA– Evangelize technical work– Develop labeling program

• Green TWG – Technical Working Group– IP-protected group– Idle and active power metrics

• Capacity Optimization subgroup (of TWG)– Characterization of capacity optimization technologies

• Tutorials, whitepapers, etc.– At SNW trade shows, in FarSighted magazine


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Baseline configuration revisited

• For research into data center class storage– Disk subsystems

• No SPOF in shelves• Multipathing• RAID 6 (or 5 if 6 is unavailable)• 100 or more disks

– Controllers• No SPOF• Multipathing• Multiprotocol (NFS + CIFS)• Thin provisioning, delta snapshots, compression,

dedup all operational


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Questions

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