2015 deploying flash in the data center

Deploying Flash in the Data Center
Or How this
Flash
Makes Storage Like This Flash®

Today’s Agenda
 The storage performance problem
 Flash to the rescue
• A brief flash memory primer
• Flash/SSD types and form factors
 The All Flash Arrays (AFA)
 Hybrid arrays
 Server side flash
 Converged architectures
 Choosing a solution

The IO Gap
 Processor speed doubles every 2-3 years
 Disks have been stuck at 15K RPM since 2000

“The I/O Blender” Strains Storage
 Virtualization throws I/O into a
blender… all I/O is now random I/O!
 10 VMs doing sequential I/O to the
same datastore=random I/O
 Disk drives are good at sequential,
less good at random

The Noisy Neighbor Moves In
 Dedicated spindles are like solid walls
• Applications have limited effect on each other
– Backups excepted – Same data
 Shared datastores provide no protection
• 1 application demanding 10,000 IOPS will slow
the others.
App1 App2 App1 App2 AppN App4
Then Now

VDI Presents Unique Workloads
 Highly variable but coincident (boot/login in AM)
 Steady state 50+% write
 40+% of projects fail due to storage performance

Data Access Performance
 L1 processor cache ~1ns
 L2 processor cache ~4ns
 Main memory ~100ns
 PCIe SSD read 16-60μs (16,000-60,00ns)
 SAS/SATA SSD read 50-200μs (50,000-
200,000ns)
 Disk read 4-50ms (4-50,000,000ns)
Moral of the story: keep IOPS away from the disk

Traditional Performance Solutions
 Head per track disk drives, DRAM SSDs
• Huge price premium limits use to the very few
 Wide Striping
• A 15K RPM disk delivers 200 IOPS
• For 10,000 IOPS spread load across 50 drives
– Of course that’s 15PB of capacity
• Short stroking
– Use just outside tracks to cut latency
 Wasting capacity wastes $ and OpEx (power, maint)

What Is Flash Memory?
 Solid State, Non-volatile memory
• Stored charge device
• Not as fast as DRAM but retains
 Read/Write blocks but must erase 256KB-
1MB pages
• Erase takes 2ms or more
• Erase wears out cells
 Writes always slower than reads

The Three, & ½, Types of Flash
 Single Level Cell (SLC) (1bit/cell)
• Fastest
• 50,000 program/erase cycle lifetime
 Multi Level Cell (MLC) (2 bits/cell)
• Slower
• 3,000 program/erase cycle lifetime
 eMLC or HET MLC (2 bits/cell)
• Slightly slower writes
• 12-20,000 cycles
 Triple Level Cell (TLC) (3 bits/cell)
• 3D/LDPC boosts endurance to data
center level

Flash’s Future
 Smaller cells are denser, cheaper,
crappier
• Today’s 1x nm cells (15-19nm) last planar node
 3D is the future
• Samsung now shipping 3D
• Others sampling
– SanDisk/Toshba 256GB/chip
 Other technologies post 2020
• PCM, Memristors, Spin Torque,

Anatomy of an SSD
 Flash Controller
• Provides external interface
– SAS, SATA, PCIe
• Wear leveling
• Error correction
– Shifting to LDPC
 DRAM
• Write buffer & Metadata
 Ultra or other capacitor
• Power failure DRAM dump
• Enterprise SSDs only

Flash/SSD Form Factors
 SATA 2.5”
• The standard for laptops, good for servers
 SAS 2.5”
• Dual ports for dual controller arrays
 PCIe
• Lower latency, higher bandwidth
• Blades require special form factors
• M.2 for small form factors like notebooks
• U.2 for 2.5” hot swap

U.2/SFF-8639 PCIe for 2.5” SSDs
 Adds x4 PCIe 3.0 lanes to SAS/SATA
connector
• Dual ports to x2
 Appearing on new servers
• Making PCIe/NVMe SSDs hot swappable
 Next step for storage arrays
14

Enter NVMe
 New logical interface for PCIe storage
• Replaces ACHI
 More, deeper queues
 Simpler command set
 Lower latency
• 300 vs 500+µs
15

SSDs use Flash but Flash≠SSD
 Fusion-IO cards
• Atomic Writes
– Send multiple writes (eg: parts of a database transaction)
• Key-Value Store
• FTL runs in host CPU

Diablo Puts Flash on the Memory Bus
 Memory Channel Flash
(SanDisk UltraDIMM)
• Block storage or direct memory
• Write latency as low as 3µsec
• Requires BIOS support
 Memory1
• 400GB/DIMM
• No BIOS/OS Support
• Volatile 17

Selecting SSDs
 Trust your OEM’s qualification
• They really do test
 Most applications won’t need 100K IOPS
 Endurance ≠ reliability
• SSDs more reliable than HDDs
– 2 million hr MTBF
– 10^17 BER vs 10^15 for near line HDD
• Wear out is predictable
• Consider treating SSDs as consumables
• However don’t use read optimized drive in write heavy
environment

SanDisk’s Enterprise SATA SSDs
Name Sizes IOPS r/w Endurance Application
Eco 240, 480, 960 80K/15K 1 DWPD, 3yr Read intensive
Ascend 240, 480, 960 75K/14K 1 DWPD, 3yr Read intensive
Ultra 200, 400, 800 75K/25K 3 DWPD, 5yr General purpose
Extreme 100, 200, 400, 800 75K/25K 10 DWPD, 5yr Write intensive
DWPD = Drive Writes Per Day

Consistent Performance is Key
20

Flash for Acceleration
 There are 31 flavors of flash usage
 What’s best for you depends on your:
• Application mix
• IOPS demand
• Tolerance of variable performance
• Pocketbook
• Organizational politics

Basic Deployment Models
 SSDs in server as disk
 All solid state array
 Hybrid arrays
• Sub LUN tiering
• Caching
 Storage Network Caching
 Server side caching
 Hyperconverged infrastructures

Flash in the Server
 Minimizes latency and maximizes bandwidth
• No SAN latency/congestion
• Dedicated controller
 But servers are unreliable
• Data on server SSD is captive
• Good where applications are resilient
– Web 2.0
– SQL Server Always On
 Software cross-server mirroring
• But that adds latency to writes

All Flash Array Vendors Want You to
Think of This

Rackmount SSDs
 Our drag racers
• They go fast but that’s all they do
 The first generation of solid state
 Not arrays because:
• Single Controller
• Limited to no data services
• Thankfully dying out

The Hot Rods
 Legacy architectures with SSD replacing
HDD
• NetApp EF550
• EMC VNX-F
• Equallogic PS6110s
• Many 2nd and 3rd tier vendor’s AFAs
 Limited performance
– 50-300,000 IOPS
 Full set of data management features
 Wrong architecture/data layout for flash

All Solid State Arrays
 Minimum dual controllers w/failover
 Even better scale-out
 Higher performance (1 megaIOP or better)
 Better scalability (100s of TB)
 Most have partial data management features
• Snapshots, replication, thin provisioning, REST, Etc.
 May include data deduplication, compression
• Lower cost w/minimal impact on performance

Legacy Vendors All Flash Array
 3Par and Compellent’s data layout better for flash
• Easier tiering, less write amplification
 Dell - Compellent
• Mixed flash
– SLC write cache/buffer, MLC main storage
• Traditional dual controller
 HP 3Par Storeserv 7450
• 220TB (Raw)
• 2-4 controllers

Pure Storage Flasharray//m
 Dual x86 Controllers in canisters 3u
 300 KIOPS
 SAS shelves, U.2 ports in head
 PCIe NVRAM shared
 2.75-35TB raw capacity
 Always on compress and dedupe
 FC, iSCSI or FCoE

SolidFire
 Scale out architecture
• 5 node starter 174TB (raw) 375K IOPS
• Scale to 100 nodes
 Always on dedupe, compression
 Content addressed SSDs
 Leading storage QoS
 Moving from cloud providers to
enterprise
 iSCSI, FC via bridge nodes

EMC XtremIO
 Scale-out Fibre Channel
 X-Brick is 2 x86 servers w/SSDs
 Scales to 8 X-Bricks (but not online)
 Infiniband RDMA interconnect
 Shared memory requires UPS
 Full time dedupe, CAS
 10-80TB raw

Violin Adds Services
 Violin was market leader in hotrod era
 That’s not enough
 Windows Flash Array - WSS on 6000 array
 Concerto 7000 storage routers ala Whiptail
• Snapshots, replication Etc. via Falconstor
• Scale to 280TB
 Unique flash modules
• PCIe switched
• Better consistency10/6/2015

Hybrid Arrays
 Combine flash and spinning disk in one system
• Usually 7200RPM
 Legacy designs with SSDs added
 Next-Gen Hybrids
– Tegile - Nimble
– NexGen - Tintri
 High performance
• 20,000 IOPS or more from 3-4u
• 10% flash usually provides 2-4x performance boost
 Typically include deduplication, compression,
virtualization features

Sub-LUN Tiering
 Moves “hot” data from slow to fast
storage
 Only 1 copy of data
 Must collect access frequency
metadata
 Usually on legacy arrays
 Ask about granularity, frequency
• Up to 1GB, once a day
 Can give unpredictable performance

Flash Caching
 Data copied to flash on read and/or write
 Real time
 Write around
• Reads cached
 Write-through cache
• All writes to disk and flash synchronously
• Acknowledgment from disk
 Write back cache
• Write to flash, spool to disk asynchronously

Server Flash Caching Advantages
 Take advantage of lower latency
• Especially w/PCIe flash card/SSD
 Data written to back end array
• So not captive in failure scenario
 Works with any array
• Or DAS for that matter
 Allows focused use of flash
• Put your dollars just where needed
• Match SSD performance to application
• Politics: Server team not storage team solution

Caching Boosts Performance!
0
500
1000
1500
2000
2500
3000
3500
Baseline PCIe SSD
Cache
Low end SSD
Cache
Published TPC-C results

Write Through and Write Back
0
10000
20000
30000
40000
50000
60000
Baseline Write Through Write Back
TPC-C IOPS
• 100 GB cache
• Dataset 330GB grows to 450GB over 3 hour test

Server Side Caching Software
 Over 20 products introduced
 Some best for physical servers
• Windows or Linux
 Others for hypervisors
• Live migration/vMotion a problem
 Most provide write through cache
• No unique data in server, only accelerates reads
 Duplicated, distributed cache for write back
 Applications cache too
• SQL Server

Live Migration Issues
 Does cache allow migration
• Through standard workflow
– To allow automation like DRS?
 Is cache cold after migration?
 Cache coherency issues
 Guest cache
• Cache LUN locks VM to server
– Can automate but breaks workflow
 Hypervisor cache
• Must prepare, warm cache at destination

Distributed Cache
 Duplicate cached writes across n servers
 Eliminates imprisoned data
 Allows cache for servers w/o SSD
 Solutions
• PernixData
• Dell Fluid Cache

Datrium DiESL
 Host managed cache
 PCIe SSD in Host
• Write through cache
 All flash NetShelf
• Persistent layer
 NFS interface to vSphere
• Per-VM data services
 Founders from Data Domain
• Dedupe of course
45

Virtual Storage Appliances
 Storage array software in a VM
 iSCSI or NFS back to host(s)
 Caching in software or RAID
controller
 Players:  VMware
 StoreMagic
 HP/Lefthand
 Nexenta

Hyperconvirged Infrastructure
(ServerSAN)
 Use server CPU and drive slots for storage
 Software pools SSD & HDD across multiple
servers
 Data protection via n-way
replication
 Can be sold as hardware
or software
• Software defined/driven

ServerSAN Products
 VMware’s VSAN
• Scales from 4-32 nodes
• 1 SSD, 1 HDD required per node
 Maxta Storage Platform
• Data optimization (compress, dedupe)
• Metadata based snapshots
 EMC ScaleIO
• Scales to 100s of nodes
• Hypervisor agnostic
 Atlantis Computing ILIO USX
• Uses RAM and/or Flash for acceleration
• Works with shared or local storage

ServerSAN Architecture Differentiators
 Data protection model
• Per node RAID?
• N-way replication
• Network RAID?
 Flash usage:
• Write through or write back cache
• SubLUN tiering
 Prioritization/storage QoS
 Data locality
 Data reduction
 Snapshots and cloning

Hyper-converged Systems
 Nutanix
• Derived from Google File System
• 4 nodes/block
• Multi-hypervisor
• Storage for cluster only
 Simplivity
• Dedupe and backup to the cloud
• Storage available to other servers
• 2u Servers
 No 20 other vendors incl. VMware’s EVO:RAIL

Questionable Idea 1:
Smart Shelves
 How rack mount SSDs become arrays
 Adds data services/scale out in storage router
 Players:
• Cisco Whiptail
• Violin
• XIO Storage
Appliance
Storage Router Storage Router
Storage
Appliance
HP
ProLiant
DL380 G6
FANS
PROC
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ProLiant
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ProLiant
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Storage
Appliance
Storage
Appliance
Workloads

Questionable Idea #2:
Storage Network Caching
 “bump in the wire” cache
 Several vendors offered
Fibre Channel versions
• All discontinued
 NAS versions
• Flopped in general market
• Work as cloud gateways
– Avere
• HPC
– DDN
5210/6/2015
Workloads
Storage
Caching
Appliance(s)

All Flash Array?
 If you need:
• More than 75,000 IOPS
• For one or more high ROI applications
 Expect to pay $4-7 GB
 Even with dedupe
 Think about data services
• Snapshots, replication, Etc.

Hybrids
 Hybrids fit most users
• High performance to flash, capacity from disk
• All automatic
 Look for flash-first architectures
• Usually but not always from newer vendors
 Ask about granularity and frequency for tiering
 Again data services
• Snaps on HDD
• Per-VM services

I’ll give up Fibre Channel,
When you pry it from my cold dead
hands

Server Side Caching
 Decouples performance from capacity
 Strategic use
• Pernix data write back cache w/low cost array
 Tactical solution
• Offload existing array
• Boost performance with minimal Opex

Questions and Contact
 Contact info:
• Hmarks@deepstorage.net
• @DeepStoragenet on Twitter

2015 deploying flash in the data center

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Editor's Notes