Rearchitecting Storage for Server VirtualizationStephen FoskettOct 21, 2010

This is Not a Rah-Rah Session

Agenda•First 45 minutes

▫Impact of hypervisors on I/O▫VM storage approaches▫VM connectivity options

•Break•Second 45 minutes

▫Storage features for VM▫Questions and comments

Introducing Virtualization

Poll: Who Is Using VMware?

VMware

None

MicrosoftOther

Virtualization Users

Source: A dozen analyst SWAGs

Server Virtualization “The I/O Blender”

•Shared storage is challenging to implement

•Storage arrays “guess” what’s coming next based on allocation (LUN) taking advantage of sequential performance

•Server virtualization throws I/O into a blender – All I/O is now random I/O!

Server Virtualization requires SAN and NAS•Server virtualization has transformed the

data center and storage requirements▫VMware is the #1 driver of SAN adoption

today!▫60% of virtual server storage is on SAN or

NAS▫86% have implemented some server

virtualization•Server virtualization has enabled and

demanded centralization and sharing of storage on arrays like never before!

Server Virtualization Recoil•Dramatically increased I/O•“Detrimental” to storage utilization•Patchwork of support, few standards

▫“VMware mode” on storage arrays▫Virtual HBA/N_Port ID Virtualization (NPIV)▫Everyone is qualifying everyone and

jockeying for position•Befuddled traditional backup, replication,

reporting

Three Pillars of VM Performance

Poll: Does Server Virtualization Improve Storage Utilization?

Hypervisor Storage Approaches

Hypervisor Storage Options:Shared Storage

• Shared storage - the common/ workstation approach▫ Stores VMDK image in VMFS datastores

▫ DAS or FC/iSCSI SAN

▫ Hyper-V VHD is similar

• Why?▫ Traditional, familiar, common (~90%)

▫ Prime features (Storage VMotion, etc)

▫ Multipathing, load balancing, failover*

• But…▫ Overhead of two storage stacks (5-8%)

▫ Harder to leverage storage features

▫ Often shares storage LUN and queue

▫ Difficult storage management

VMHost

GuestOS

DAS or SANStorage

VMFS VMDK

Hypervisor Storage Options:Shared Storage on NFS

• Shared storage on NFS – skip VMFS and use NAS▫ NTFS is the datastore

• Wow!▫ Simple – no SAN

▫ Multiple queues

▫ Flexible (on-the-fly changes)

▫ Simple snap and replicate*

▫ Enables full Vmotion

▫ Use fixed LACP for trunking

• But…▫ Less familiar (3.0+)

▫ CPU load questions

▫ Default limited to 8 NFS datastores

▫ Will multi-VMDK snaps be consistent?

VMHost

GuestOS

NFSStorage

VMDK

Hypervisor Storage Options:Raw Device Mapping (RDM)• Raw device mapping (RDM) -

guest VM’s access storage directly over iSCSI or FC▫ VM’s can even boot from raw devices

▫ Hyper-V pass-through LUN is similar

• Great!▫ Per-server queues for performance

▫ Easier measurement

▫ The only method for clustering

• But…▫ Tricky VMotion and DRS

▫ No storage VMotion

▫ More management overhead

▫ Limited to 256 LUNs per data center

VMHost

GuestOS

SAN Storage

Mapping File

I/O

Physical vs. Virtual RDMVirtual Compatibility

Mode• Appears the same as a

VMDK on VMFS• Retains file locking for

clustering• Allows VM snapshots,

clones, VMotion• Retains same

characteristics if storage is moved

Physical Compatibility Mode

• Appears as a LUN on a “hard” host

• Allows V-to-P clustering,a VMware locking

• No VM snapshots, VCB, VMotion

• All characteristics and SCSI commands (except “Report LUN”) are passed through – required for some SAN management software

Physical vs. Virtual RDM

Which VMware Storage Method Performs Best?

Mixed Random I/O CPU Cost Per I/O

Source: “Performance Characterization of VMFS and RDM Using a SAN”, VMware Inc., 2008

VMFS,RDM (p), or RDM (v)

Storage Connectivity Options

Which Storage Protocol To Use?•Server admins don’t know/care about

storage protocols and will want whatever they are familiar with

•Storage admins have preconceived notions about the merits of various options:▫FC is fast, low-latency, low-CPU, expensive▫NFS is slow, high-latency, high-CPU, cheap▫iSCSI is medium, medium, medium, medium

vSphere Protocol Performance

vSphere CPU Utilization

vSphere Latency

Microsoft Hyper-V Performance

The Upshot: It Doesn’t Matter• Use what you have and are familiar with!• FC, iSCSI, NFS all work well

▫Most enterprise production VM data is on FC, many smaller shops using iSCSI or NFS

▫Either/or? - 50% use a combination• For IP storage

▫Network hardware and config matters more than protocol (NFS, iSCSI, FC)

▫Use a separate network or VLAN▫Use a fast switch and consider jumbo frames

• For FC storage▫8 Gb FC/FCoE is awesome for VM’s▫Look into NPIV▫Look for VAAI

Break Time!

Stephen Foskettstephen@fosketts.nettwitter.com/sfoskett+1(508)451-9532

FoskettServices.comblog.fosketts.net

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VMware Storage Features

What’s New in vSphere 4•VMware vSphere 4 (AKA ESX/ESXi 4) is a

major upgrade for storage▫Lots of new features like thin provisioning,

PSA, Any-to-any Storage VMotion, PVSCSI▫Massive performance upgrade (400k IOPS!)

•vSphere 4.1 is equally huge for storage▫Boot from SAN▫vStorage APIs for Array Integration (VAAI)▫Storage I/O Control (SIOC) aka DRS for

Storage

Storage Features By License

Native VMware Thin Provisioning

• VMware ESX 4 allocates storage in 1 MB chunks as capacity is used▫Similar support enabled for virtual disks on NFS in

VI 3▫Thin provisioning existed for block, could be

enabled on the command line in VI 3▫Present in VMware desktop products

• vSphere 4 fully supports and integrates thin provisioning▫Every version/license includes thin provisioning▫Allows thick-to-thin conversion during Storage

Vmotion• In-array thin provisioning also supported (we’ll

get to that…)

Pluggable Storage Architecture• VMware ESX includes multipathing

built in▫ Basic native multipathing (NMP) is

round-robin fail-over only – it will not load balance I/O across multiple paths or make more intelligent decisions about which paths to use

▫ E+ Only: vSphere 4 Pluggable Storage Architecture allows third-party developers to replace ESX’s storage I/O stack

• There are two classes of third-party plug-ins:▫ Path-selection plugins (PSPs)

optimize the choice of which path to use, ideal for active/passive type arrays

▫ Storage array type plugins (SATPs) allow load balancing across multiple paths in addition to path selection for active/active arrays

• EMC PowerPath/VE for vSphere does everything

vStorage APIs for Array Integration (VAAI)• vSphere 4.1 only!• Array-based “Full Copy”

command offloads operations to array snapshots for Storage VMotion

• Acceleration of storage I/O - think "I/O" dedupe (not to be confused with data deduplication

• Hardware-assisted locking on a block-by-block basis (rather than entire LUN)

• Array-based thin provisioning integration using TRIM, zeroing, etc

• Supposed to have thin provisioning stun, but it’s AWOL

Storage I/O Control (SIOC)• “SIOC provides a dynamic control

mechanism for proportional allocation of shared storage resources to VMs running on multiple hosts”

• ESX can provide quality of service for storage access to virtual machines▫ Enabled on the datastore object, when

a pre-defined latency level is exceeded on a VM it begins to throttle I/O based on the shares assigned to each VM

▫ SIOC is aware of the storage array device level queue slots as well as the latency of workloads and decides how it can best keep machines below the predefined latency tolerance by manipulating all the ESX host I/O queues

▫ Introduce an element of I/O fairness across a datastore

• But:▫ vSphere 4.1 and Enterprise Plus only▫ Only supported with block storage (FC

or ISCSI)▫ Does not support RDM’s or datastores

constructed of extents, only 1:1 LUN to datastore mapping

Why NPIV Matters• N_Port ID Virtualization (NPIV)

gives each server a unique WWN▫ Easier to move and clone*

virtual servers ▫ Better handling of fabric login▫ Virtual servers can have their

own LUNs, QoS, and zoning▫ Just like a real server!

• When looking at NPIV, consider:▫ How many virtual WWNs does

it support? T11 spec says “up to 256”

▫ OS, virtualization software, HBA, FC switch, and array support and licensing

▫ Can’t upgrade some old hardware for NPIV, especially HBAs

Virtual Server

Virtual Server

Virtual Server

21:00:00:e0:8b:05:05:04

Without NPIV

Virtual Server

Virtual Server

Virtual Server

…05:05:05

With NPIV

…05:05:06 …05:05:07

Intel VMDq, VMDc, MS RSS• VMDq is like NPIV for

network cards▫ Hardware-assisted sorting

of virtual network cards▫ Uses MAC address▫ Requires special driver

• Supported on ESX and Hyper-V

• Two more technologies:▫ VMDc is different – Intel’s

networking take on SR-IOV

▫ Microsoft RSS allocates work to multiple CPU cores

And Then There’s VDI…•Desktop Virtualization (VDI) takes

everything we just worried about and amplifies it▫Massive I/O crunches▫Huge duplication of data▫More wasted capacity▫More user visibility▫More backup trouble

Thank You!

Stephen Foskettstephen@fosketts.nettwitter.com/sfoskett+1(508)451-9532

FoskettServices.comblog.fosketts.net

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