HP StorageWorks MSA2000 Best Practices

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iSCSI, Fibre Channel, or SAS

When choosing the right HP StorageWorks MSA2000 model, you should determine your budget and performance needs. Each model has unique features that should be weighed when making your decisions.

Following are some distinct characteristics of each model.

Characteristics of the MSA2000i G1 model:

• iSCSI uses the Transport Control Protocol (TCP) for moving data over Ethernet media

• Offers SAN benefits in familiar Ethernet infrastructure

• Lower infrastructure cost

• Lower cost of ownership

Characteristics of the MSA2000fc G1 model:

• Offers a faster controller for greater performance

• The Fibre Channel controllers support 4 Gb for better throughput

• Integrates easily into existing fibre channel infrastructure

• More scalability, greater number of LUNs, and optional snapshots

Characteristics of the MSA2000sa G1 model:

• Supports ULP (Unified LUN Presentation)

• No need to set interconnect settings

• Lower cost infrastructure

Unified LUN Presentation (ULP)

The MSA2000sa G1use the concept of ULP. ULP can expose all LUNs through all host ports on both controllers. ULP appears to the host as an active-active storage system where the host can choose any available path to access a LUN regardless of vdisk ownership.

ULP uses the T10 Technical Committee of INCITS Asymmetric Logical Unit Access (ALUA) extensions, in

SPC-3, to negotiate paths with aware host systems. Unaware host systems see all paths as being equal.

Overview:

ULP presents all LUNS to all host ports

• Removes the need for controller interconnect path

• Presents the same WWNN for both controllers

Shared LUN number between controllers with a maximum of 512 LUNs

• No duplicate LUNs allowed between controllers

• Either controller can use any unused logical unit number

ULP recognizes which paths are “preferred”

• The preferred path indicates which is the owning controller per ALUA specifications

• “Report Target Port Groups” identifies preferred path

• Performance is slightly better on preferred path

Write I/O Processing with ULP

• Write command to controller A for LUN 1 owned by Controller B

• The data is written to Controller A cache and broadcast to Controller A mirror

• Controller A acknowledges I/O completion back to host

• Data written back to LUN 1 by Controller B from Controller A mirror

Figure 1: Write I/O Processing with ULP

LUN 1

B Owned

Read I/O Processing with ULP

• Read command to controller A for LUN 1 owned by Controller B:

– Controller A asks Controller B if data is in Controller B cache

– If found, Controller B tells Controller A where in Controller B read mirror cache it resides

– Controller A sends data to host from Controller B read mirror, I/O complete

– If not found, request is sent from Controller B to disk to retrieve data

– Disk data is placed in Controller B cache and broadcast to Controller B mirror

– Read data sent to host by Controller A from Controller B mirror, I/O complete

Figure 2: Read I/O Processing with ULP

LUN 1

B Owned

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