HP P2000 G3 MSA Technical White Paper

Technical white paper | HP P2000 G3 MSA
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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
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

HP P2000 G3 MSA Specifications

General

Model	HP P2000 G3 MSA
Form Factor	2U
Drive Types	SAS, SATA
Controllers	Dual controllers
Host Interface	SAS, iSCSI, Fibre Channel
RAID Levels	0, 1, 5, 6, 10
Management	Web-based, CLI
Cache Memory	2 GB per controller