Volume Read Ahead Settings; Multi Path I/O (Mpio) - HP ProLiant DL980 G7 Technical White Paper

Hp 85 tb reference architectures for microsoft sql server 2012 fast track data warehouse: hp proliant dl980 g7 and p2000 g3 msa storage

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Technical white paper | HP ProLiant DL980 G7 and P2000 G3 MSA Storage

Volume Read Ahead settings

The P2000 G3 arrays contain provisions that allow for the setting of custom Read Ahead cache settings for each volume.

Several variations of read ahead settings were tested with Fast Track configurations, and we have found that the setting of

1MB provides the best performance. The Read Ahead setting must be set on EACH volume in the configuration. Figure 4

below details the process for setting read ahead on a P2000 G3 volume.

Figure 4. P2000 G3 Volume Read Ahead Setting

Simply highlight a volume, then select "Configuration"  "Modify Volume Cache Settings" and then modify the box labeled

"Read Ahead Size". Repeat for each volume in the configuration.

The solution presented here presents a total of 88 paths per LUN (22 HBA ports X 4 storage ports). This number of paths is

greater than the 32 paths supported by Microsoft Windows® Server 2008 R2 MPIO. For this reason, manual path

configuration must be employed. Using the management interface on the P2000 arrays, explicit mappings must be created,

matching up a single storage port with a single HBA port on the server. Two paths per HBA can be set up, with the MPIO

policy "Failover Only". This will direct MPIO to use a single path only and failover to the second or secondary path when the

first one fails. For more detailed information, refer to the HP published document: "Microsoft SQL Server Fast Track: HP

P2000 G3 MSA Multipath I/O configuration and best practices",

http://h20195.www2.hp.com/V2/getdocument.aspx?docname=4AA0-9466ENW.

Since this configuration uses 2 Data LUNs per array rather than the typical 4, we must adjust the manual MPIO mapping

scheme. In order to take advantage of the load balancing capability in the P2000 arrays, each LUN must be mapped across 2

storage ports residing on the SAME storage controller. Each LUN can have mappings to more than 1 HBA or HBA port, but it

cannot be mapped across storage controllers (port A1, and port B2 for example). Table 8 below shows an example of the

correct mappings for DL980 G7 LUNs residing on a P2000 array:

Table 8. Manual Mappings for DL980 G7 LUNs

LUN

Array1, LUN1

Array1, LUN2

Storage Port

HBA Port

HBAport 2A

HBAport 3B

HBAport 3A

HBAport 4A

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P2000 g3