HP StorageWorks 2000i HP StorageWorks 2000 G2 Modular Smart Array reference gu - Page 40
Changing cache settings, Changing the synchronize-cache mode, Changing the missing LUN response
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Changing cache settings Changing the synchronize-cache mode You can control how the storage system handles the SCSI SYNCHRONIZE CACHE command. Typically you can use the default setting. However, if the system has performance problems or problems writing to databases or other applications, contact technical support to determine if you should change this option. To change the synchronize-cache mode 1. In the Configuration View panel, right-click the system and select Configuration > Advanced Settings > Cache. 2. Set Sync Cache Mode to either: • Immediate. Good status is returned immediately and cache content is unchanged. This is the default. • Flush to Disk. Good status is returned only after all write-back data for the specified volume is flushed to disk. 3. Click Apply. Changing the missing LUN response Some operating systems do not look beyond LUN 0 if they do not find a LUN 0 or cannot handle noncontiguous LUNs. The Missing LUN Response option handles these situations by enabling the host drivers to continue probing for LUNs until they reach the LUN to which they have access. This option controls the SCSI sense data returned for volumes that are not accessible because they don't exist or have been hidden through volume mapping (this does not apply to volumes of offline vdisks). Use the default value unless a service technician asks you to change it to work around a host driver problem. To change the missing LUN response 1. In the Configuration View panel, right-click the system and select Configuration > Advanced Settings > Cache. 2. Set Missing LUN Response to either: • Not Ready. Sends a reply that there is a LUN where a gap has been created but that it's "not ready." Sense data returned is a Sense Key of 2h and an ASC/ASCQ of 04/03. This option is the default. • Illegal Request. Sends a reply that there is a LUN but that the request is "illegal." Sense data returned is a Sense Key of 5h and an ASC/ASCQ of 25/00. 3. Click Apply. Controlling host access to the system's write-back cache setting You can prevent hosts from using SCSI MODE SELECT commands to change the system's write-back cache setting. Some operating systems disable write cache. If host control of write-back cache is disabled, the host cannot modify the cache setting. The default is Disabled. This option is useful in some environments where the host disables the system's write-back cache, resulting in degraded performance. To change host access to the write-back cache setting 1. In the Configuration View panel, right-click the system and select Configuration > Advanced Settings > Cache. 2. Either select (enable) or clear (disable) the Host Control of Write-Back Cache option. 3. Click Apply. 40 Configuring the system