Dell H700, H800 manual CacheCade, Cut-Through IO, Reconfiguring Virtual Disks

Dell

Feature	PERC H700	PERC H700 Modular	PERC H800 Adapter
	Integrated/Adapter
Clustering	Card and software		Not supported
	stack enables High
	Availability Clusters

4.2CacheCade

CacheCade provides cost-effective performance scaling for database-type application profiles in a host-based RAID environment by extending the PERC RAID controller cache with the addition of Dell- qualified Enterprise SSDs.

CacheCade identifies frequently-accessed areas within a data set and copies this data to a Dell- qualified, Enterprise SSD (SATA or SAS), enabling faster response time by directing popular Random Read queries to the CacheCade SSD instead of to the underlying HDD.

Supporting up to 512 GB of extended cache, CacheCade SSDs must all be the same interface (SATA or SAS) and will be contained in the server or storage enclosure where the RAID array resides. CacheCade SSDs will not be a part of the RAID array.

CacheCade is a standard feature on, and only available with, the PERC H700/H800 1 GB NV Cache RAID controller.

CacheCade SSDs can be configured using the PERC BIOS Configuration Utility or OpenManage.

4.3Cut-Through IO

Cut-through IO (CTIO) is an IO accelerator for SSD arrays that boosts the throughput of devices connected to the PERC Controller. It is enabled through disabling the write-back cache (enable write-through cache) and disabling Read Ahead.

4.4Reconfiguring Virtual Disks

There are two methods to reconfigure RAID virtual disks—RAID Level Migration (RLM) and Online Capacity Expansion (OCE). RLM involves the conversion of a virtual disk to a different RAID level. OCE refers to increasing the capacity of a virtual disk, which can be accomplished in three ways:

∙If there is a single virtual disk in a disk group and free space is available, the virtual disk’s capacity can be expanded within that free space. If a virtual disk is created and it does not use the maximum size of the disk group, free space is available.

∙Free space is also available when a disk group’s physical disks are replaced by larger disks using the Replace Member feature.

∙A virtual disk's capacity can also be expanded by performing an OCE operation to add more physical disks by encompassing all available free space on a given virtual disk, adding drives and/or migrating to a different RAID level.

When a RLM/OCE operation is complete, a reboot is not necessary. For a list of RAID level migrations and capacity expansion possibilities, see Table 1. The source RAID level column indicates the virtual disk level before the RAID level migration and the target RAID level column indicates the RAID level after the operation is complete. If you configure 64 virtual disks on a controller, you cannot perform a RAID level migration or capacity expansion on any of the virtual disks. The controller changes the write cache policy of all virtual disks undergoing a RLM/OCE to Write-Through until the RLM/OCE is complete.

Note: RAID level migration and expansion is not supported on RAID levels 10, 50, and 60.

DELL PERC H700 and H800 Technical Guide 15