Configuring and Managing CacheCade Virtual Disks on a Dell PERC H710, H710P and H810 RAID Controller

This article provides information on configuring and managing CacheCade virtual disks on Dell PERC H710, H710P and H810 RAID controllers.

Table Of Contents:

1. Overview
2. Configuring and Managing CacheCade on the PERC H710, H710P, and H810
3. CacheCade Virtual Disk Characteristics
4. Configuring And Managing CacheCade Virtual Disks
5. CacheCade Virtual Disk Management
   • A. Creating CacheCade Virtual Disks
   • B. Deleting CacheCade Virtual Disks
   • C. Reconfiguring CacheCade Virtual Disks
   • D. Automatic Reconfiguration Of CacheCade Virtual Disks
   • E. Manual Resizing Of CacheCade Virtual Disks
6. Additional Information

1. Overview

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 and PERC H710 / H710P / H810 RAID controllers.

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

CacheCade Using Solid State Drives.
 
Dell OpenManage Server Administrator Storage Management User's Guide is available in the manuals section on Dell homepage.

CacheCade is used to improve random read performance of the Hard Disk Drive (HDD) based Virtual Disks. A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data. SSDs significantly increase the I/O performance (IOPS) and/or write speed in Mbps from a storage device. With Dell Storage Controllers, you can create a CacheCade using SSDs. The CacheCade is then used for better performance of the storage I/O operations. Use either Serial Attached SCSI (SAS) or Serial Advanced Technology Attachment (SATA) SSDs to create a CacheCade.
 
Create a CacheCade with SSDs in the following scenarios:

• Maximum application performance - Create a CacheCade using SSDs to achieve higher performance without wasted capacity.
• Maximum application performance and higher capacity - Create a CacheCade using SSDs to balance the capacity of the CacheCade with high performance SSDs.
• Higher capacity - If you do not have empty slots for additional HDDs, use SSDs and create a CacheCade. This reduces the number of HDDs required and increases application performance.  

The CacheCade feature has the following restrictions:

• Only SSDs with the proper Dell identifiers can be used to create a CacheCade.
• If you create a CacheCade using SSDs, the SSD properties are still retained. At a later point of time, you can use the SSD to create virtual disks.
• A CacheCade can contain either SAS drives or SATA drives but not both.
• Each SSD in the CacheCade does not have to be of the same size.
• The CacheCade size is automatically calculated as follows: CacheCade size = capacity of the smallest SSD * the number of SSDs
• The unused portion of SSD is wasted and can not be used as an additional CacheCade or an SSD-based virtual disk.
• The total amount of cache pool with a CacheCade is 512 GB. If you create a CacheCade which is larger than 512 GB, the storage controller still uses only 512 GB.
• The CacheCade is supported only on Dell PERC H700 and H800 controllers with 1 GB NVRAM and firmware version 7.2 or later, and PERC H710, H710P, and H810.
• In a storage enclosure, the total number of logical devices including virtual disks and CacheCade(s) cannot exceed 64.

Note: The CacheCade feature is available from first half of calendar year 2011.

Note: In order to use CacheCade for the virtual disk, the Write and Read policy of the HDD based virtual disk must be set to Write Back or Force Write Back and read policy must be set to Read Ahead or Adaptive Read Ahead.

2.Configuring and Managing CacheCade on the PERC  H710, H710P, and H810

The Dell PowerEdge RAID Controller (PERC) H710, H710P, and H810 cards support CacheCade, a feature that can improve application performance by increasing read caching capacity.

The CacheCade feature makes use of high performing solid state disks (SSDs) as a secondary tier of cache. CacheCade provides faster reads and maximizes transactional I/O performance.

Note: The PERC H310 does not support Cachecade.

The use of SSDs for caching allows a large quantity of data to be present in the cache, resulting in performance improvement in read-intensive applications. Some examples of read-intensive applications include online transaction processing (OLTP), file server, and web server workloads. CacheCade allows for an increase in the I/O performance of hard disk drive (HDD)-based disk groups with the assistance of SSD technology.

3. CacheCade Virtual Disk Characteristics

The following are the CacheCade virtual disk characteristics:

• Support for CacheCade virtual disks exists only on controllers containing 1 GB of Non-Volatile (NV) Cache.
• CacheCade virtual disks can only be created with SSDs.
• The maximum combined size of CacheCade virtual disks is 512 GB.

Note: Multiple CacheCade virtual disks may be created, but they are combined to operate as a single cache pool up to the maximum size.

• Data on virtual disks containing secured Self-Encrypting Disks (SEDs) or SSDs will not be cached by CacheCade.
• CacheCade virtual disks only cache input reads that are smaller than 64 KB.
• CacheCade virtual disks are read cache only.
• CacheCade virtual disks cannot be migrated to a controller that does not support CacheCade.
• Importing a CacheCade drive may result in a RAID 0 VD. You must reconfigure the CacheCade VD after importing.
• CacheCade virtual disks are not presented to the operating system. 

Note: Data on VDs with unsecured SEDs can be cached using CacheCade.

4. Configuring And Managing CacheCade Virtual Disks

After the CacheCade virtual disk is created successfully, it is listed in the Virtual Disk Management screen under the CacheCade disk group, and is labeled as a CacheCade Virtual disk. The virtual disk has an optimal state and iAll management applications allow the creation and deletion of CacheCade virtual disks.

The following sections describe the menu options specific to CacheCade virtual disk management and provide detailed instructions to perform the configuration tasks. The contents of the following section apply to the BIOS Configuration Utility (<Ctrl> <R>). For more information on the management applications, see the topic Management Applications For PERC Cards .

5. CacheCade Virtual Disk Management

The Virtual Disk Management screen is the first screen that is displayed when you access a RAID controller from the main menu screen on the BIOS Configuration Utility.

The following are CacheCade-related actions you can perform through the virtual disk management menu:

• Create CacheCade virtual disk
• Assign CacheCade virtual disk name
• Delete virtual disk

A. Creating CacheCade Virtual Disks

Note: Only SSDs can be used to create CacheCade virtual disks.

Note: Combining SAS and SATA SSDs within a CacheCade virtual disk is not supported.

Note: To avoid inefficient use of space, it is recommended that CacheCade volumes are created with drives of the same size. Larger disk sizes are truncated to the size of the smallest contributing disk, similar to RAID 0.

To create a CacheCade virtual disk:

1. During host system boot, press <Ctrl> <R> when the BIOS screen is displayed.
   The Virtual Disk Management screen is displayed. If there are more than one controller, the main menu screen is displayed.
2. Select a controller, and press < Enter>.
   The Virtual Disk Management screen is displayed for the selected controller.
3. Use the arrow keys to highlight Controller #.
4. Press <F2>.
   The list of available actions is displayed.
5. Select Create CacheCade Virtual Disk and press <Enter>.
   The Create CacheCade Virtual Disk screen is displayed. The cursor is on the first SSD listed in the Select SSD section.
6. Select the desired SSD(s). As each new SSD is selected, the CacheCade Virtual Disk Size changes to reflect the new size.

Note: You cannot specify the size of the virtual disk.

7. Press <Tab> to move the cursor to the CacheCade Virtual Disk Name field. Enter a name if required.
8. After you specify the virtual disk name, select OK to save the selection or select Cancel to cancel the selection.
   After the CacheCade virtual disk is created successfully, it is listed in the Virtual Disk Management screen under the CacheCade disk group, and is labeled as a CacheCade virtual disk. The virtual disk has an optimal state and its RAID level is RAID 0.

Note: You can only delete or rename a CacheCade virtual disk. Background initialization, fast initialization, full initialization, and consistency check operations are not applicable to CacheCade virtual disks.

B. Deleting CacheCade Virtual Disks

• To delete CacheCade virtual disks, perform the following steps in the BIOS Configuration Utility:

1. 1. Press <Ctrl> <N> to access the Virtual Disk Management screen.
2. 2. Use the arrow keys to move the cursor to the CacheCade Disk Group or Virtual Disks heading.
3. 3. Press <F2>. The Action menu is displayed.
4. 4. Select Delete VD and press .

Note: In operating system management applications, a CacheCade virtual disk deletion or removal can be done without interrupting any I/Os. The controller stops caching via the secondary cache, but all outstanding I/Os are completed.

C. Reconfiguring CacheCade Virtual Disks

In operating system management applications, the resizing of CacheCade virtual disks occurs without stopping any existing I/Os. Creating a new CacheCade virtual disk or adding one or more SSDs to an existing CacheCade virtual disk increases the total cache size. The new resources are immediately used after the addition.

There are two methods to reconfigure CacheCade virtual disks:

• Automatic reconfiguration of Cachecade virtual disks

• Manual reconfiguration of Cachecade virtual disks

D. Automatic Reconfiguration Of CacheCade Virtual Disks

A CacheCade virtual disk that is made up of more than one SSD is automatically reconfigured upon a removal or failure of a member SSD. The virtual disk retains an Optimal state and adjusts its size to reflect the remaining number of member disks. If auto-rebuild is enabled on the controller, when a previously removed SSD is inserted back into the system or replaced with a new compatible SSD, the CacheCade automatically reconfigures and adjusts its size to reflect the addition of the member SSD.

The number of SSDs to be removed from a CacheCade virtual disk cannot equal the total number of SSDs currently in the CacheCade virtual disk.

After the automatic reconfiguration and resizing of a CacheCade virtual disk, the new virtual disk size is displayed in both the BIOS Configuration Utility as well as in the OpenManage storage management application.

Note: If a disk is removed from a CacheCade virtual disk, the associated slot for that disk is a hot slot for the CacheCade volume. Any compatible disk inserted into that slot is automatically added to the CacheCade virtual disk. Any preexisting data on that drive is lost.

Note: In operating system management applications, a CacheCade virtual disk deletion or removal can Disks inserted into a CacheCade hot slot must be equal to or greater than the smallest contributing disk in the virtual disk.

E. Manual Resizing Of CacheCade Virtual Disks

In operating system management applications, a manual resizing of a CacheCade virtual disk occurs due to the addition or removal of drives. Reboot is not necessary.  

• Any number of SSDs can be added to a CacheCade virtual disk.
• There is no SAS and SATA mixing allowed within a CacheCade virtual disk, so SATA SSDs cannot be added to a SAS CacheCade virtual disk and vice versa.
• HDDs cannot be added to a CacheCade virtual disk.

Note: Capacity of drives added to a CacheCade volume must be equal to or greater than the smallest contributing drive in the virtual disk. The manual resizing of a CacheCade virtual disk cannot be initiated in the BIOS Configuration Utility. It can only be initiated in the OpenManage Storage Management application.

6. Additional Information:

Related articles and Whitepapers:

• Open Manage Storage Services (OMSS).
• Example of increasing database performance using the Dell PERC H700 with CacheCade technology.