Introduction to storage virtualization
This chapter defines the concept of storage virtualization and provides an overview about how to apply virtualization to address the challenges of storage requirements. It includes the following topics:
1.1 Storage virtualization terminology
Storage virtualization is a term that is used extensively throughout the storage industry. It can be applied to various technologies and underlying capabilities. In reality, most storage devices technically can claim to be virtualized in one form or another. Therefore, this chapter starts by defining the concept of storage virtualization as it is used in this book.
IBM describes storage virtualization in the following way:
•Storage virtualization is a technology that makes one set of resources resemble another set of resources, preferably with more desirable characteristics.
•It is a logical representation of resources that is not constrained by physical limitations and hides part of the complexity. It also adds or integrates new function with existing services and can be nested or applied to multiple layers of a system.
When the term storage virtualization is mentioned, it is important to understand that virtualization can be implemented at various layers within the I/O stack. There must be a clear distinction between virtualization at the disk layer (block-based) and virtualization at the file system layer (file-based).
The focus of this publication is virtualization at the disk layer, which is referred to as block-level virtualization or the block aggregation layer.
The Storage Networking Industry Association’s (SNIA) block aggregation model provides a useful overview of the storage domain and the layers, as shown in Figure 1-1. It illustrates several layers of a storage domain:
•File
•Block aggregation
•Block subsystem layers
Figure 1-1 SNIA block aggregation model1
The model splits the block aggregation layer into three sublayers. Block aggregation can be realized within hosts (servers), in the storage network (storage routers and storage controllers), or in storage devices (intelligent disk arrays).
The IBM implementation of a block aggregation solution is IBM Spectrum Virtualize software, running on IBM SAN Volume Controller and IBM Storwize family.
The IBM SAN Volume Controller is implemented as a clustered appliance in the storage network layer. In contrast to that, the IBM Storwize family is deployed as modular storage that provides capabilities to virtualize its own internal storage and potentially external storage.
The IBM Spectrum Virtualize software can also be deployed as a software-defined storage solution on third-party x86-based platforms. However, that topic is beyond the intended scope of this publication. For more information, see Implementing IBM Spectrum Virtualize software only, REDP-5392.
The key concept of virtualization is to decouple the storage from the storage functions that are required in the storage area network (SAN) environment.
Decoupling means abstracting the physical location of data from the logical representation of the data. The virtualization engine presents logical entities to the user and internally manages the process of mapping these entities to the actual location of the physical storage.
The actual mapping that is performed depends on the specific implementation, such as the granularity of the mapping, which can range from a small fraction of a physical disk up to the full capacity of a physical disk. A single block of information in this environment is identified by its logical unit number (LUN), which is the physical disk, and an offset within that LUN, which is known as a logical block address (LBA).
The term physical disk is used in this context to describe a piece of storage that might be carved out of a Redundant Array of Independent Disks (RAID) array in the underlying disk subsystem. Specific to the IBM Spectrum Virtualize implementation, the address space that is mapped between the logical entity is referred to as a volume. The array of physical disks is referred to as managed disks (MDisks). The combination of several managed disks is referred to as a Storage Pool.
Figure 1-2 shows an overview of block-level virtualization.
Figure 1-2 Block-level virtualization overview
The server and application are aware of the logical entities only. They access these entities by using a consistent interface that is provided by the virtualization layer.
The functionality of a volume that is presented to a server, such as expanding or reducing the size of a volume, mirroring a volume, creating an IBM FlashCopy®, and thin provisioning, is implemented in the virtualization layer. It does not rely in any way on the functionality that is provided by the underlying disk subsystem. Data that is stored in a virtualized environment is stored in a location-independent way, which enables a user to move or migrate data between physical locations, which are referred to as storage pools.
IBM Spectrum Virtualize software provides the following benefits:
•Online volume migration while applications are running, which is possibly the greatest single benefit for storage virtualization. This capability enables data to be migrated on and between the underlying storage subsystems without any effect on the servers and applications. In fact, this migration is performed without the knowledge of the servers and applications that it even occurred.
•Simplified storage management by providing a single image for multiple controllers, and a consistent user interface for provisioning heterogeneous storage.
•Enterprise-level Copy Services functions. Performing Copy Services functions without the dependencies on the storage subsystems. Therefore, it enables the source and target copies to be on other storage subsystem types.
•Storage usage can be increased by pooling storage across the SAN.
•System performance is often improved with IBM Spectrum Virtualize and IBM Storwize V7000 as a result of volume striping across multiple arrays or controllers and the other cache that it provides.
•Software-based encryption capabilities to provide improved data security among storage virtualization solutions.
•Data replication to cloud storage using advanced copy services for data migration and backup solutions.
•Data reduction techniques for space efficiency such as Thin Provisioning and compression.
IBM Spectrum Virtualize software delivers all these functions in a homogeneous way on a scalable and high availability software platform over any attached storage and to any attached server.
1.2 Requirements driving storage virtualization
Today, many organizations are searching affordable and efficient ways to store, use, protect, and manage the data. An emphasis is put on the IBM Cognitive era of clients’ businesses and their dynamic infrastructure. Therefore, a storage environment requires an easy to manage interface and flexibility to support many applications, servers, and mobility requirements.
The following key client concerns drive storage virtualization:
•Growth in data center costs
•Inability of IT organizations to respond quickly to business demands
•Poor asset usage
•Poor availability or service levels
•Lack of skilled staff for storage administration
You can see the importance of addressing the complexity of managing storage networks by applying the total cost of ownership (TCO) metric to storage networks. Industry analyses show that storage acquisition costs are only about 20% of the TCO. Most of the remaining costs relate to managing the storage system.
But how much of the management of multiple systems, with separate interfaces, can be handled as a single entity? In a non-virtualized storage environment, every system is an “island” that must be managed separately.
1.2.1 Benefits of using IBM Spectrum Virtualize
IBM Storwize V7000 running IBM Spectrum Virtualize software, reduces the number of separate environments that must be managed down to a single modular environment. It also provides a single interface for storage management and various functions. After the initial configuration of the storage subsystems, all of the day-to-day storage management operations are typically performed by using the graphical user interface of IBM Spectrum Virtualize. For the storage provisioning automation using for example orchestrator applications, a command line interface with secured access is also available.
Because IBM Spectrum Virtualize provides many functions, such as mirroring and IBM FlashCopy, there is no need to acquire additional subsets of applications for each attached disk subsystem that is virtualized by IBM Spectrum Virtualize.
Today, it is typical that open systems run at less than 50% of the usable capacity that is provided by the RAID disk subsystems. The use of the installed raw capacity in the disk subsystems shows usage numbers of less than 35%, depending on the RAID level that is used. A block-level virtualization solution, such as IBM Spectrum Virtualize, can allow a significant increase to approximately 75 - 80%.
With IBM Spectrum Virtualize, free space does not need to be maintained and managed in each storage subsystem, which further increases capacity usage.
1.3 Latest changes and enhancements
IBM Spectrum Virtualize V7.3 and its related hardware upgrade represented an important milestone in the product line development, with further enhancements in V8.1. The internal architecture of IBM Spectrum Virtualize software is significantly rebuilt, enabling the IBM Storwize V7000 system to break the previous limitations in terms of scalability, flexibility, availability, and functionality.
The intent of this book is to cover the major software changes and provide a brief summary of supported hardware.
1.3.1 IBM Storwize V7000 Gen2+
IBM Storwize V7000 Gen2+ model is a modular, virtualized, enterprise-class storage solution technology. Each IBM Storwize V7000 module is delivered in 2U 19-inch rack-mounted enclosure. The IBM Storwize V7000 can be easily managed by using a web-based graphical user interface, and it provides a number of functions and features.
The control enclosure features two redundant controllers combined into a cluster with single management. Each controller contains one 8-core Intel Xeon processor with 32 GB or 64 GB of cache: One hardware compression accelerator card and an additional slot for the second accelerator.
A front view of the IBM Storwize V7000 Gen2 and Gen2+ is shown in Figure 1-3.
Figure 1-3 Front view of IBM Storwize V7000 Gen2 and Gen2+
Similar to the previous version, the IBM Storwize V7000 Gen2+ base model comes as a 2U- 19-inch rack-mounted enclosure. Each controller features one 10-core Intel Xeon processor with 32 GB memory cache and optional cache upgrade to 64 GB. IBM Storwize V7000 Gen 2+ comes by default with an integrated hardware compression card to support IBM Real-time Compression™ workloads.
IBM Storwize V7000 Gen 2 and Gen2+ support 1-Gb iSCSI connectivity as standard with options for 16-Gb Fibre Channel and 10 Gb for iSCSI and FCoE connectivity.
IBM Storwize V7000 Gen2 is referred as model 524 and Gen2+ as 624. In this publication, both models are referred to as only IBM Storwize V7000.
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Note: For a comprehensive list of supported configurations, see IBM Storwize V7000 configuration limits and restrictions at:
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1.3.2 IBM Spectrum Virtualize Software changes and enhancements
This section provides an overview of the relevant software enhancements incorporated to the IBM Storwize V7000 code. We do not provide enhancements made in previous versions of the code (V5.x and V6.x) as they are already well known to the market and widely used by administrators.
At the V7.3 announcement, IBM included the following changes:
•IBM Easy Tier® version 3, including storage pool balancing within the same tier and extent migration across any two adjacent tiers in a three tier storage pool. This function is enabled automatically in IBM Spectrum Virtualize software and does not need any licenses.
•New cache architecture. Advanced cache algorithm splits the original single cache into upper and lower caches. The upper cache provides cache partitioning and fast write response times as it is the highest I/O stack layer. The lower cache provides a number of cache functions to support destage, read caching, and prefetching.
At V7.4, IBM announced the following changes:
•The most noticeable change in V7.4 after the first login is the modified graphical user interface (GUI) with the new layout of the system window. The enhanced functions are available directly from the welcome window.
•The concept of the GUI design conforms to the well-known approach from IBM System Storage XIV® Gen3 and IBM FlashSystem® 840. It provides common, unified procedures to manage all these systems in a similar way, enabling administrators to simplify their operational procedures across all systems.
•Child pools are new objects that are created from the physical storage pool and provide most of the functions of managed disk groups (MDiskgrps), such as volume creation. However, the user can specify the capacity of the child pool at creation.
•A new level of volume protection prevents users from removing mappings of volumes that are considered active. Active means that the system has detected recent I/O activity to the volume from any host within a protection period that is defined by the user. This behavior is enabled by system-wide policy settings. The detailed volume view contains the new field that indicates when the volume was last accessed.
•A user can replace a failed flash drive by removing it from the expansion enclosures unit and installing a new replacement drive, without requiring a Directed Maintenance Procedure (DMP) to supervise the action.
•The user determines that the fault light-emitting diode (LED) is illuminated for a drive, so they can expect to be able to reseat or replace the drive in that slot. The system automatically performs the drive hardware validation tests and promotes the unit into the configuration if these checks pass.
•Additional enhancements to T10 Data Integrity Field for the data stored on drives for IBM Storwize Gen2.
•Improved performance of Real-time Compression by double I/O operations per second (IOPS) on the model 2145-DH8 and 2076-524 (when it is equipped with both Compression Accelerator cards). It introduces two separate software compression engines (RACE), taking advantage of multi-core controller architecture. Hardware resources are shared between both RACE engines.
At the V7.5 announcement, IBM included the following changes:
•Direct host attachment by using 16 Gbps FC adapters with all operating systems except IBM AIX.
•Support for Microsoft Offloaded Data Transfer (ODX).
•Introduction of IBM HyperSwap® topology. It enables each volume to be presented by two I/O groups. The configuration tolerates combinations of node and site failures, using a flexible choice of host multipathing driver interoperability.
•Support of VMware vSphere V6.0 virtual volumes (VVol). Each virtual machine (VM) keeps different types of data each in a VVol, each of which is presented as a volume (logical unit is SCSI) by the IBM Spectrum Virtualize system. Therefore, each VM owns a small number of volumes.
At V7.6, IBM announced the following changes:
•Visual and functional enhancements in the GUI, with changed menu layout and an integrated performance meter on main page.
•Implementation of Distributed RAID, which differs from traditional RAID arrays by eliminating dedicated spare drives. Spare capacity is spread across disks, making the reconstruction of failed disk faster.
•Introduced software encryption enabled by IBM Spectrum Virtualize and using AES256-XTS algorithm. Encryption is enabled on the storage pool level. All newly created volumes in such pool are automatically encrypted. An encryption license with Universal Serial Bus (USB) flash drives is required.
•Developed the IBM Comprestimator Utility, which is included in IBM Spectrum Virtualize software. It provides statistics to estimate potential storage savings. Available from the CLI, it does not need compression licenses and does not trigger any compression process. It uses the same estimation algorithm as an external host-based application, so results are similar.
•Enhanced GUI wizard for initial configuration of HyperSwap topology. IBM Spectrum Virtualize now allows IP-attached quorum disks in HyperSwap system configuration.
•Increased the maximum number of iSCSI hosts attached to the system to 2048 (512 host iSCSI qualified names (IQNs) per I/O group) with a maximum of four iSCSI sessions per SVC node (8 per I/O group).
•Improved and optimized read I/O performance in HyperSwap system configuration by parallel read from primary and secondary local volume copies. Both copies must be in a synchronized state.
•Extends the support of VVols. Using IBM Spectrum Virtualize, you can manage one-to-one partnership of VM drives to IBM Storwize V7000 volumes. It eliminates single, shared volume (data store) I/O contention.
•Customizable login banner. Using CLI commands, you can now define and show a welcome message or important disclaimer on the login window to users. This banner is shown in GUI or CLI login window.
At V7.7, IBM announced the following software changes:
•Introduction of new software capabilities to support encryption protection of data stored in D-RAID volumes.
•Enhanced external virtualization flexibility to support iSCSI-based external storage virtualization.
•IP Link compression algorithm to improve usage of IP networks, which reduces the volume of data that must be transmitted during remote copy operations.
•GUI support for IP Quorum to help administrators to configure the IBM Storwize V7000 in a HyperSwap solution using IP Quorum solution.
•GUI support for Comprestimator to assist administrators use the compression functions to display thin provisioning and compression estimates analysis for single or multiple volumes.
•Each clustered system can support up to 10,000 volumes.
With V7.8, IBM incorporated the following innovative changes:
•GUI support for Cloud Storage. In V7.8, IBM introduced software capabilities to interface the IBM Spectrum Virtualize to an external cloud storage service provider. This functionality is priced as additional per software code.
•Support for Dense Drawer that provides rack-mounted high-density disk expansion enclosures that connects by using SAS to Storwize V7000 enclosures. Each 5U Dense Drawer can support up to 92 drives.
•Extended support for additional Tier 1 solid-state drives (SSD). The IBM Spectrum Virtualize software features new attributes to manage Read Intensive SSDs. An alert is logged in the system event log when the drive endurance reaches 95%.
•Improved security by extending the encryption capabilities to software that complies with the Key Management Interoperability Protocol (KMIP), such as IBM Security Key Lifecycle Manager (SKLM).
•Increased flexibility to support IBM Storwize V7000 model conversion to enable clients to convert existing systems to more powerful models.
V8.1 introduces the following features and enhancements:
•Redesigned management GUI to conform to the look and feel of other strategic IBM products.
•IBM Spectrum Virtualize in IBM Storwize V7000 Gen2+ now offers up to 128 GB of cache per canister.
•IBM Storwize V7000 now contains a software toolset that can establish a secured tunnel connection to the Remote Support Server that sits in an IBM internal network and collects health and troubleshooting information for support personnel. The associated Health Checker provides customized, rules-based configuration recommendations at no additional cost.
•Storing encryption keys to up to four external key servers (SKLM) that can standby with each other in case of a single key server failure. Storwize V7000 supports co-existence of USB keys and external key servers.
•Pause capability in concurrent code upgrade enables flexibility during code updates.
•IBM SAN Volume Controller (SVC) and Storwize Family delivers an additional option with a 900 GB 15 K RPM 2.5-inch SAS drive.
•Discontinued support of first generation of Storwize V7000 models in V8.1 (models 1xx, 2xx, 3xx). These models are supported up to V7.8 until their effective hardware End of Support date.
1.4 Summary
The use of storage virtualization is the foundation for a flexible and reliable storage solution that helps enterprises to better align business and IT by optimizing the storage infrastructure and storage management to meet business demands.
IBM Spectrum Virtualize running on IBM Storwize V7000 Gen2 and Gen2+ is a mature, nine-generation virtualization solution that uses open standards and complies with the SNIA storage model. The IBM Storwize V7000 is a powerful modular storage, in-band block virtualization process in which intelligence (including advanced storage functions) is ported from individual storage devices to the storage network.
IBM Spectrum Virtualize can improve the usage of the storage resources, simplify the storage management, and improve the availability of business applications.
1 Source: Storage Networking Industry Association.
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