top tips for data center consolidation and efficiency

Blade.org © 2009 ALL RIGHTS RESERVED

Contributions for this vendor neutral technology paper have been provided by Blade.org members including NetApp, BLADE Network Technologies, and Double-Take Software.

June 2009


Introduction Blade.org has recently published two papers focused on data center efficiency beginning first with Network Consolidation and more recently Server Consolidation. The third pillar of improved data center efficiency is Storage Consolidation. Network consolidation or convergence contributes to an increased need for storage consolidation. Most companies with large IT departments may deploy or have deployed disparate storage networks including intranets, high performance computing networks, and traditional LANs. Each network may have a unique architecture and management team. Additionally, each network often has its own preferred or inherited network technology. By consolidating network technologies, greater storage consolidation is also possible by combining into one pool storage that was once dedicated to a specific network technology. Server consolidation can be achieved by shrinking server hardware as well as through server virtualization. High density servers, such as blade servers, are designed to fit many physical servers into a very small footprint. This optimization favors compute density and improved server manageability over other IT priorities, such as maximizing local storage capacity. As a result, utilizing blade servers encourages the use of networked storage. The use of server virtualization increases server density further by using a single physical server to host dozens of virtual machines. Server virtualization offers a number of benefits, including server mobility which allows load balancing of virtual machines across each physical server and enables automatic failover of a virtual machine in the event of a physical server failure. Virtual machine mobility also necessitates networked storage. Building on the discussions around network and server consolidation, this paper addresses benefits, several new technologies, and some additional items to consider when planning for storage consolidation. Whether you are considering a server or network consolidation project today or in the future, the opportunities for improved storage efficiency through increased consolidation are available to you today.


Benefits of Storage Consolidation Storage consolidation is not a new topic. Over the last two decades, storage area networks (SANs) have delivered increased storage efficiency by permitting the sharing of disk based storage across multiple servers over a shared private network or fabric. A growing trend in data center technologies is the ability to share physical resources with a variety of logical workloads, as we see with server virtualization. Moving direct attached storage (DAS) to storage systems accessed over a network offers a number of operational benefits. Capacity Sharing - Moving to networked storage improves storage utilization by allowing IT administrators to pool storage capacity and allocate it to each server as needed. In contrast, direct attached storage (DAS) is only available to the server to which it is physically attached. As a result, DAS often results in storage islands, or pools of storage capacity that can’t be shared with other servers. Once allocated to that server, it stays with that server and that server alone. Shared access to storage is the beginning of improved storage utilization. Storage Provisioning – Shared storage permits a more granular provisioning of storage capacity. LUNs or volumes can be provisioned in almost any increment, rather than being tied to the physical capacity of one or more disk drives. Additionally, volumes can be resized as capacity requirements change, without having to incur server downtime. More specific LUN provisioning reduces the wasted space commonly found in DAS environments where physical drive capacities are often much larger than the storage capacity required. Network Boot – One advantage of a storage network is the ability to not only move server data to the network, but also the server boot images. Boot volumes can be created and accessed at boot time to load the operating system image. This feature removes the requirement for any disk storage locally at the server, resulting in reduced server costs and reduced power and cooling requirements for high density environments, such as blade servers. Utilizing network boot technology, any machine can boot a different operating system image and can be quickly re-provisioned for other tasks. Server rooms, testing labs, training centers and grid computing applications can switch between boot volumes very easily. In effect, a system could be deployed with Windows® Exchange for one task and be reconfigured with Linux® and Oracle® Rack simply by changing the boot volume.


Software Updates – Updating an application image, such as a database, that is found on local storage often results in server downtime for a maintenance period. Using networked storage permits updating the application image remotely without affecting the server. The new application can then be restarted with the updated image with minimal down time. This benefit is also available for boot images. Using network boot, operating system images can be updated on the shared storage volume without disrupting the server. Once an updated image is available, the server can be rebooted using the new remote image. Performance - With the consolidation of storage from multiple servers to a single storage pool, data can be written across a larger pool of disk drives resulting in increased I/O performance. Protection - All disks on pooled storage, including boot drives, can be protected with efficient RAID algorithms and redundant storage hardware. Local storage if only used for boot volumes will typically be a mirrored pair of drives, resulting in very low storage utilization. Data paths across a storage network are typically redundant allowing access to data in the event of a cable or switch failure. Finally, networked storage is also designed with high levels of redundancy to protect against hardware failure. In contrast, DAS environments generally include multiple single points of failure at the server. Scalability – Networked storage capacity is easily expanded in large or small increments without disrupting the server. DAS environments often require opening the server to add capacity in the form of one or more disk drives. The capacity increments, in today’s disk drives, tend to be quite large. Backup and Recovery - Data backups and restores are simplified in shared storage environments. Backups can be done outside of the network, removing bandwidth requirements of the LAN. Additionally, backups can be done without the requirement of a dedicated server. Centralized backups are simple and can be done for all servers on a regular schedule without having manual intervention with each server and risk process disruption. Disaster recovery is very complicated with direct attached storage – not nearly so with pooled storage. Lifecycle Management - Pooled storage can include a variety of performance and capacity tiers in order to make sure that the most active and important data is available on the highest performing disks. Infrequently used data can be migrated in the background to slower and higher capacity disks and eventually to an archive appliance without disruption.


Operating Costs - According to the EPA, data storage devices are the fastest growing consumers of power in data centers, and rank number two in terms of power consumption next to servers1. Consolidating storage can result in fewer disk drives to store the same amount of data. Fewer disks results in lower power and cooling costs.

Table 1 Data center power consumption (Billion kWh)

Improved Management - Consolidating storage into a central pool removes many of the tasks required for individual server backup, recovery, software updates, etc. Allocation of storage to any server can be done centrally with one set of tools.

1 Report to Congress on Server and Data Center Energy Efficiency Public Law 109-431


Server and Storage Virtualization – Complementary Technologies Server virtualization and storage virtualization are very complementary technologies. In fact, storage virtualization really allows you to get the most out of your virtual server deployments. One of the primary benefits of server virtualization is the increased utilization of your server hardware, specifically the CPU. Modern servers with high performing CPUs and light workloads typically run processors between 15-20% utilized. Server virtualization enables running multiple workloads on the same server hardware and as a result, CPU utilization may increase to as much as 90% or more. Advances in storage technology are also increasing the utilization of core storage components and providing improvements in operational efficiency. The increases in storage utilization also contribute to improvements in asset utilization, the ability to defer incremental storage purchases, and positive impacts to power and cooling expenses. While traditional storage systems have enabled improvements in data center efficiency, new trends in storage virtualization are delivering unprecedented storage efficiency to large and small businesses alike. As with server virtualization, storage virtualization is enabling rapid deployment of storage resources and a dramatic increase in storage resource utilization. These benefits are accelerating business processes and removing traditional capital and operational costs. These advances couldn’t come at a better time.


New Technologies for Storage Consolidation Storage efficiency is commonly measured by how much usable storage capacity is available on a given amount of physical capacity. Due to operational and technical overheads it is rare to achieve maximum storage utilization of 100%. From an operations standpoint, IT storage administrators will provision storage with some amount of reserve space as a buffer. As mentioned earlier, inefficiencies in storage utilization in DAS environments can be reduced by sharing storage over a network, as with a SAN. However, each LUN requires some amount of reserve space. From a technical perspective, every storage system carries some amount of capacity overhead, which reduces storage efficiency to well below 100%. Items that impact storage efficiency include the RAID configuration (eg, RAID 10 requires 2x the space for data), metadata layout, how the storage controller software or firmware is stored, and even the amount of overhead from the disk manufacturers. Typical storage efficiency rates for traditional storage arrays are in the 30-40% range. That means that for every $1 you spend on storage, you may only get about 30 cents worth of usable disk capacity. You can also see that if your data is growing exponentially, that your power and cooling, and maybe even space and management expenses, will increase as well. Modern storage systems are able to deliver much higher storage utilization than previous generations. Given new advances in storage virtualization technology, storage utilization rates are often 70% or higher. In some cases, utilization over 100% can be achieved depending on the business application and type of data stored. Storage Virtualization One of the challenges with traditional storage systems is the close association between logical data blocks and physical data blocks. At the time a LUN or volume is created, the logical blocks are mapped to the physical blocks on disk. This means that at the time you provision a LUN, you must commit to that amount of disk capacity, whether you will use it right away or not. This can be expensive and inefficient. What if you never need all of the capacity you have allocated? With traditional storage, you can’t reallocate the unused space to another LUN or array that may need additional capacity. Just as server virtualization removes the dependency of virtual machines from the physical environment, modern storage systems progressively remove the dependency of storage volumes on the physical storage underneath it. These advances are delivering tremendous gains in storage efficiency and radical improvements in data management and accelerated business processes.


Thin Provisioning - Thin provisioning allows you to provision a LUN or volume without locking physical disk capacity when the LUN is created. The only time that storage is needed is when data is written onto the LUN. Thin provisioning creates a logical volume to the size the application requires, but only maps logical blocks to physical blocks on disk when data is written. Since data is rarely written to disk all at once, the physical capacity isn’t required up front. Physical capacity can be added over time, rather than in big chunks. As a result, storage can be added more effectively by following cost/capacity technology curves. Since all the physical capacity isn’t committed up front, LUNs and volumes can therefore be resized, larger or smaller, as requirements change.

Figure 1 Thin provisioning reduces LUN requirements by consolidating unused but allocated capacity. High Performance RAID 6 – As disk drive capacities continue to grow, the rebuild time of large capacity drives also continues to increase. Rebuilding a 1TB SATA drive can take hours. In a traditional RAID 5 or similar setup, this rebuild window is a time of increased exposure to a second drive failure and possible data loss. RAID 6 is an algorithm that allows for up to two simultaneous drive failures, thereby providing the additional protection during a drive rebuild. However, most RAID 6 algorithms perform


inadequately due to a significant amount of overhead processing. As a result, most vendors recommend RAID 1 or RAID 10 to protect against multiple drive failures and avoid a performance penalty. But, RAID 10 requires twice the amount of disk capacity as the data being stored, resulting in a theoretical maximum 50% raw disk utilization. And if a mirrored pair of disk drives fails, the results would be catastrophic.

Figure 2 RAID 6 improves data protection with fewer disks than alternative RAID algorithms. High performance RAID 6 technology can provide the same performance as RAID 5 and with up to a 48% reduction in disk capacity requirements versus RAID 10. High performance RAID 6 doesn’t exhibit the same risk for dual drive failures as does RAID 10. Snapshots - Space efficient snapshots can be used to take periodic point in time references to data volumes to assist in backup and recovery. Snapshots can be used to recover from data loss due to accidental deletion a file or due to a virus attack. Additionally, snapshots can be used to back up to tape or a secondary disk storage device without impacting the primary storage volume. Snapshots can be used to reduce the amount of storage required for duplicate data and provide greater flexibility for recovery options.


Data Deduplication - For primary and secondary data, deduplication can be used to reduce the data footprint of a LUN or volume. Significant savings can come from reducing duplicate backup data. Regular backups will result in large amounts of redundant data blocks. The more frequent the backups, the more redundant the data. This is referred to as temporal data, since copies of data are time based, as with a regular backup schedule. Spatial deduplication applies to standing data sets, such as primary data volumes. In this case, data blocks are compared within volumes to reduce redundant data blocks across a variety of data types. With both temporal and spatial deduplication, high levels of space savings can occur - up to 95%.

Figure 3 Deduplication significantly reduces both temporal and spatial instances of storage data. Multi-tenancy – You may have circumstances where you want to isolate data storage for security purposes. For instance, you may want to make sure that your legal or financial data is completely independent from other data such as home directories or engineering data. Another example would be if a service provider desired to keep each customer’s


data on separate storage. Often, this is accomplished by purchasing separate storage systems. Multi-tenancy allows you to create multiple logically independent storage systems that run on the same storage controller hardware. Each virtual storage system behaves much like a virtual server, in that it operates completely independently of the other virtual systems, as if it were physically isolated. This is a very effective way to get more utilization out of your storage systems without having to purchase separate hardware for each specific application.

Figure 4 Multi-tenancy enables isolation of specific workloads by virtualizing storage systems on a common hardware platform. Volume / LUN Clones - The use of space efficient volume cloning reduces capacity requirements for duplicate copies of data, such as boot volumes. Space efficient clones can be created in seconds to provide a duplicate boot environment for static and virtual servers. This feature is especially useful when updating operating system versions as well as providing centralized management for large call centers where hundreds of desktops need to be updated simultaneously. Cloning also allows for rapid server provisioning. Rapid clones can be made of a disk image and updated with new software. The server can then be quickly rebooted to access the new cloned image with the required OS updates. This feature can also improve security of the infrastructure should a virus be contracted or an upgrade goes


wrong. Normally it would take hours to recover and clean the system back to the original state but booting from SAN is easy as the server or workstation is simply recycled and the boot image is reapplied. LUN cloning permits a SAN boot image for disaster recovery and hard drive replication to be performed with the same tools used for all data management. If a machine fails, it can be directed to boot from a snapshot or copied boot volume on the SAN facilitating a faster recovery time.

Figure 5 Space efficient clones can greatly reduce storage requirements while also accelerating business processes such as test and development. Cloning is especially well suited in engineering test and development environments. Creating a copy of data to be tested often takes hours or days to create and requires a duplicate amount of disk space to hold the test data. Volume clones are space efficient like snapshots and can be created in seconds allowing for highly parallel testing and development. Solid State Disk (SSD) – Typically, the most common way to increase I/O performance is to increase the number of disk drives or spindles serving data. Solid state disks


(SSD), disks made of flash memory instead of rotating disks or platters, present an opportunity to drive significant gains in I/O performance. However, SSDs are very expensive when compared to rotating disks, around 8 to 10 times more expensive on a cost per Gigabyte. As a result, SSD adoption is primarily being considered at the high end of the market. One way to reduce the cost of SSDs is to use them with some of the features previously discussed. For instance, by using thin provisioning combined with deduplication, you can increase the effective capacity of the SSDs to a point where they are closer in price with other enterprise drives. Solid state disk technology can aid in storage consolidation by providing the desired I/O performance without the requirement of a large number of lower capacity enterprise drives. Placing a disk cache made of SSDs in front of an array of high capacity SATA disk drives can effectively deliver the I/O performance requirements of an enterprise drive array without the additional spindle count and cost associated with enterprise disks (see figure).

Figure 6 Flash technology can greatly improve performance of storage when combined with high capacity disk drives2. 2For more information, visit http://spec.org/sfs2008/results/sfs2008nfs.html. SPEC® and SPECsfs2008® are registered trademarks of the Standard Performance Evaluation Corporation.

http://spec.org/sfs2008/results/sfs2008nfs.html


Storage Consolidation – Before You Start Traditionally, storage migration is complex, time-consuming and expensive due to data centers having disparate hardware that requires manual configuration and the need for data and application downtime. Often, IT personnel are trapped in the data center, after hours, to make sure of the success of the migration. There are better options utilizing a combination of virtualization and SAN based or host based replication technologies that are hardware-independent. Moving storage workloads can be simplified for administrators while also minimizing the impact on user productivity. If you don’t have time to migrate, many technologies are available that can continuously capture data changes from a server’s OS and application and replicate those changes to new more efficient storage. Whether using synchronous or asynchronous replication, data blocks that change are moved using minimum bandwidth and can allow for scheduling of the transfer process. This process permits greater control with respect to how much bandwidth migration operations consume. An additional benefit of this methodology is that during the migration, users always have access to data and the associated applications so there is little or no downtime. Migrations can take place during business hours - reducing or eliminating after hours data migration projects. LUN Migration and Storage Flexibility - Utilizing storage with virtualization platforms can help provide workload flexibility across storage devices regardless of the storage vendor. This combination of storage and virtualization provides flexibility to move the workloads, where SAN resources are more readily available, in real-time whenever needed. This coordination helps build on underlying dynamic infrastructure to make use of existing infrastructure to easily move between storage devices either in a primary data center or satellite location. DAS to Shared Network Storage Native OS Boot - When migrating from DAS to a network boot environment, you must first evaluate the scale of the deployment. Architects must consider how many hosts will boot over the shared storage controller and include the applications that will be in production. Depending on the type of technology that is deployed, SAN or NAS, differences in efficiencies that are gained between methodologies exist. Typically NAS or iSCSI deployments can be less expensive because of the opportunity to repurpose hardware and training. Conversely, FC booted environments typically provide greater security at a higher cost. With the advent of converged networks, the administrator can take advantage of multiple technologies on the same physical hardware. For example


an administrator could use iSCSI to boot a system’s OS via thin provisioned LUN clones and attach to files via NFS all while utilizing the same physical network. Network boot can enable a server to be provisioned and re-provisioned quickly. Servers gain instant flexibility by separating the operating system and data from the hardware. Additionally, after a server has been re-provisioned the boot volume it was previously mapped to can be repurposed back into the pool of available storage. iSCSI - Some small or medium size businesses look for solutions that can turn any Windows or Linux server with direct attached storage into an iSCSI SAN to help provide a cost effective solution while using their existing infrastructure. This type of storage flexibility provides shared modes for the iSCSI storage it manages, allowing multiple servers or workstations to access data. When used with a system that leverages network boot, it also allows for rapidly launching and provisioning of servers, both virtual and physical, as well as desktops, for recovery, migration, consolidation or backup. All this is possible using a combination of traditional host-based technologies and new iSCSI storage based technologies. NFS / CIFS - As businesses migrate from local disks to shared storage, files can be accessed as CIFS shares or NFS mounts, transparent to the end user. Common use cases for this methodology include client “home” directories in which an employee’s data is stored on network storage thereby taking advantage of the backup, redundancy, and availability benefits already mentioned. Summary With the ever expanding data growth of today’s modern businesses, the ability to store, manage, protect, and retain digital data is ever more challenging. Consolidating data storage offers a number of benefits to improve the manageability and reduce the cost of storage assets. Even greater efficiencies can be achieved with the use of modern data storage features, such as deduplication and cloning. Combined with network consolidation and server consolidation with blade servers and virtualization, data centers can greatly reduce the burdens associated with data growth and expanding data center requirements. About Blade.org Blade.org functions as a collaborative source of expertise on deploying blade solutions and provides a trusted voice in the IT marketplace. Blade.org’s vendor members are actively working together to help businesses harness the major trends that Blade.org believes will define the new enterprise data center. Some of the key topics prominently taking center stage at Blade.org include advanced energy efficiency, network convergence and hyper-consolidation. Visit www.blade.org for more information.

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top tips for data center consolidation and efficiency

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