Reducing the cost of storage management - Backup/Restore

Computer Technology Review, Dec, 2003 by E.P. Komarla

Manageability is a top concern among IT and data center managers, for good reason: integration, deployment and operating costs can be from five to eight times the cost of hardware and software acquisition (Figure 1). Manageability involves a variety of key activities and assets such as installation, configuration, set up, asset tracking, firmware and operating system upgrades, identifying and isolating faulty servers, performing backup and restores, and managing mirror and data duplication servers.

How can manageability be improved and management costs reduced? Server and storage management can be improved at several different levels from component to server to data center. This article looks at ways of reducing storage management costs at each of these levels.

Component Integration

Increased component integration at the silicon level improves overall reliability and density of servers and storage boxes, and enables smaller form factors. Using System-on-Chip IO Processors (IOP) in Host Bus Adapters (HBA), servers and external storage boxes can significantly reduce failure rates and improve mean time between failures.

IO Processors typically include integration of:

* Core processor/s: RAID processing can be offloaded to a core processor, thus reducing the burden on the host processor and improving overall performance

* Memory controller: The IOP typically integrates a controller to maintain a large cache memory, thereby hiding latency to and from the storage disks

* PCI-X interfaces: These Peripheral Component Interconnect interfaces can be any bus interconnects. One interface is used to connect to the host bus, either initiator or target, and the other provides the capability to use standard Network Interface Controller (NIC) components

* Cyclical Redundancy Check (CRC) engine: The iSCSI specification includes a special calculation to help assure data integrity. When not performed in hardware, this calculation can be a significant burden to software and the host processor

* SATA/SAS controller: Offers low-cost RAID solutions. Drives can be directly attached to the HBA with no additional logic or controllers needed.

* XOR engine: iSCSI targets typically use RAID technology to maximize data integrity at the disks, and nearly all high performing RAID solutions use XOR in their implementations. Since XOR operations can be a large burden to software and the host processor, they are better performed in hardware.

IOPs facilitate development of single chip RAID HBA, ROMB (RAID on Motherboard), and thin form factor external storage boxes. ROMB solutions can increase the robustness and reliability in Direct Attached Storage (DAS) requiring no additional HBA or controller hardware. Typically, different RAID configurations such as RAID 0, 1, 2, 3 and 5 are supported. External storage boxes built around System-on-Chip (SoC) devices have small form factors and are designed to be cost effective.

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Storage Area Networks (SANs)

In recent years, the need to organize increasingly vast amounts of storage has created demand for a robust, scalable and manageable external storage solution. The storage area network (SAN) was designed to meet these needs. A SAN offers IT managers the ability to move storage onto a storage-specific network, where it can be consolidated and managed with tools and processes specifically designed for this purpose. Today, a majority of SANs deployed are based on Fibre Channel (FC). However, Internet SCSI (iSCSI) is emerging as a strong and low cost alternative. Figure 2 shows an iSCSI-based SAN implementation.

Both FC and iSCSI based SANs provide many of the same benefits:

* Centralized management: Promotes more efficient management and encourages sharing of documents rather than maintaining multiple duplicate copies

* More effective use of storage: By allowing for storage consolidation, these technologies typically mean fewer servers with unused capacity and fewer servers at full capacity. Instead, the servers share a pool of storage

* Higher availability: Through the use of redundancy in both SAN infra-structure components and storage components, SANs provide for higher availability than a simple server with direct-attached storage

* Faster backup and restore time: Backups can now take place on isolated networks, and since SAN traffic is block-level, data can be backed up faster than with traditional file-based backups

* Easier deployment of new capacity or load balancing of existing capacity: SANs allow for IT managers to add capacity to a single infrastructure and make it available to one or more servers without opening the server. Advanced features allow for more dynamic capabilities, including the transparent addition, deletion or movement of storage resources from one server to another

* Enabling new capabilities such as remote mirroring: Remote mirroring, snapshot copying and storage virtualization are all examples of capabilities that are enabled by the SAN