HP P2000 HP P2000 G3 MSA System SMU Reference Guide - Page 30

About the VDS and VSS hardware providers Virtual Disk Service (VDS) enables host-based applications to manage vdisks and volumes. Volume Shadow Copy Service (VSS) enables host-based applications to manage snapshots. For more information, see the VDS and VSS hardware provider documentation for your product. About RAID levels The RAID controllers enable you to set up and manage vdisks, whose storage may be spread across multiple disks. This is accomplished through firmware resident in the RAID controller. RAID refers to vdisks in which part of the storage capacity may be used to store redundant data. The redundant data enables the system to reconstruct data if a disk in the vdisk fails. Hosts see each partition of a vdisk, known as a volume, as a single disk. A volume is actually a portion of the storage space on disks behind a RAID controller. The RAID controller firmware makes each volume appear as one very large disk. Depending on the RAID level used for a vdisk, the disk presented to hosts has advantages in fault-tolerance, cost, performance, or a combination of these. NOTE: Choosing the right RAID level for your application improves performance. The following tables: • Provide examples of appropriate RAID levels for different applications • Compare the features of different RAID levels • Describe the expansion capability for different RAID levels Table 4 Example applications and RAID levels Application Testing multiple operating systems or software development (where redundancy is not an issue) Fast temporary storage or scratch disks for graphics, page layout, and image rendering Workgroup servers Video editing and production Network operating system, databases, high availability applications, workgroup servers Very large databases, web server, video on demand Mission-critical environments that demand high availability and use large sequential workloads RAID level NRAID 0 1 or 10 3 5 50 6 Table 5 RAID level comparison RAID Min. Description level disks Strengths Weaknesses NRAID 1 Non-RAID, nonstriped Ability to use a single disk to store Not protected, lower performance mapping to a single disk additional data (not striped) 0 2 Data striping without Highest performance redundancy No data protection: if one disk fails all data is lost 1 2 Disk mirroring Very high performance and data protection; minimal penalty on write performance; protects against single disk failure High redundancy cost overhead: because all data is duplicated, twice the storage capacity is required 3 3 Block-level data striping Excellent performance for large, Not well-suited for with dedicated parity sequential data requests (fast transaction-oriented network disk read); protects against single disk applications: single parity disk failure does not support multiple, concurrent write requests 30 Getting started