Dell PowerVault MD3200i Series Technical Manualbook

Also see for PowerVault MD3200i Series: Manual Update Rack Installation Instructions User guide Support Matrix

Contents

Dell PowerVault MD3200i Series Technical Manualbook Manual pdf 33 page image

DELL PowerVault MD3200i/MD3220i Technical Guide Book31SnapshotThe MD3200i series of arrays Snapshot functionality providesan additional level of data protection and the means toimprove production data utilization. Snapshot enables non-production servers to access an up-to-date copy of productiondata for a variety of applications – including backup,application testing, or data mining – while the production dataremains online and user-accessible.A snapshot is a point-in-time image of a source virtual disk. Itis the logical equivalent of a complete physical copy, but iscreated much more quickly and requires less disk space.Snapshots appear and function as standard virtual disks; theyare host-addressable and can be read, written to or copied.Snapshot uses an innovative copy-on-write technology tomaintain the logical snapshot virtual disk while minimizingdisk utilization. When the snapshot is “taken,” the controllersuspends I/O to the source virtual disk for a few seconds whileit creates a new physical virtual disk – called the repository virtual disk – to store snapshot metadataand copy-on-write data. When a data block on the source virtual disk is modified, a copy-on-writeoccurs, copying the contents of blocks that are to be modified into the repository virtual disk forsafekeeping. This repository virtual disk combined with the original source virtual disk creates thelogical snapshot virtual disk.Since the only data blocks that are physically stored in the repository virtual disk are those that havechanged since the time of the snapshot, the snapshot technology uses less disk space than a fullphysical copy. The repository virtual disk is typically 20 percent of the base virtual disk, but will varydepending on the amount of changes to the data. The longer a snapshot is active, the larger therepository is needed. Virtual disk snapshot provides notification when the repository virtual disk nears auser-specified threshold (a percentage of its full capacity). And at any time, the volume expansionfeature can be used to dynamically expand the repository virtual disk.Virtual Disk CopyThe MD3200i series of arrays Virtual Disk Copy functionality provides administrators with another toolto effectively manage information growth and maximize the utilization of the storage array. Virtualdisk copy creates a complete physical copy, or a clone, of a virtual disk within a storage array. Theclone virtual disk is a unique entity that can be assigned to any host and used by applications requiringa point-in-time (PiT) copy of production data – such as backup,application testing or development, information analysis ordata mining – without affecting the performance of theproduction virtual disk.Virtual disk copy is configured and accessed via easy-to-usewizards. It supports up to eight concurrent copies taking placewithin a single array. Virtual disk copy is a backgroundoperation with five user-defined priority settings, enablingadministrators to minimize either copy time or the overall I/Oimpact to the storage system. As virtual disk copy is controllerS o u r c eV i r t u a lD i s kP h y s i c a lS n a p s h o tV i r t u a lD i s kS n a p s h o tR e p o s i t o r yL o g i c a lB a s eV i r t u a ld i s kV i r t u a ld i s kC o p yP i TC l o n e