Navisphere Command Line Interface (CLI) Reference - VMware Communities

Reserved LUN Pool CommandsEstimating the reserved LUN pool sizeEach reserved LUN can vary in size. However, using the same sizefor each LUN in the pool is easier to manage because the LUNs areassigned without regard to size; that is, the first available free LUN inthe global reserved LUN pool is assigned. Since you cannot controlwhich reserved LUNs are being used for a particular replicationsession, we recommend that you use a standard size for all reservedLUNs.If you want to optimize space utilization, the recommendation wouldbe to create many small reserved LUNs, which allows for sessionsrequiring minimal reserved LUN space to use one or a few reservedLUNs, and sessions requiring more reserved LUN space to usemultiple reserved LUNs. On the other hand, if you want to optimizethe total number of source LUNs, the recommendation would be tocreate many large reserved LUNs, so that even those sessions whichrequire more reserved LUN space only consume a single reservedLUN.Estimating a suitable reserved LUN pool sizeThe following considerations should assist in estimating a suitablereserved LUN pool size for the storage system.◆◆◆If you wish to optimize space utilization, use the size of thesmallest source LUN as the basis of your calculations (seepage 356). If you wish to optimize the total number of sourceLUNs, use the size of the largest source LUN as the basis of yourcalculations (see page 356).If you have a standard online transaction processingconfiguration (OLTP), use reserved LUNs sized at 10-20%. Thistends to be an appropriate size to accommodate thecopy-on-first-write activity.If you plan on if you plan on creating multiple sessions per sourceLUN, anticipate a large number of writes to the source LUN, oranticipate a long duration time for the session, you may also needto allocate additional reserved LUNs. With any of these cases, youshould increase the calculation accordingly. For instance, if youplan to have 4 concurrent sessions running for a given sourceLUN, you might want to increase the estimated size by 4 – raisingthe typical size to 40-80%.355