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A Method of Allocating Disk Space for a Logical Partition (LPAR) Request

IP.com Disclosure Number: IPCOM000218084D
Publication Date: 2012-May-18
Document File: 5 page(s) / 164K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method of allocating disk space for a Logical Partition (LPAR) request is disclosed. The method efficiently selects Logical Unit Number (LUN) masked disks to satisfy a requested amount of disk space.

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A Method of Allocating Disk Space for a Logical Partition (LPAR) Request

Disclosed is a method of efficiently selecting Logical Unit Number (LUN) masked disks to satisfy a requested amount of disk space for a Logical Partition (LPAR) request. When a request is made for an LPAR of a file system of a particular size, the file system is provisioned by selecting multiple LUN masked disks such that the sum of their sizes is at least the size of the file system requested.

The method is elucidated through the algorithm in Figure 1, r is the value that a user has requested for the size of a volume group in the LPAR provision. L is a list of all the available LUN disk sizes at runtime. pickedDisks is the list of LUN sizes to use to fulfill a volume group request of size r . s represents the sum of all of elements currently in

pickedDisks or

                        . An upper bound on what is allowed to be provisioned, for a size of r is denoted by maxThreshold . tempThreshold is what may be referred to as the "tentative upper bound". A condition

is valid at any point during the execution of the

LPAR request. The default value of tempThreshold is the same value as r and it may be continually incremented whenever no LUN size combination exists such that

               . If tempThreshold reaches the value of maxThreshold and still no valid combination of LUNs is found, the algorithm learns that no LUN combinations exist to satisfy the request. currentDisk represents the current disk in L that is being tested to check if it may be added to pickedDisks . The amount of disk space that is yet to be accounted for on a given iteration of the algorithm is represented by diskLeft . The amount of disk space that has been accounted for on a given iteration of the algorithm
is represented by diskAllocated.

Figure 1

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Section 1 in Figure 1 outlines preliminary steps necessary for execution of the algorithm. First, a value for the requested volume group size as well as a name of the volume group to be provisioned is passed to the algorithm. Subsequently, a list of available LUN sizes is assembled and sorted. First decision made by the algorithm is whether or not the volume group to be provisioned will be for the volume group rootvg that holds a base operating system. Best practices in LPAR provisioning avoid disk mirroring on rootvg, and as a result of the best practice rootvg comprises a single LUN. If this disk request is for rootvg, then the algorithm simply loops through the sorted list of LUNs and provisions the first one that is larger than the requested disk space. If this disk request is not for rootvg, then the algorithm calculates its upper bound threshold on provisioning disk space for this request maxThreshold . maxThreshold may be calculated by adding a smallest available LUN that exists in the environment (minDisk) to the requested size for the volume group (r ) such that the provisioned volume group may over estimate its request by, at most, the small...