IBM BladeCenter PS703 Technical Overview And Introduction

Also see for BladeCenter PS703: Service guide

Contents

76 IBM BladeCenter PS703 and PS704 Technical Overview and IntroductionKeep the following considerations in mind when planning BladeCenter S basic local storageimplementations: Every blade requiring integrated storage connectivity must have one SAS ConnectivityCard installed. At least one DSM must be installed into the BladeCenter S chassis; a maximum of twoDSMs are supported in one chassis. The IBM BladeCenter S does not ship with anyDSMs as standard. At least one SAS Connectivity Module must be installed into the BladeCenter S chassis. Amaximum of two SAS modules are supported for redundancy and high availabilitypurposes.If two SAS connectivity modules are installed, the module in I/O module bay 3 controlsaccess to storage module 1, and the module in I/O module bay 4 controls access tostorage module 2. Each physical hard disk drive in any DSM can be assigned to the one blade server only,and the blade itself sees this physical disk (or disks) as its own hard disk drives connectedvia SAS expansion card. That is, there are no LUNs, storage partitions, and so forth as inshared storage systems. Instead, each blade has its own set of physical disks residing inDSM (or DSMs). The SAS Connectivity Module controls disk assignments by using zoning-like techniques,which results in the SAS module maintaining single, isolated, dedicated paths betweenphysical HDDs and the blade server. Configuration of HDD assignments is done by theadministrator, and the administrator uses predefined templates or creates customconfigurations. The RAID functionality is supplied by the onboard SAS controller when SAS ConnectivityCards are used in the blade servers. The maximum number of drives supported by the IM volume is two, plus one optionalglobal hot spare. The IME volume supports up to ten HDDs plus two optional hot spares.The IS volume supports up to ten HDDs. The IS volume does not support hot sparedrives. When creating a RAID-1 array, we recommend that you span both disk storage modules.This maximizes the availability of data if one of the paths to the disks is lost, because thereis only one connection to each disk storage module, as shown in Figure 2-30 on page 75. Mixing HDDs of different capacities in a single volume is supported. However, the totalvolume size is aligned with the size of the smallest HDD, and excess space onlarger-sized HDDs is not used.Supported combinations of volumes include:– Two IM or IME volume per blade server– One IM or IME volume and one IS volume per blade server– Two IS volumes per blade server Each blade with an SAS expansion card has access to its assigned HDDs in both DSMs,even if only one SAS Connectivity module is present. Potentially, all 12 drives in bothDSMs can be assigned to the single blade server. However, only 10 HDDs can be used ina single volume. You can create either two volumes to utilize the capacity of all drives, ordesignate the remaining two drives as hot spares. Both SAS and SATA hot swap HDDs are supported, and an intermix of SAS and SATAdrives is supported, as well. However, each volume must have hard disks of the sametype; that is, SAS or SATA. External disk storage attachments are not supported.