With the push to consolidate servers, minimize footprint, and reduce power and cooling costs using VMware Inc.'s brand of virtualization well under way, the next generation of users have turned their attention to VMware's storage capabilities. This chapter of our VMware ESX Server
runbook includes tips and advice on setting up and maintaining virtual storage systems. Follow the linked items to learn about storage on VMware ESX.
|CHAPTER 1: Networking configurations and considerations|
|CHAPTER 2: ESX Server management||CHAPTER 3: Managing storage in an ESX Server environment||CHAPTER 4: Scripts for streamlining VMware ESX|
The advantages of storage virtualization have become clearer to VMware and non-VMware shops: Virtualization abstracts the storage image from physical storage and results in fewer disruptions in your data center. But VMware admins need to understand the particulars of storage on ESX.
Storage VMotion changes the storage game
The addition of Storage VMotion to the VMware ESX Server 3.5 portfolio changes the storage game, especially for storage virtualization vendors miffed by Storage VMotion's release. Touted as a major feature of ESX Server 3.5, the new services enables VMware administrators to migrate guest OS virtual disks from one data store to another while the virtual machine (VM) is running.
The Storage VMotion breakthrough comes with some minor gotchas, though. For instance, Storage VMotion can only be used through the VMware Remote CLI (RCLI), which translates to a GUI-less operation. Second, it is unclear whether Storage VMotion users will encounter into any VMFS defragmentation issues, considering that Virtual Machine Disk Formats, or VMDKs, can be moved around contiguously.
The good news is that the VMware community has responded with tips for adding a GUI to Storage VMotion. Further, of the two methods currently available, at least one doesn't break ESX Server compatibility rules. More plug-ins may become available, as well as possible disk de-fragmentation tools specifically for VMware.
Storage VMotion is only one attempt to remedy what many enterprise data center managers see as a weakness in ESX. And despite updates to backup software products and VMware ESX, most users continue to struggle with storage in virtual server environments because of compatibility and storage vendor support.
SAN connections on ESX
Storage VMotion is only one consideration in the upper part of the ESX stack. Underneath, virtualization administrators must also have an understanding of storage components such as Virtual Machine File System (VMFS), logical unit numbers (LUNs) and storage area networks (SANs), as infrastructures continue to become virtualized. In particular, it's become a necessity to have the know-how to troubleshoot SANs in data centers' virtual environment. This is because SAN storage is a superior solution for the virtualized environment when administered correctly.
Despite being agreed upon as the best storage option for backing up virtualized infrastructure, your data center may opt not to use SANs. Reasons may include set up costs and isolated connectivity. But options are available for getting remote data centers for virtual environments without SAN replication.
Part of implementing SAN storage in a virtualized environment involves working with LUNs and metaLUNs. Windows and Linux server admins can expand their partitions into free space, ESX administrators cannot. But there are working methods for ESX administration with VMFS and metaLUNs. In the VMware world, a volume is similar to a Windows or Linux partition. A VMFS-2 volume can be extended onto a new SCSI device, or LUN, with the VMFS tools command line utility, vmkfstools.
Storage and backup with VMware and SAN depend on connectivity. Until recently, VMware ESX didn't support iSCSI. But this changed in ESX 3.0.2 when combined with VMware Consolidated Backup (VCB) 1.0.3. When boning up on storage on ESX, one of the first tasks VMware administrators should master is how to configure ESX and VCB for use with iSCSI.
Videocast: The next steps of storage virtualization
If you'd like to hear more about storage virtualization, check out this videocast: The next steps of storage virtualization. You'll learn how to calculate an ROI for a virtualization project, where to begin testing virtualization, the best approach for choosing a virtualization solution, when to refrain from virtualizing storage, what the future holds for virtualization and more.
For other storage- and virtualization-related mediacasts, check out our research library.
This was first published in April 2008