VMware ESX Server Optimization with EMC® Celerra®

Version 1



    Optimizing ESX Server for use with different storage devices is a common question, and this syndicated EMC document provides a good mix of technical knowledge, practical advice and test results.


    This document is syndicated from a technote on EMC.com, which means it has been selected by the VIOPS expert community as a document of value to the community for reference by VIOPS, while the technote itself remains on emc.com.


    In this document you will find key information from the EMC technote, including the outline of the document, the introduction and the summary.  For the detail of the report, a link is provided to the source EMC technote.


    Intended Audience


    For use by VMware Certified Professionals (VCP) and Storage Management professionals, when considering the architecture of a VMware Infrastructure solution, and/or analysing the performance for possible optimization and improvement.




    • VMware ESX Server with Celerra NFS and iSCSI overview

    • Optimization performance study

    • Celerra uncached mechanism

    • Celerra prefetch mechanism

    • Virtual machine alignment

    • ESX Server read/write buffer size for NFS

    • ESX Server iSCSI initiators

    • Performance study details

    • Performance study conclusion

    • Appendix A: Workload specifications information

    • Appendix B: Using the Celerra uncached write mechanism

    • Appendix C: Using the Celerra prefetch read mechanism

    • Appendix D: Aligning virtual machines provisioned from Celerra storage


    VMware ESX Server with Celerra NFS and iSCSI overview


    VMware™ ESX Server, the key component of the VMware Virtual Infrastructure virtualization suite, supports Network File System (NFS) and Internet Small Computer Systems Interface (iSCSI) storage provisioning.


    iSCSI is a transport protocol for sending SCSI packets over TCP/IP networks. The iSCSI architecture is based on the client/server model in which an iSCSI host system (client) encapsulates SCSI packets through an iSCSI initiator and sends them to a storage device (server) through an iSCSI target. Similar to Fibre Channel storage, storage provisioning of iSCSI storage in ESX Servers is accomplished by creating a Virtual Machine File System (VMFS) datastore that contains iSCSI logical unit numbers (LUNs) that are configured on the iSCSI storage system.


    NFS is a file-based network access protocol that works well with the file encapsulation concept inherent to the Virtual Infrastructure suite. This leads to key advantages in provisioning, backup, and management of Network Attached Storage (NAS) with Virtual Infrastructure (version 3.x). NFS storage is provisioned in ESX Servers by creating a NAS datastore using an NFS export that is defined in the NFS storage system.


    The Celerra® Network Server provides support for NFS and iSCSI storage that can be provisioned simultaneously to ESX Servers across the virtual data center. In addition, the Celerra provides support for CIFS and Fibre Channel.

    See the VMware ESX Server Using EMC Celerra Storage System Solutions Guide for information about using VMware with Celerra NFS and Celerra iSCSI.


    Optimization performance study


    A study was conducted to understand the performance of ESX Server using storage provisioned from Celerra. For NFS, a Celerra file system was provisioned to ESX Server and configured as a NAS datastore. For iSCSI, a Celerra iSCSI LUN was provisioned to ESX Server and configured as a VMFS datastore.


    This study explored the use of the following two performance-related Celerra mechanisms and configuration options:


    • Uncached mechanism

    • Prefetch mechanism


    This study also assessed the impact of using Celerra Replicator™ to remotely replicate the Celerra file system provisioned to ESX Server in conjunction with these two Celerra mechanisms.


    Furthermore, this study explored the use of various ESX Server configuration alternatives in conjunction with Celerra as follows:


    • Virtual machine alignment

    • NFS buffer size tuning

    • iSCSI initiator alternatives with ESX Server


    Performance study conclusion


    Based on the results of this study, the following recommendations should be considered when using VMware in a Celerra environment:


    1. Use the uncached option on Celerra file systems provisioned to the ESX Server as NAS datastore. This can improve the overall performance of the virtual machines. This should be considered particularly with random and mixed workloads that have write I/O.

    2. When using random and mixed workloads without replication, consider disabling prefetch on the Celerra file system. This can improve the overall performance of virtual machines provisioned with Celerra NFS storage.

    3. Align virtual machines that are provisioned with Celerra iSCSI storage as it can improve the overall performance of the virtual machines.

    4. Do not align virtual machines that are provisioned with Celerra NFS storage because this may degrade the overall performance of the virtual machines.

    5. Consider using an iSCSI HBA on the ESX Server with sequential workloads with Celerra iSCSI storage. This can improve the overall performance of virtual machines with such workloads.


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