Building Blocks for Optimal Storage Design

    Storage architecture and design for VMware can become complex if not well planned and well thought out. To determine optimal storage design for VMware, following considerations need to be taken into account. All VMware features have a direct impact on how a storage infrastructure needs to be designed and architected. Cost, Capacity and Performance are also important points to consider while creating a storage layout for VMware. A “Cost Conscious”, peak performing scalable design is possible as long as all aspects of the design are understood. Some aspects of an Optimal Storage Design include the bare minimum design possible to create a functioning VMware infrastructure based on minimum configuration requirements and how scalable the design is.

The Bare Minimum Storage Design

    The “Bare Minimum Storage Design” is the minimum configuration essential for a functioning storage array. Bare minimum storage configurations are obviously very limited in terms of capacity, bandwidth and performance. If an application requires fully redundant, higher performance and higher capacity storage I/O, bare minimum storage configuration may not be an ideal choice. Sun Storage bare minimum configuration will support all VMware features. Following is the absolute bare minimum Sun Storage configurations supported with VMware and VMware features:

If there is a need to use Sun Storage Bare Minimum configurations for VMware environments, following best practices are recommended for optimal integration.

Disk and RAID layout

    With the limited number of disk drives available in the bare minimum Sun Storage array, choosing the right RAID type is essential. In order to take maximum advantage of a 5 disk configuration, all five disk drives should be of the same type and capacity. One drive needs to be designated as a Spare in case of a drive failure. With four remaining drives, there are limited options on choosing a RAID Group based on Cost, Capacity and Performance. For example, RAID-5 will provide available capacity of 3 out of the 4 disks with space equal to one disk used for parity stripes. RAID-1 will allow for usable space of upto two drives with the remaining two drives used for mirroring and decreased performance. RAID-0 will offer the most available space with usable capacity of all four drives, however, with no redundancy built in.Table-2 below provides general comparison of different RAID types for cost, capacity, performance and availability.

Designing for Maximum Performance

    Performance can be enhanced at multiple levels of Sun Storage arrays. However, with bare minimum configurations, there are two most common components which can have a higher impact. Controller Cache and disk drives. Depending on the type of I/O, one or the other or both may need to be optimized. For heavy sequential Reads, larger cache is recommended with cache pre-fetch enabled for optimal performance. The cache pre-fetching feature allows intelligent data block placement into cache prior to an I/O request based on past read requests, hence enhancing read performance. The higher the amount of cache, the more data can be pre-fetched into cache at a given time. In addition to larger cache, if high performance storage I/O is a key requirement for a given configuration, Sun Storage arrays can be configured with high performance SAS or Fibre Channel drives. For capacity and other SAS and Fibre Channel drive specifications, refer to www.sun.com/storage.

Volume Layout for VMware

    For optimal VMware volume layout configuration on a Sun Storage bare minimum configuration, it is recommended that only VMFS volumes be used. VMFS takes complete advantage of all VMware features including VMware level snapshots and Storage VMotion which would be an ideal tool for data migration if and when additional storage arrays are added to the bare minimum layout. Following recommendations should be followed if a bare minimum Sun Storage array is being configured for VMware:

• Follow Virtual Machine sizing recommendations outlined in this document
• Create a volume or a lun on the array equal to, or larger than, the sizing calculation for Virtual Machine home directories and use VMware to create VMFS filesystem on this volume or lun. This space will be used to create Virtual Machines and their home directories
• If needed and necessary, create a volume or lun for ISO images which can be shared with ESX servers to install operating systems on Virtual Machines, applications and updates without the need for a cdrom drive on the servers and having to physically replace CDs as needed.
• Create subsequent volumes or luns for user/application data as necessary for each Virtual Machine, ideally two to three volumes or luns based on application/data type.

Source/Kaynak : http://blogs.sun.com/saidsyedblog/entry/sun_storage_sizing_and_design1