best practice from Netapp for separate datastores

02 Aug

from the horse’s mouth:
VMware environments deduplicate extremely well. However, while working out the VMDK and data store layouts, keep the following points in mind: Operating system VMDKs deduplicate extremely well because the binary files, patches, and drivers are highly redundant between virtual machines (VMs). Maximum savings can be achieved by keeping these in the same volume. Application binary VMDKs deduplicate to varying degrees. Duplicate applications deduplicate very well; applications from the same vendor commonly have similar libraries installed and deduplicate somewhat successfully; and applications written by different vendors don’t deduplicate at all. When deduplicated, application data sets have varying levels of space savings and performance impact based on application and intended use. Careful consideration is needed, just as with nonvirtualized environments, before deciding to keep the application data in a deduplicated volume. Transient and temporary data such as VM swap files, pagefiles, and user and system temp directories do not deduplicate well and potentially add significant performance pressure when deduplicated. Therefore NetApp recommends keeping this data on a separate VMDK and volume that are not deduplicated. Data ONTAP 7.2.6 and 7.3.1 introduce a performance enhancement referred to as intelligent cache. Although it is applicable to many different environments, intelligent caching is particularly applicable to VM environments, where multiple blocks are set to zero as a result of system initialization. These zero blocks are all recognized as duplicates and are deduplicated very efficiently. The warm cache extension enhancement provides increased sequential read performance for such environments, where there are very large amounts of deduplicated blocks. Examples of sequential read applications that benefit from this performance enhancement include NDMP, SnapVault, some NFS-based application, and dump.

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Posted by on August 2, 2010 in Uncategorized


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