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When configuring a NetVault SmartDisk Storage Pool, you can identify it as a favorite for specific roles (favour), and you can indicate that it should never be used for specific roles (deny). |
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Using the volume-size parameter, you can set aside a portion of the volume so that it cannot be used for NetVault SmartDisk. After the volume is full with NetVault SmartDisk or non-NetVault SmartDisk data, NetVault SmartDisk will not store anything else on the volume until space is made available. |
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NetVault SmartDisk uses storage space in each volume up to a threshold amount that includes space directly set aside using the volume-size parameter, and the Last Resort Threshold (LRT) amount set by NetVault SmartDisk internally. |
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NetVault SmartDisk first uses a volume for its intended role, for example, Chunk Store or Staging Store, but it also uses it for other purposes if necessary. Even if you supply a threshold, NetVault SmartDisk implements an LRT that stops NetVault SmartDisk from using a volume after there is less than a certain amount of space available and thus prevents the disk from becoming full. The LRT is calculated to include both a fixed amount of space (1 GB) and the space that would be required to make Garbage Collection possible, that is, the gc_reserve_bytes parameter. This situation means that the figure varies in size depending on the amount of data held in the Chunk Store; typically, you can expect the gc_reserve_bytes parameter to be at least 1.7 GB. |
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If the LRT is large enough, NetVault SmartDisk properly allocates space when multiple Staging Store and Chunk Store processes are both writing to a volume that becomes too full. NetVault SmartDisk maintains an overall idea of how much space is used both by the Staging Store and the Chunk Store. This idea allows it to enforce the LRT and the volume-size limits. |
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User thresholds and the NetVault SmartDisk LRT do not affect licensing. Licensing measures the amount of data accepted for protection by the NetVault SmartDisk Instance, regardless of whether the data has been deduplicated. |
Consider the following guidelines when assigning NetVault SmartDisk Storage Pool Roles:
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Content Index: Should be small and reside in a Storage Pool made of fault-tolerant disks with good random-access performance. |
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Staging Store: Should reside in a Storage Pool made of fault-tolerant disks with good streaming performance. |
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Chunk Index: Should reside in a Storage Pool made of fault-tolerant disks with good random-access performance. |
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Chunk Store: Should reside in a Storage Pool made of fault-tolerant disks. |
Also, Linux, UNIX, and Mac OS X systems support use of the noatime feature for file systems, usually as a mount option. Quest recommends that you enable this feature on your system to improve NetVault SmartDisk performance, especially for the Chunk Index and Chunk Store volumes. Using this feature can reduce the number of metadata writes required to update read-access times for files.
On Windows platforms, you can disable the New Technology File System (NTFS) Last Access Update feature, which can reduce disk accesses and increase performance. For instructions on disabling this feature, see the documentation for your specific OS.
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