After a volume move operation, a WAFL scan needs to be completed. The scan identifies and builds a map of relationship between logical and physical blocks (deswizzler or deswizzling). Until the scan completes, all read operations use a slower method to read data.
You can use the following commands to verify if a deswizzle process in in progress.
What is deswizzle ?
You can use the following commands Data within a FlexVol has both a logical location within the volume and a physical location within the containing aggregate. When reading data from a FlexVol, the phyical location of that data must be known to perform the read.
Under normal circumstances, reads use a fast-path to translate a logical address into a physical address. When SnapMirror transfers a FlexVol to a different aggregate, however, the relationship between logical and physical addressed is changed. The destination aggregate lays out the volume into different physical blocks. Immediately after the SnapMirror transfer, reads to the destination volume will use a different process to translate logical address into physical addresses. This slow-path is less efficient and may require an additional disk read to access a block of data. As soon as a flexvol snapmirror update finishes, the destination storage controller will launch a scanner to recreate the fast-path metadata. Once the scan finishes, reads to the SnapMirror destination will use the normal fast-path. This process is called deswizzling.
You can use the following commands to verify if a deswizzle process in in progress.
filer> priv set advanced
filer*> wafl scan status What is deswizzle ?
You can use the following commands Data within a FlexVol has both a logical location within the volume and a physical location within the containing aggregate. When reading data from a FlexVol, the phyical location of that data must be known to perform the read.
Under normal circumstances, reads use a fast-path to translate a logical address into a physical address. When SnapMirror transfers a FlexVol to a different aggregate, however, the relationship between logical and physical addressed is changed. The destination aggregate lays out the volume into different physical blocks. Immediately after the SnapMirror transfer, reads to the destination volume will use a different process to translate logical address into physical addresses. This slow-path is less efficient and may require an additional disk read to access a block of data. As soon as a flexvol snapmirror update finishes, the destination storage controller will launch a scanner to recreate the fast-path metadata. Once the scan finishes, reads to the SnapMirror destination will use the normal fast-path. This process is called deswizzling.
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