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Every time OpenZFS takes a snapshot it creates on-disk block pointer objects (bpobj's) to track blocks associated with that snapshot. In common use cases most of these bpobj's are empty, but the number of bpobjs per-snapshot is proportional to the number of snapshots already taken of the same filesystem or volume. When a single filesystem or volume has many (tens of thousands) snapshots these unecessary empty bpobjs can waste space and cause performance problems. OpenZFS waits to create each bpobjs until the first entry is added to it, thus eliminating the empty bpobjs. | Every time OpenZFS takes a snapshot it creates on-disk block pointer objects (bpobj's) to track blocks associated with that snapshot. In common use cases most of these bpobj's are empty, but the number of bpobjs per-snapshot is proportional to the number of snapshots already taken of the same filesystem or volume. When a single filesystem or volume has many (tens of thousands) snapshots these unecessary empty bpobjs can waste space and cause performance problems. OpenZFS waits to create each bpobjs until the first entry is added to it, thus eliminating the empty bpobjs. | ||
Note: The <tt>empty_bpobj</tt> feature flag must be enabled to take advantage of this. | |||
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