Sparse bundle

.sparsebundle to .backupbundle (for TimeMachine macOS 10.15)

While both sparse images and sparse bundles contain a file system, a sparse bundle is bundle-backed, meaning that it employs a specialized, hierarchical directory structure for grouping related resources. Within a sparse bundle, the bands subdirectory contains the actual data saved within the disk image.

Change band size:

hdiutil convert -format UDSB -imagekey sparse-band-size=262144 -o new.sparsebundle old.sparsebundle
# Will take lot of time ~ hours

The sparse-band-size parameter is the number of 512-byte sectors (chunks), not the number of bytes. Since 512 is 1/2 1,024, then 262,144 B / 2 = 128 KiB.

Where 262144 equals 128MB bands/byte sectors (128 MBytes == 128*1024*1024 bytes == 128*1024*1024/512 blocks = 262144 blocks, 262144 / 2 / 1024 = 128MB)

Read it:

hdiutil info -verbose | grep band-size
# Or accessible in Info.plist in the .sparsebundle

Copy sparse bundle

If it's block level incremental backup (BLIB) or if the rsync algorithm is used for unencrypted sparse bundle, the band size is not important, smaller size you should be considered for the traffic impact

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