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Synthetics Overvier Definitions – Catalog – Image – Extent Process Overview (today) – Extent map derivation – Read agenda – Data movement – Validate completed image Virtual Synthetics – Implementation OST Virtual Synthetics 2

Definitions (For Synth Puproses) Catalog – Database of backup metadata – Backups known to Netbackup, location on media – Files within a backup, including location and size Image – Container for backup data – Whole backup or part; one or more fragments Extent – Representation of data chunk within a backup – Block offset into backup and number of blocks in length – Blocks are 512 bytes OST Virtual Synthetics 3

Extent Map Derivation This is a catalog operation – Looks back through recent history of backups for a given policy. – Develops a combination of full + incrementals necessary to synthesize a new backup. – Uses file metadata of incremental backups to determine files added, replaced, or deleted after the full backup. – Extent mapping is derived by choosing most recent instance of a file. Results in: – A set of extents mapped to backup id. – Extent set for most recent backup is first, oldest is last – Extent list is in block ascending order for each backup. – Overall extent list is ordered by how the extents should appear in the resulting backup OST Virtual Synthetics 4

Read Agenda Synthetics today allows read from any backup on any media server and write to any media server. – Heterogeneous capability provides value with costs – Tape read/write strategy results in sequential extent reading and writing. Synth reprocesses the extent mapping – Chooses source copy and maps source media – Extents may be divided to reflect fragmentation. Read agenda is based on extent sets for each media – One reader for each backup on each media OST Virtual Synthetics 5

Data movement and Validation Writer is launched, targeting new media with a new backup id Readers are launched synchronously: – Each reader will read large contiguous extents of the source image. – The reader filters the data read according to the extent mapping for the backup. – Passes data to the writer via a socket. When all readers and the writer is done, new image is marked complete. – This signals to the rest of Netbackup that the image is ready for restores, duplication, and future synthetics. Presentation Identifier Goes Here 6

Virtual Synthetics Goals – Produce synthetic backups with little or no copying involving a NBU data mover – A fully virtual image would involve linking data in existing images into a new image. Uses stsp_include_in_image(). – Make synthetics a metadata operation rather than a data movement. – Cheapen “synthetics forever” Realizations – On-disk organization is driven by capability of the storage server. Allows storage servers to bring their value to the Netbackup equation. – Inferred relationship given by stsp_include_in_image() could be used to perform better SIS. – Virtual images can be used to re-organize existing images (alternative views) OST Virtual Synthetics 7

Virtual Synthetics Realizations (con’t) – Synth to 2nd storage server could be a local synth plus optimized duplication – Extents in new image can be ordered based on need rather than data movement. Implementation – Source images and target LSU must be on the same storage server. – Storage server advertises “include in image” support. – Netbackup detects this capability and uses it to dynamically choose whether to use a virtual synthetic operations or default to the traditional non-virtual synthetic backup. – Extent mapping and read agenda are constructed similarly to the non- traditional synthetic backup method. OST Virtual Synthetics 8

Virtual Synthetics Implementation (con’t) – Target image is constructed sequentially. – Source images are opened as needed. – The “include in image” operations are performed by one Netbackup media server. – Resulting image should be identical and indistinguishable from an image constructed using the non-virtual method. OST Virtual Synthetics 9

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