Question & Answer
Question
This technote provides details on how to use Tape Optimized Recalls to speed up recall process of HSM migrated files from sequencial storage.
Cause
Recalling data from sequential storage can be challenging. The recall process may appear to hang because of the recall session being in MediaW state. This can happen for example when the needed volume is already in use by another recall. The tape optimized recalls is designed to speed up the recall with the following :
- Avoids frequent tape mount and unmount operations.
- Avoids excessive tape seek operations.
- Enables tape drives to go to streaming mode, if possible, for optimal performance. Streaming mode is possible only if the recalled files are located contiguously on the tape.
- Orders and recalls files in separate steps so that you can restrict the recall operations on certain tapes.
- Can recall files from several tape drives in parallel to increase recall throughput.
Answer
The Tape Optimized Recall consists of the following two (2) steps :
1. Generate optimized order list
2. Recall with input of the order list
Step 1.
Use preview option to generate a list for all needing recalls from a filesystem. For example :
dsmrecall -p /hsm_fs
Use the -filelist option if only certain file need to be recalled. For example :
dsmrecall -p -filelist=/hsm_recall_file_list /hsm_fs
The contents of /hsm_recall_file_list would be similar to what follows :
/hsm_fs/dir1/file1
/hsm_fs/dir/file2
/hsm_fs/dir3/file3
For example :
dsmrecall -p -filelist=/hsm_recall_file_list /hsm_fs
...
TSM Server query successfully finished.
Starting file list ordering ...
10 file lists successfully ordered for tape optimized recall.
Output collection list created : /hsm_fs/.SpaceMan/tapeOptimizedRecall/7/2193818/filelist.ordered.collection
Total number of files to recall : 6582
Total number of bytes to recall : 1244905052
Notes :
The generated list is stored in /hsm_fs/.SpaceMan/tapeOptimizedRecall/node_ID/PID/
The name of the is filelist.ordered.collection
In above example, the list name is hsm_fs/.SpaceMan/tapeOptimizedRecall/7/2193818/filelist.ordered.collection
Step 2.
Run the below command to start the recall of files :
dsmrecall -filelist=/hsm_fs/.SpaceMan/tapeOptimizedRecall/nodeID/PID/filelist.ordered.collection /hsm_fs
For above example, the command to do tape optimized recall is:
dsmrecall -filelist=/hsm_fs/.SpaceMan/tapeOptimizedRecall/7/2193818/filelist.ordered.collection /hsm_fs
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Document Information
Modified date:
18 June 2018
UID
swg21649211