Question & Answer
Question
What is the purpose of the LBProtect option that became available with Tivoli Storage Manager server 6.2.4.0 and 6.3.1.0? Is there any trade off that comes with the option?
Answer
LBProtect provides added protection against SAN network corruption (bad switch, hba, etc.). If you have experienced corruption in your SAN network before, or need to be extra sure that the data is valid, then this feature becomes viable. This feature was provided to satisfy customers doing long term archives, wanting to make sure the data's integrity was in tact through the whole data path.
For this, you could have CRC checking between client and server, and this feature between server and tape drive. The LBProtect option is basically equivalent to CRC checking (along with some performance degradation) but instead of client to server it is server to tape drive.
Unless you have experienced SAN network corruption or want CRC checking to validate data at the cost of backup/restore performance, you probably wouldn't enable, especially if you have a copy storage pool in place already. In case you want to enable it, you might want to go about using this slowly and/or selectively to make sure the performance degradation isn't noticeable). In most environments, just a secondary copy is sufficient.
At the time of this writing, this feature is specific to LTO5 and 3592 gen4 and above for both lines of HW. Some non-IBM hardware might be adding this feature too, as it was added to the SCSI standard recently.
The intent of LBProtect is not necessarily a debugging tool, and it isn't currently designed to be easily toggled back and forth but intended as a long term setting. APAR IC91615 has been opened recently to document an issue with objects spanning volumes, so called continuation volumes. if new volumes attributes do not match the preceding volumes attributes. Under this condition, an error message like the following is thrown and the operation gets aborted:
ANR9999D_4274045281 SinkStore(ssswtr.c:2462) Thread<939>:
Incompatible continuation volume: supported: True:False,
reserved: 48:0, blkSize: 262144:0
To prevent from this condition, the APAR documents the following local fix:
update all volumes in the affected storage pool with status filling to readonly before changing the LBPROTECT option:
UPDate Volume * ACCess=READOnly WHEREDEVclass=<DEVC> WHERESTatus=FILling
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Modified date:
17 June 2018
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