LCP : Dynamic Management (increase and decrease) of Safeguarded Capacity

This idea would benefit all IBM z customers who are using, or who are considering implementing Logical Corruption Protection (aka z Cyber Vault) of data hosted on DS8000 storage subsystems.

It would be of particular value to large installations who may be close to reaching the virtual limit for provisioned space on the DS8000; those with very volatile workloads, where logical devices (ldevs) are frequently added to, or moved between SMS Storage groups; or in sites where a lot of consolidation is taking place.

Our request is for more dynamic management of Safeguarded Capacity (SGC) to be made available in the DS8000. Specifically, and in priority order :

1.       Dynamic expansion of an ldev’s SGC multiplier should take place immediately, and not have to wait for any existing ‘gated’ backups to expire. This is a key point if RPO targets are to be met, as the warnings issued today do not necessarily allow enough time to make the required multiplier changes before copies are dropped – even if this were to be done automatically by GDPS or other management software.

2.       Allow dynamic reduction of the SGC multiplier for selected ldevs -i.e. this should take place without having to delete any existing safeguarded backups. This is key to ensuring that the virtual limits of allocated space on the DS8000s are not reached.

3.       Remove the device-level SGC multiplier altogether and instead manage safeguarded capacity in pools – like virtual versions of the physical extent pools that exist in the DS8000 today. Again, we would need to be able to dynamically increase and decrease the size of these SGC pools.

Item (1) would require a ‘reduce’ equivalent of all ‘expandsafeguardedcapacity’ commands or tools that are in place today – e.g   DSCLI, DS8000 messages, the device manager on z, IDCAMS, ICKDSF etc, as well as any APIs used by GDPS, CSM or other tools like CA-Vantage.

Item (2) would require no changes from the user’s perspective, as all changes would be in the background on the DS8000.

For item (3), the virtual SGC pools could be displayed and managed using the same tools that are currently employed to look after extent pools – possibly including a background or user-scheduled task that puts freed-up capacity back into the pool.