This article describes what happens during the first roll-up for each account on a platform that has been upgraded from V5 to V6. Note that what happens will depend on whether your backup clients have also been upgraded to V6 or whether they are still on V5.
Backup Clients on V5 vs Backup Clients on or V6
The difference in a rollup for a V5 client and a V6 client is the global data store. If a client is still on V5 the rolled-up files remain isolated to the account and are not moved to the global datastore. On a V6 account the global datastore is used, utilizing global SIS.
Disk space required
The disk space required for the first rollup after an upgrade is usually much more than any other roll-up (both while still using the V5 Platform or for later roll-ups on the upgraded V6 platform). The reason for this is that all files touched by the roll-up will be re-encrypted from Blowfish to AES. This once-off operation requires an extra copy of all processed files for the account to be temporarily stored on disk. The space requirement can however never be higher than the OnDisk value for the account, so as a rule of thumb you should always more free space available than the account with the largest OnDisk value to successfully complete the first roll-ups after an upgrade. (Note that on any one StorageServer only one roll-up is ever done at a time).
As an example, if a Backup Account has an OnDisk usage of 50GB you need at least an extra 50GB of free disk space to be be able to perform the first roll-up. Thereafter the disk space requirements will be less (the same as on V5 or most likely less due to deduplication).
When a roll-up fails or is cancelled for some reason (perhaps the StorageServer is restarted), the rolled-up files remain on disk so that when the roll-up is retried it will resume from the last successful file. This means that a StorageServer with many aborted roll-ups will require even more disk space. As soon any the roll-up is completed the extra disk space used by that account is however released as the old Blowfish encrypted files are removed.
Processing time required for the first roll-up
Similary, the first roll-up for each account after upgrading the SP to V6 will take significantly longer in most cases. The reason for this is again because all V5 files (Blowfish) must be re-encrypted to V6 format (AES). Remember that on a V5 Storage Platform only changed files were processed during a roll-up (month end); all other files were simply moved. However, in V6 these unchanged files have to be re-encrypted and that takes extra time. Note that this is fortunately a once-off process and will not be required with every roll-up.
Implications of keeping a Backup Client on V5
There are disadvantages in keeping a Backup Client on V5 as opposed to upgrading it to V6: