For upgrade...it's usually around 35-40GB. I will be doing one of my VBRs today and can let you know. 

It’s not exactly an upgrade. It’s simply a patch. Let me know versions of your upgrade please and i wil compare. Thanks.

hi ​@angel.nunez you can verify a checklist for the upgrade here

https://helpcenter.veeam.com/docs/backup/vsphere/upgrade_vbr_byb.html?ver=120

Anton Gostev starts a thread in official forums where there are some instructions for update to this patch 

https://forums.veeam.com/veeam-backup-replication-f2/veeam-backup-replication-12-3-2-4165-new-patch-delivery-options-t100568.html

The update ISO info (from https://www.veeam.com/kb4696):

name VeeamBackup&Replication_12.3.2.4165_20251006_patch.iso
Size: 1.6GB

So I think maximum 5 GB (patch size + installation file + temp space to unpackage) are needed. Please let us know to needs more 

EDIT: you start from 12.3.2 so you can apply only the EXE patch > uncompresses patch content to TEMP before installing it therefore requiring some TEMP space

VeeamBackup&Replication_12.3.2.4165_20251006_patch.zip
Size: 663 MB 

Thank you so much. As soon as I update, I will let you all know.

Good question upgrading Veeam Backup & Replication from v12.3.2.3617 to v12.3.2.4165 (Update 2a) doesn’t require a lot of extra storage, but it’s smart to have enough free space to avoid issues during installation. Keep at least 10 15 GB total free space on the server to be safe.