we migrated a Windows filer based on Vmware, which drew its capacity from a FAS2520, into an existing SVM (AFF300 - OS 9.8P19 incl. FlexPool/StorageGrid - V 18.104.22.168).
The videos stored there (mpeg) - on a CIFS-Volume - can no longer be loaded via the browser (Edge, Firefox as a test) if they are > 45MB in size (this works on desktop level); this also worked perfectly before the migration.
If you copy the files back to the Windows filer, this is possible again in the same browser; so it can't be due to the browser settings - right?
Are there any settings at the volume level that can/need to be adjusted?
Before making any changes to the current volume, we need to know it's current state of performance. Before the Migration, as you mentioned it was FAS2520, so was it running on hybrid aggregate (flash_pool), or regular aggregate with SAS disks or Capacity disks ? If you have a OCUM , then you could have a performance stats for last 3 to 6 months, to get an avg latency for the volume (which stored the video files).
Since, it has been migrated, is the system (Filer), has similar capacity/performance levels ? You could do QoS from CLI to understand, what's the latency like for the given volume, is there any other volume that is probably eating up most IOS from that aggregate ? Unless, there is a data to analyse it will be difficult to pinpoint the cause.
If it's a AFF300 (running ONTAP), then I can help you with few commands to get the performance data from the current volume, if it's a storagegrid, then I suggest raising a ticket with NetApp Support and work with them, they will be able to guide you on the logs they will need to troubleshoot this issue.