We have an azure search instance(s1, 2 replica, 2 Partitions) created in 2016, and when I tried to upload 50 million rows to this instance, we found out that the old instance still has a limit of 30million records.
No problem, I created a new azure search instance (s1, 1 replica, 1 Partition), and start to upload the same data up. To my surprise, the uploading speed is much better on the new instance comparing to the old one (almost double the update speed).
I am wondering what could be the reason? The index I was uploading to is a new index, so no one will query it. These are the differences I can see between new and old search index:
Just very curious on why I see such a speed difference. If I run a search query, actually, the performance will be very similar between old and new. Just the index update speed is much much better.
Query traffic is a factor, but it could also be the replica count. Every replica adds work to the indexing process, while every partition adds to the parallelism available for indexing. If you added a partition to your new service and indexing sped up further, that wouldn't be a surprising result.
All that said, the most likely explanation in your case is that your new service is running on faster hardware than the old one. This is how we were able to remove the document limit for new services.