milvus: [Bug]: Search latency becomes high when migrating data from 1.1 to 2.1 by Milvus Data Migration Tool

Is there an existing issue for this?

• I have searched the existing issues

Environment

- Milvus version: 2.1.0
- Deployment mode(standalone or cluster): cluster
- SDK version(e.g. pymilvus v2.0.0rc2): 2.1.0
- OS(Ubuntu or CentOS): Amazon Linux
- CPU/Memory: 12C/8Gi
- GPU: 
- Others:

Current Behavior

When we migrate data from V1.1 to V2.1, we find that search latency becomes very high, from 10ms in V1.1 to 300ms+.

Data properties:

• Row count: 5.5M
• Dim 100
• Index: IVF_FLAT with nlist = 4096

Search pattern

• nq=1, topk=5, nprobe=128
• concurrency=1

Expected Behavior

Latency < 20ms

Steps To Reproduce

No response

Milvus Log

1_x_migration_0902.tar.gz

Anything else?

show_segment.txt