kafka有个broker一直在同步分区，I/O已经满负荷

kafka 2.12-2.3.1
9台虚机 16C 32G 12T
每台主机1块盘

配置：

broker.id=5
num.network.threads=8
transaction.state.log.replication.factor=3
num.partitions=6
offsets.topic.replication.factor=3
default.replication.factor=3
num.io.threads=8

有个broker突然失联，然后一直同步失效分区，同步了1天，上面的kafka-zk也显示无法对外服务：

This ZooKeeper instance is not currently serving requests

该broker主机执行命令很卡，state-change.log一直在打日志，server.log日志里面有以下异常和warning：

WARN Attempting to send response via channel for which there is no open connection, connection id xxx
WARN [ReplicaFetcher replicaId=5, leaderId=1, fetcherId=0] Error in response for fetch request
WARN [ReplicaFetcher replicaId=5, leaderId=9, fetcherId=0] Partition xxx marked as failed (kafka.server.ReplicaFetcherThread)
Shrinking ISR from 2,5 to 5. Leader: (highWatermark: 0, endOffset: 0). Out of sync replicas: (brokerId: 2, endOffset: -1). (kafka.cluster.Partition)

初步怀疑是因为只有1块盘，I/O系统已经满负荷，磁盘可能存在瓶颈，关停这个broker后，zk恢复正常，I/O负载正常

监控报表如下：

请问讲应用全部停止后，等分区全部同步完成再启动应用，能否恢复？

实在不行，打算提供个更大规模的集群，每台主机多块盘