我正在尝试使用cassandra压力测试我的3个cassandra（3.11.3.5）集群节点。目前我正在运行3个节点和一台机器，其中cassandra工具正在运行，所有东西都在openvpn网络上。
我已经在这里创建了我的.yaml用户配置文件测试文件：

### DML ###

# Keyspace Name

keyspace: mykeyspace

# The CQL for creating a keyspace (optional if it already exists)

keyspace_definition: |
  CREATE KEYSPACE mykeyspace WITH replication = {'class': 'NetworkTopologyStrategy', 'DC1': '2'}  AND durable_writes = false;

# Table name

table: mytable

# The CQL for creating a table you wish to stress (optional if it already exists)

table_definition: |
  CREATE TABLE mytable (
    id bigint, 
    type int,
    txt text,
    event_datetime timestamp,
    bigtxt text,    
    page int,
    PRIMARY KEY ((id, type), page, event_datetime)
  ) WITH CLUSTERING ORDER BY (page DESC, event_datetime DESC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = 'ciao'
    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 90000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';

### Column Distribution Specifications ###

columnspec:
  - name: id
    size: gaussian(1..1000)       
    population: gaussian(1..500k)  

  - name: type
    size: gaussian(0..5)
    population: gaussian(1..5)

  - name: event_datetime
    cluster: fixed(1)         

  - name: page                  
    size: ~exp(1..20)
    population: ~exp(1..20)
    cluster: fixed(1)

  - name: txt
    size: exp(30..1k)

  - name: bigtxt
    size: gaussian(10k..30M)    

### Batch Ratio Distribution Specifications ###

insert:
  partitions: fixed(1)            # Our partition key is the domain so only insert one per batch

  select:    fixed(1)/1        

  batchtype: UNLOGGED             # Unlogged batches

queries:
   pages:
      cql: select id, page, type, txt, event_datetime, bigtxt from mytable where id = ? and type = ? and page=? limit 10;
      fields: multirow

到目前为止，我运行的命令是对此命令的修改：

cassandra-stress user n=30 profile=./myprofile.yml ops\(insert=1\) -rate threads=10 -node 10.5.0.1,10.5.0.6,10.5.0.8

我改变了什么：
n
线程计数
旧油门
已用固定
我总是犯一些错误，比如：

com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: 10.5.0.1/10.5.0.1:9042 (com.datastax.driver.core.exceptions.OperationTimedOutException: [10.5.0.1/10.5.0.1] Timed out waiting for server response), 10.5.0.6/10.5.0.6:9042 (com.datastax.driver.core.exceptions.OperationTimedOutException: [10.5.0.6/10.5.0.6] Timed out waiting for server response), 10.5.0.8/10.5.0.8:9042 (com.datastax.driver.core.exceptions.OperationTimedOutException: [10.5.0.8/10.5.0.8] Timed out waiting for server response))

我在变暖阶段也发现了这些错误。
运行结果如下：

Results:
Op rate                   :        0 op/s  [insert: 1 op/s]
Partition rate            :        0 pk/s  [insert: 1 pk/s]
Row rate                  :        2 row/s [insert: 3 row/s]
Latency mean              : 38172.3 ms [insert: 38,172.3 ms]
Latency median            : 37279.0 ms [insert: 37,279.0 ms]
Latency 95th percentile   : 59190.0 ms [insert: 59,190.0 ms]
Latency 99th percentile   : 59458.5 ms [insert: 59,458.5 ms]
Latency 99.9th percentile : 59458.5 ms [insert: 59,458.5 ms]
Latency max               : 59458.5 ms [insert: 59,458.5 ms]
Total partitions          :         30 [insert: 30]
Total errors              :          0 [insert: 0]
Total GC count            : 2
Total GC memory           : 3.396 GiB
Total GC time             :    0.2 seconds
Avg GC time               :  117.0 ms
StdDev GC time            :    0.0 ms
Total operation time      : 00:01:04

我不能理解的是：
为什么延迟时间和我跑步时得到的完全不同 nodetool cfhistograms mykeyspace mytable 在节点上？在节点上，我得到大约200毫秒的延迟，99%的写入时间。可能与cassandra工具向协调器发送mbs数据所花费的时间有关？
为什么我看不到在cassandra工具命令中更改throttle/fixed rate开关的任何效果？我总是得到1个op/s
如果我有一个生产集群（如测试集群），即使它接收到更重的混合工作负载（大约3小时内读取600k次，写入1m次），但没有这些错误，为什么我会经常遇到前面的错误？