redis version:2.0.4
Java client for redis: http://code.google.com/p/jredis/
随机产生一个10个字节的字符串key,value与key相同，写入redis,当数据量达到1900w时，出现了如下的一些状况：刚开始测试程序全部写入db0,后来修改了测试程序，均匀写入其它数据库
master上面的日志信息：
[457] 25 Mar 11:35:58 - DB 0: 18308251 keys (0 volatile) in 50331648 slots HT.
[457] 25 Mar 11:35:58 - DB 1: 61384 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 2: 61203 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 3: 61195 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 4: 61227 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 5: 61208 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 6: 61207 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 7: 61218 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 8: 61189 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 9: 61223 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 10: 61179 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 11: 61361 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 12: 61227 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 13: 61231 keys (0 volatile) in 65536 slots HT.
[457] 25 Mar 11:35:58 - DB 14: 30792 keys (0 volatile) in 32768 slots HT.
[457] 25 Mar 11:35:58 - DB 15: 30590 keys (0 volatile) in 32768 slots HT.
slave开启来后，在slave的redis.log日志记录里看到如下的报错信息：
[15029] 25 Mar 11:33:20 * Connecting to MASTER...
[15029] 25 Mar 11:33:20 # Bad protocol from MASTER, the first byte is not \'$\', are you sure the host and port are right?
[15029] 25 Mar 11:33:21 * Connecting to MASTER...
[15029] 25 Mar 11:33:21 # Bad protocol from MASTER, the first byte is not \'$\', are you sure the host and port are right?
[15029] 25 Mar 11:33:22 * Connecting to MASTER...
[15029] 25 Mar 11:33:22 # Bad protocol from MASTER, the first byte is not \'$\', are you sure the host and port are right?
[15029] 25 Mar 11:33:23 * Connecting to MASTER...
[15029] 25 Mar 11:33:23 # Bad protocol from MASTER, the first byte is not \'$\', are you sure the host and port are right?
这个报错信息不太友好，host与port肯定是对的
查看slave的info信息：slave与master一直同步失败,同步到547w数据的时候就挂掉了
redis> info
redis_version:2.0.4
redis_git_sha1:00000000
redis_git_dirty:0
arch_bits:64
multiplexing_api:epoll
process_id:15029
uptime_in_seconds:933
uptime_in_days:0
connected_clients:1
connected_slaves:0
blocked_clients:0
used_memory:1006633016
used_memory_human:960.00M
changes_since_last_save:0
bgsave_in_progress:0
last_save_time:1301023746
bgrewriteaof_in_progress:0
total_connections_received:1
total_commands_processed:1
expired_keys:0
hash_max_zipmap_entries:64
hash_max_zipmap_value:512
pubsub_channels:0
pubsub_patterns:0
vm_enabled:0
role:slave
master_host:#.#.#.#
master_port:6379
master_link_status:down
master_last_io_seconds_ago:-1
db0:keys=5479113,expires=0
db1:keys=3,expires=0
db3:keys=2,expires=0
db4:keys=1,expires=0
然后查看redis master上面的日志信息：
[457] 25 Mar 11:35:59 - Accepted #.#.#.#:38193
[457] 25 Mar 11:35:59 * Slave ask for synchronization
[457] 25 Mar 11:35:59 * Starting BGSAVE for SYNC
[457] 25 Mar 11:35:59 # Can\'t save in background: fork: Cannot allocate memory
[457] 25 Mar 11:35:59 * Replication failed, can\'t BGSAVE
[457] 25 Mar 11:35:59 - Client closed connection
再查看redis master使用内存的情况，使用3.3G内存
redis> info
redis_version:2.0.4
redis_git_sha1:00000000
redis_git_dirty:0
arch_bits:64
multiplexing_api:epoll
process_id:457
uptime_in_seconds:261600
uptime_in_days:3
connected_clients:2
connected_slaves:0
blocked_clients:0
used_memory:3539375688
used_memory_human:3.30G
changes_since_last_save:19470395
bgsave_in_progress:0
last_save_time:1300764509
bgrewriteaof_in_progress:0
total_connections_received:7130
total_commands_processed:22435670
expired_keys:0
hash_max_zipmap_entries:64
hash_max_zipmap_value:512
pubsub_channels:0
pubsub_patterns:0
vm_enabled:0
role:master
再看一下OS：原来是内存用光了
$free -m
total used free shared buffers cached
Mem: 3951 3900 50 0 0 8
在有内存的情况下，每秒可以达到5w次tps get key[10bytes] value[10bytes]，但19148251万object*(10bytes key length+10bytes value length)/1024/1024=365M,而redis-master用了3.3G的内存，管理结构成本相当大。