redis becomes very slow while bgsave

[Parveen Jain]

Hi,

 We are using redis for one of my application, but getting intermittent(frequency in 5-6 hours ) this kind of save which is takes  from 20-30 minutes to 60 minutes(in Red). For rest of the times it works quite normally and save almost same size of data in 2-3 minutes.

Can anyone please suggest me where should I look into. I am using default redis configuration file with redis 2.8.

[29218] 02 Apr 07:01:46.077 * 10000 changes in 60 seconds. Saving...
[29218] 02 Apr 07:01:46.639 * Background saving started by pid 625
[625] 02 Apr 07:04:35.980 * DB saved on disk
[625] 02 Apr 07:04:36.298 * RDB: 112 MB of memory used by copy-on-write
[29218] 02 Apr 07:04:37.376 * Background saving terminated with success
[29218] 02 Apr 07:05:38.030 * 10000 changes in 60 seconds. Saving...
[29218] 02 Apr 07:05:38.632 * Background saving started by pid 6902
[6902] 02 Apr 07:27:08.419 * DB saved on disk
[6902] 02 Apr 07:27:08.921 * RDB: 775 MB of memory used by copy-on-write
[29218] 02 Apr 07:27:10.128 * Background saving terminated with success
[29218] 02 Apr 07:28:11.276 * 10000 changes in 60 seconds. Saving...
[29218] 02 Apr 07:28:11.853 * Background saving started by pid 11379
[11379] 02 Apr 09:23:48.750 * DB saved on disk
[11379] 02 Apr 09:23:49.284 * RDB: 2180 MB of memory used by copy-on-write
[29218] 02 Apr 09:23:50.907 * Background saving terminated with success
[29218] 02 Apr 09:24:51.232 * 10000 changes in 60 seconds. Saving...
[29218] 02 Apr 09:24:51.885 * Background saving started by pid 1122
[1122] 02 Apr 09:36:02.847 * DB saved on disk
[1122] 02 Apr 09:36:03.209 * RDB: 777 MB of memory used by copy-on-write
[29218] 02 Apr 09:36:04.345 * Background saving terminated with success

Thanks,

Parveen Jain

[Josiah Carlson]

Do you have periodic changes in the load you are executing that could be writing more? Or... are you running in a virtualized environment like AWS and writing your snapshots to EBS? If so, that might be it right there - network IO issues, noisy neighbor, etc.

You might have better luck using AOF. You would get better persistence 99% of the time, with tunable parameters for how often you would rewrite the AOF.

Oh, can you provide the output of "INFO"? And the first 10 or so lines of top? I'm just looking for the memory and CPU information, not a process list.

 - Josiah

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