Unable to read and write data about fatcache HOT 8 CLOSED

@mimingan

good catch about missing fc_client.h and fc_server.h files. I uploaded a new distribution with a fix for missing files. See: https://code.google.com/p/fatcache/downloads/list

Regarding writing to ssd, it seems like your fatcache instance is working as expected. If you read through the README.md, you will notice that fatcache first writes to memory and then batch writes slabs to ssd. I don't see any error in the log file that you uploaded

Could you describe the issue you are encountering in detail?

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@manjuraj

Thank you for your reply to us so quickly. Sorry, I do not describe the problem in detail.

Accordance with the above method, I run the fatcache.

The "set" and "get" commands execution is a failure.

For example:

printf "set zhangyan 0 0 5\r\n12345\r\n" | nc 127.0.0.1 11211

printf "set zhang07 0 0 6\r\n123456\r\n" | nc 127.0.0.1 11211

printf "set zhang900 0 0 3\r\n456\r\n" | nc 192.168.1.3 11211

printf "get zhang07\r\n" | nc 127.0.0.1 11211

And so on. Repeatedly executed several times, the above commands are a failure .

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@manjuraj

Thank you for your reply.

I downloaded the fatcache-0.1.1.tar.gz.

Now, the "set" and "get" commands execution is OK, thanks.

testing...

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@manjuraj

I use the 'set' command of libmemcached, write a data to fatcache, spending 600 - 1000 ms.(very slowly)
use mcperf the same as libmemcached.
I didn't know why. can you tell me, thanks.
have I wrong usage ？

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Is the backing store a ssd or disk?
You can also look at the perf results in notes/ folder to get an idea on how to use fatcache

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In practical work, we feel the fatcache very low performance . testing is as follows,
//code
uint32_t flags = 0;
time_t dur_time = 0;
struct timeval start = {0}, end = {0};
gettimeofday(&start, NULL);
rc = memcached_set(memc_, key.c_str(), key.length(), value.c_str(), value.length(), dur_time, flags);
gettimeofday(&end, NULL);
printf("cache 'set' cmd time: %ld ms.", diff_time(&start, &end) / 1000);

1. connect to a fatcache (127.0.0.1:11211)
   Start the fatcache.
   /usr/local/fatcache/bin/fatcache -d -o /usr/local/fatcache/log/fatcache.log -D /dev/sdb

log:
Wed Aug 14 09:34:00 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 1000 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 1000 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 1000 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 1000 ms.
Wed Aug 14 09:34:01 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 0 ms.
Wed Aug 14 09:34:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.
Wed Aug 14 09:34:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 999 ms.

1. connect to a memcached (192.168.1.3:11211)
   log:
   Wed Aug 14 11:04:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 0 ms.
   Wed Aug 14 11:04:02 2013 [common/memcached/mycache.cpp]:[93]:[set_key_value] cache 'set' cmd time: 0 ms.
2. Large concurrent case
   /usr/local/mcperf/bin/mcperf --sizes=u100,100 --num-calls=10000 --num-conns=100 --call-rate=1000 --conn-rate=10000 --method=set --server=192.168.1.3 --port=11211
   Total: connections 100 requests 1000000 responses 1000000 test-duration 10.010 s
   Request rate: 99904.8 req/s (0.0 ms/req)
   Request size [B]: avg 129.0 min 129.0 max 129.0 stddev 0.00
   Response rate: 99904.8 rsp/s (0.0 ms/rsp)
3. only execute once 'set' command.
   The fatcache is very slow. spending 1000 ms，
   but the memcached is far less than 1 ms.
4. Have you done once 'set' command to test?
   Thanks for your reply.

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@mimingan

please read this: https://github.com/twitter/fatcache/blob/master/notes/performance.md and this: https://github.com/twitter/fatcache/blob/master/notes/intel-ssd-320-specification.pdf and this: https://github.com/twitter/fatcache/blob/master/notes/spec.md

your backing store must be SSD. On your SSD figure out what its read and write latencies and your latency numbers would be something similar for a 4K read / write.

hth, let me know if you how the testing works out

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closing this for now. feel free to reopen if you have questions

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