Need help analysing the VarnishStat results

Question

I am a newbie with Varnish. I have successfully installed it and now its working, but I need some guidance from the more knowledgeable people about how the server is performing.

I read this article - http://kristianlyng.wordpress.com/2009/12/08/varnishstat-for-dummies/ but I am still not sure howz the server performance.

The server has been running since last 9 hours. I understand that more content will be cached with time so cache hit ratio will better, but right now my concern is about intermediate help from your side on server performance.

Hitrate ratio:       10      100      613
Hitrate avg:     0.2703   0.3429   0.4513

      239479         8.00         7.99 client_conn - Client connections accepted
      541129        13.00        18.06 client_req - Client requests received
      157594         1.00         5.26 cache_hit - Cache hits
           3         0.00         0.00 cache_hitpass - Cache hits for pass
      313499         9.00        10.46 cache_miss - Cache misses
       67377         4.00         2.25 backend_conn - Backend conn. success
      316739         7.00        10.57 backend_reuse - Backend conn. reuses
         910         0.00         0.03 backend_toolate - Backend conn. was closed
      317652         8.00        10.60 backend_recycle - Backend conn. recycles
         584         0.00         0.02 backend_retry - Backend conn. retry
           3         0.00         0.00 fetch_head - Fetch head
      314040         9.00        10.48 fetch_length - Fetch with Length
        4139         0.00         0.14 fetch_chunked - Fetch chunked
           5         0.00         0.00 fetch_close - Fetch wanted close
         386          .            .   n_sess_mem - N struct sess_mem
          55          .            .   n_sess - N struct sess
      313452          .            .   n_object - N struct object
      313479          .            .   n_objectcore - N struct objectcore
       38474          .            .   n_objecthead - N struct objecthead
         368          .            .   n_waitinglist - N struct waitinglist
          12          .            .   n_vbc - N struct vbc
          61          .            .   n_wrk - N worker threads
         344         0.00         0.01 n_wrk_create - N worker threads created
        2935         0.00         0.10 n_wrk_queued - N queued work requests
           1          .            .   n_backend - N backends
          47          .            .   n_expired - N expired objects
      149425          .            .   n_lru_moved - N LRU moved objects
           1         0.00         0.00 losthdr - HTTP header overflows
      461727        10.00        15.41 n_objwrite - Objects sent with write
      239468         8.00         7.99 s_sess - Total Sessions
      541129        13.00        18.06 s_req - Total Requests
       64678         3.00         2.16 s_pipe - Total pipe
        5346         0.00         0.18 s_pass - Total pass
      318187         9.00        10.62 s_fetch - Total fetch
   193589421      3895.84      6459.66 s_hdrbytes - Total header bytes
  4931971067     14137.41    164569.09 s_bodybytes - Total body bytes
      117585         3.00         3.92 sess_closed - Session Closed
        2283         0.00         0.08 sess_pipeline - Session Pipeline
         892         0.00         0.03 sess_readahead - Session Read Ahead
      458468        10.00        15.30 sess_linger - Session Linger
      414010         9.00        13.81 sess_herd - Session herd
    36912073       880.96      1231.68 shm_records - SHM records

Answer 1

What VCL are you using? If the answer is 'none' then you are probably not getting a very good hitrate. On a fresh install, Varnish is quite conservative about what it caches (and rightly so), but you can probably improve matters by reading how to achieve a high hitrate. If it's safe to, you can selectively unset cookies and normalise requests with your VCL, which will result in fewer backend calls.

How much of your website is cacheable? Is your object cache big enough? If you can answer those two questions, you ought to be able to achieve a great hitrate with Varnish.