Re: Performances issues with SSD volume ?

Thomas SIMON <tsimon@xxxxxxxxxxx> · Mon, 18 May 2015 16:21:12 +0200



    Hi Wei,

      Yes i'm using RAID (megacli card), battery is ok, i had already
      checked BBU :)

      
      Cheers

      Thomas
      Le 18/05/2015 15:52, Wei Shan a écrit :

    
      Hi Thomas, 
      This is just a wild guess. Are you using hardware
        RAID? Is the cache battery still working?
      Cheers
      On 18 May 2015 9:36 pm, "Thomas SIMON"
        <tsimon@xxxxxxxxxxx>
        wrote:

        
            Hi matheus,

              thanks for reply.

              
              Kernel is slightly different ; with a
              3.10.23-xxxx-std-ipv6-64 kernel (OVH kernel) on HDD
              server, and  3.2.65-1+deb7u1 kernel on SSD server.

              I'm using debian wheezy on both servers.

              
              I didn't changed the 2 parameters you talk about.

              
              Thanks,
              Thomas
              Le 18/05/2015 15:13, Matheus de Oliveira a écrit :

            
                  On Mon, May 18, 2015 at 10:05
                    AM, Thomas SIMON <tsimon@xxxxxxxxxxx>
                    wrote:

                    
                      After the change, I had the following behavior,
                      and I don't understand why : everything seems to
                      work fine (load is ~6/7, when it was previously
                      ~25/30 on the HDD server), so the SSD server is
                      faster than the HDD one, and my apps run faster
                      too, but after some time (can be 5 minutes or 2
                      hours), the load average increases suddently (can
                      reach 150 !) and does not decrease, so postgres
                      and my application are almost unusable. (even
                      small requests are in statement timeout)
                  
                  
                Before we go mad, what is the
                  OS/kernel/distro that you are using? Did it change
                  from the previous one?

                  
                  If Linux, have you disabled transparent_huge_pages and
                  zone_reclaim_mode (two known problematic Linux
                  features)?

                
                Best regards,

                
                -- 

                  Matheus de Oliveira

                    Analista de Banco de Dados

                    Dextra Sistemas - MPS.Br nível F!

                    www.dextra.com.br/postgres