Re: multiple journals on SSD

Goncalo Borges <goncalo.borges@xxxxxxxxxxxxx> · Thu, 7 Jul 2016 14:01:05 +1000



    Hi George...
    

    On my latest deployment we have set
    
      # grep journ /etc/ceph/ceph.conf

        osd journal size = 20000
    
    and configured the OSDs for each device running 'ceph-disk
      prepare'

    
      # ceph-disk -v prepare --cluster ceph --cluster-uuid XXX
        --fs-type xfs /dev/sdd /dev/sdb

        # ceph-disk -v prepare --cluster ceph --cluster-uuid XXX
        --fs-type xfs /dev/sde /dev/sdb

        # ceph-disk -v prepare --cluster ceph --cluster-uuid XXX
        --fs-type xfs /dev/sdf /dev/sdb

        # ceph-disk -v prepare --cluster ceph --cluster-uuid XXX
        --fs-type xfs /dev/sdg /dev/sdb

        
    where sdb is an SSD.  Once the previous commands finish, this is
      the partition layout they create for the journal 

    
      # parted -s /dev/sdb p

        Model: DELL PERC H710P (scsi)

        Disk /dev/sdb: 119GB

        Sector size (logical/physical): 512B/512B

        Partition Table: gpt

        Disk Flags: 

        
        Number  Start   End     Size    File system  Name          Flags

         1      1049kB  21.0GB  21.0GB               ceph journal

         2      21.0GB  41.9GB  21.0GB               ceph journal

         3      41.9GB  62.9GB  21.0GB               ceph journal

         4      62.9GB  83.9GB  21.0GB               ceph journal

      
    However, never tested more than 4 journals per ssd.

    
    Cheers

    G.

    
    On 07/06/2016 10:03 PM, George Shuklin
      wrote:

    
    Hello.
      

      I've been testing Intel 3500 as journal store for few HDD-based
      OSD. I stumble on issues with multiple partitions (>4) and UDEV
      (sda5, sda6,etc sometime do not appear after partition creation).
      And I'm thinking that partition is not that useful for OSD
      management, because linux do no allow partition rereading with it
      contains used volumes.
      

      So my question: How you store many journals on SSD? My initial
      thoughts:
      

      1)  filesystem with filebased journals
      

      2) LVM with volumes
      

      Anything else? Best practice?
      

      P.S. I've done benchmarking: 3500 can support up to 16 10k-RPM
      HDD.
      

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    -- 
Goncalo Borges
Research Computing
ARC Centre of Excellence for Particle Physics at the Terascale
School of Physics A28 | University of Sydney, NSW  2006
T: +61 2 93511937
  

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