Re: How to best use 32 15k.7 300GB drives?

Robert Schnabel <schnabelr@xxxxxxxxxxxx> · Fri, 28 Jan 2011 15:33:28 -0600



    On 1/28/2011 11:44 AM, Scott Carey wrote:
    
      
          On 1/27/11 4:11 PM, "Alan Hodgson" <ahodgson@xxxxxxxxx>
            wrote:
        
        
              On January 27,
                2011, Robert Schnabel <schnabelr@xxxxxxxxxxxx>
                wrote:
              > So my
                questions are 1) am I'm crazy for doing this, 2) would
                you change
              > anything
                and 3) is it acceptable to put the xlog & wal (and
                perhaps tmp
              > filespace)
                on a different controller than everything else? Please
                keep
              > in mind I'm
                a geneticist who happens to know a little bit about
              >
                bioinformatics and not the reverse. :-)
              > 
              Putting the WAL
                on a second controller does help, if you're write-heavy.
              I tried
                separating indexes and data once on one server and
                didn't really notice that it helped much. Managing the
                space was problematic. I would suggest putting those
                together on a single RAID-10 of all the 300GB drives
                (minus a spare). It will probably outperform separate
                arrays most of the time, and be much easier to manage.
            
          
      If you go this route, I suggest two equally sized RAID 10's
        on different controllers fir index + data, with software raid-0
        on top of that.  RAID 10 will max out a controller after 6 to 10
        drives, usually.  Using the OS RAID 0 to aggregate the
        throughput of two controllers works great.
      

      WAL only has to be a little bit faster than your network in
        most cases.  I've never seen it be a bottleneck on large bulk
        loads if it is on its own controller with 120MB/sec write
        throughput.  I suppose a bulk load from COPY might stress it a
        bit more, but CPU ends up the bottleneck in postgres once you
        have I/O hardware this capable.
      

    Do you mean 14 drives in one box as RAID10's on one controller, then
    14 drives in the other box on a second controller, then software
    RAID0 each of the two RAID10's together essentially as a single 4 TB
    array?  Would you still recommend doing this with Windows?

    Bob