Re: Parameters for PostgreSQL

Craig Ringer <craig@xxxxxxxxxxxxxxxxxxxxx> · Thu, 04 Aug 2011 11:54:48 +0800



    On 04/08/11 11:42, Jayadevan M wrote:
    
      
       Hello, 
      

        >The most important spec has been omitted. What's the storage
        subsystem? 
      

       We have storage on SAN, RAID 5.

    
    RAID 5? That's *really* not ideal for database workloads, either Pg
    or Oracle, unless your RAID 5 storage backend has enough
    battery-backed write cache to keep huge amounts of writes in RAM and
    reorder them really effectively.

    
    I hope each RAID 5 LUN is only across a few disks and is layered
    with RAID 1, though. RAID 5 becomes less reliable than using a
    single disk when used with too many HDDs, because the probability of
    a double-disk failure becomes greater than that of a single
    standalone disk failing. After being bitten by that a few times,
    these days I'm using RAID 6 in most cases where RAID 10 isn't
    practical.

    
    In any case, "SAN" can be anything from a Linux box running an iSCSI
    target on top of a RAID 5 `md' software RAID volume on four 5400RPM
    HDDs, right up to a giant hundreds-of-fast-disks monster filer full
    of dedicated ASICs and great gobs of battery backed write cache
    DRAM. Are you able to be any more specific about what you're dealing
    with?

    
        > > We are suing weblogic.

        >           ^^^^^

        > Best. Typo. Ever.

        > 

        > I hear most people who use it want to, you're just brave
        enough to
        do it :-P

        I wish I could make a few millions that way. 
      

       Thank you for all the replies. The first step is,
        of course, to migrate the data. I am working with ora2pg for
        that. I assume
        creating files with 'COPY' to work as input for PostgreSQL is
        the right
        approach? We don't have many stored procedures or packages. So
        that part
        should be OK.