DragonFly BSD
DragonFly users List (threaded) for 2010-03
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Re: PFS mirroring insted of RAID Improved set up - need comments.

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 29 Mar 2010 08:48:21 -0700 (PDT)

    In terms of booting, if that is a worry then buy a $100 SSD and boot
    from that (as well as put your swap on it and turn on swapcache,
    2 for 1 deal!).  You could even put root on the SSD too and use tmpfs
    for /tmp.  There's no real need to have RAIDed SSDs since their MTBF
    is going to be approximately the same as the motherboard anyway.

    Redundant multi-master HAMMER is a goal but we don't have it yet, and
    we aren't thinking of it for booting in particular.

    Another option is to boot off the network with a NFS root and do the
    more complex local disk mounts from that basis.

    The major system storage could then use a RAIDed system or a mirror
    with failover... ultimately I guess a multi-master HAMMER system when
    we have it.  For now all we really have is vinum and a few RAID card
    vendors.  RAID-5 is kinda on its way out for smaller installations
    because individual hard drives have gotten so large.  These days you
    generally just want to use a RAID 10 configuration.  And for bigger
    installations you buy a commercial RAID enclosure which does
    everything for you and just gives you a SATA connector.

    Generally speaking I'm against trying to boot off of complex storage
    topologies.  It results in a high potential for hitting a complexity
    failure (overengineering a system to the point where it becomes so
    inflexible that you can't fix it when something else breaks).  And, as
    I mentioned, a single $100 SSD solves the problem anyway.  People
    need to remember that the motherboard itself is not redundant so
    frankly if you need a solution for booting you also need a solution
    for a motherboard going bad.


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