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 22:24:19 -0700 (PDT)

:I understand Matt, but over here the problem is the cost of the SSD.
:The Server as a whole costs only $350 so it is not possible to get an
:SSD of $100 sanctioned :-(
:So I guess rsyncing / from one Disk to another will work ( given that
:/usr, /var, /home and Data are mirrored )  ? how do I update the boot
:code on the secong disk? Also since I am following dfly development I
:guess if I dont use mirror-stream I can have a backup of the old
:system in the second disk just in case I get a surprise during
:system/pkgsrc update?
:Thanks :-)

    Yah, rsync works fine, you don't have to use mirror-stream unless you
    need the backup to be near real-time.  And you can use rsync on the
    UFS /boot too.  One advantage of using rsync and NOT mirror-stream
    is that both drives can be mounted R+W.

    With regards to the boot0/boot1/boot2 code, you just install that
    normally on the second disk.  You don't have to worry about updating
    it since it essentially doesn't change.

    You also have choices on the snapshot configuration for the HAMMER
    PFSs.  The default is 60 days worth of daily snapshots but there's
    no reason why the second drive couldn't be configured differently.
    The second drive could be configured for, e.g. 365 days worth of
    snapshots if it is large enough.

    You do have to take into account drive capacity when messing with
    the snapshot configuration.  It's usually best to limit the production
    drive to 60 days just so access remains efficient but the backup
    drive's HAMMER config could be tuned to use considerably more.  I
    wouldn't fill the drive to the brim with snapshots but using like
    75% of the space (and keeping track of it) is fairly easy to maintain.

					Matthew Dillon 

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