solid-state drives

Matthew Dillon dillon at
Wed Aug 1 19:30:50 PDT 2012

:This is a spinoff of the Aleutia question, since Aleutia puts SSDs in 
:computers. How does the periodic Hammer job handle SSDs? Does reblocking do 
:anything different than on an HDD? If a computer has an SSD and an HDD, which 
:should get the swap space?
:lo ponse be lo mruli po'o cu ga'ezga roda lo ka dinko

    It depends on the purpose.  I run several laptops with both swap and
    root on the SSD.  Obviously swapcache is turned off in that situation.
    I usually adjust the hammer config to turn off the 'recopy' feature
    and I usually set the reblocker to run less often, but that's about

    I only suggest running a hammer filesystem on a SSD under carefully
    controlled conditions... that is, not if you are going to be manipulating
    any large databases that could blow out the SSD.  Normal laptop use
    should work fine but one always has to be cognizant of the SSD's limited
    write cycles.


    For machines that are working harder or which need a lot of disk space
    I run hammer on the HDD and put swap on the SSD, and enable swapcache.
    The SSD works very well as a cache under these circumstances.

    You still need to avoid heavy paging due to running programs which
    are too big to fit into memory, since that can wear out the SSD.

    This is my preferred setup.  All the DragonFly boxes run with SSD-based
    swap and swapcache turned on.

					Matthew Dillon 
					<dillon at>

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