Date: Sun, 30 Aug 2015 06:58:42 -0600 (MDT) From: Warren Block <wblock@wonkity.com> To: Polytropon <freebsd@edvax.de> Cc: freebsd-questions@freebsd.org Subject: Re: Replacing Drive with SSD Message-ID: <alpine.BSF.2.20.1508300633160.44682@wonkity.com> In-Reply-To: <20150829220311.c7608be1.freebsd@edvax.de> References: <CEAD84AD-341A-4FB9-A3A1-D0D5A550AFFD@lafn.org> <alpine.BSF.2.20.1508281235390.74312@wonkity.com> <20150829220311.c7608be1.freebsd@edvax.de>
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On Sat, 29 Aug 2015, Polytropon wrote: > On Fri, 28 Aug 2015 12:47:30 -0600 (MDT), Warren Block wrote: >> If you are a belt-and-suspenders type, create a smallish, maybe 4G, >> partition on the drive that will never be used and leave it empty. >> Don't write to it, ever. This is called over-provisioning. The drive >> sees that all those blocks are free and it can swap them around for wear >> leveling. This can be used in addition to trim. > > To extend the idea (because sometimes I am the axe-and-byrnie type): > Does this also work with _no_ partitions at all? For example, when > the device is formatted "as a whole" (dedicated), like > > # bsdlabel -w ada0 > # bsdlabel -e ada0 > set type "4.2BSD" for 'a' partition > make 'a' same size as 'c' > save > # newfs -m 0 -i 16384 -b 16384 -f 2048 -U -t enable -n disable -L ssdroot /dev/ada0a > # bsdlabel -B ada0 > > where /dev/ada0a has been prepared with bsdlabel to span the entire > device (as in the example) - or in this case, to be a little bit > less (4G) than the whole disk capacity? Making a partition for free space is one way. Another way is to leave part of the drive unpartitioned. Either one just guarantees there is a good supply of unused blocks available to the drive. I'm fairly sure that UFS does not write to every block under its control even during a format. Until written as part of a file, those blocks are also known to be unused. So forcing extra unused space is probably unnecessary most of the time.
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