Replacing Drive with SSD
wblock at wonkity.com
Sun Aug 30 12:58:55 UTC 2015
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'
> # 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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