freebsd-swap on ssd
julian at freebsd.org
Fri Feb 17 18:17:29 UTC 2012
On 2/17/12 6:16 AM, Alexander Best wrote:
> hi there,
> putting a freebsd-ufs partition on an ssd isn't recommended, since the ufs
> structure (unlike zfs e.g.) requires certain data to be continuously written to
> a fixed location and thus will cause the ssd to quickly run out of write-cycles
> and die.
the SSD doesn't use the same flash for the same logical locatio each time!
it maps it to different locations each time.
> but how about using a small ssd (approx. 10GB) as one entire freebsd-swap
> partition? will this make more sense, or are there certain structures within
> the freebsd-swap partition type, which also need to be continuously written to
> a fixed location?
small SSDs may have less wear resistance than big ones.. the cheap
ones may not even
use proper mapping..
> another question i'd like to ask: are there also issues with read-cycles on
> ssds? because i was thinking about putting a freebsd-boot partition on an ssd
> drive and only mounting it ro. this should solve the write-cycle issue in
> theory. however i'm not sure, if stuff like the dirty bit or the ufs label will
> also remain untouched. so even though the partition will only be mounted ro,
> freebsd might still frequently write certain data to a fixed location on the
> ssd drive which hosts the freebsd-boot partition. if this is the case, is there
> a way of completely prohibiting any writes to a disk? will revoking any write
> permissions from the device entry under /dev guarantee this, or is using a any
> device 100% ro under freebsd impossible (unless it has a hardware switch to
> forbid writes)?
yes there are small issues with read cycles but it is all hidden from
you by the drive.
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