freebsd-swap on ssd

[Ivan Voras]

On 17/02/2012 15:16, 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.

This is outdated information as all current SSD drives will perform
internal write-leveling (data relocation) in attempt to get around this.
UFS also has one other benefit: it currently supports the "TRIM"
operation (via BIO_DELETE) while ZFS doesn't.

> 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?

This all depends on how much swap and how often do you use it. I'd say
it's a great idea if you run into out-of-memory situations rarely and
then if you do run into it, you want the least performance degradation.

In *all other cases* you will probably fry the SSD quickly.

> another question i'd like to ask: are there also issues with read-cycles on
> ssds?

Not that I've heard of.

> 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. 

It shouldn't - if the file system is mounted read-only then the
underlying device will not be updated.


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