enable TRIM by default ?

[Warner Losh]

> On Dec 3, 2014, at 12:14 AM, Peter Jeremy <peter at rulingia.com> wrote:
> 
> On 2014-Dec-02 07:43:13 +0000, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
>> Isn't it time that we enable TRIM by default in newfs ?
> 
> As an alternative viewpoint, I have a SSD that got severe indigestion when
> I tried to enable TRIM:
> aspire kernel: ad0: TIMEOUT - CFA ERASE retrying (1 retry left)
> aspire kernel: ad0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
> aspire kernel: ata1: error issuing SETFEATURES ENABLE WCACHE command
> aspire kernel: ata1: error issuing SET_MULTI command
> aspire kernel: ata1: error issuing WRITE_DMA command
> The kernel then went to 1 core of interrupt and wedged.

Is this a SSD, or a CF card of some flavor. The CFA ERASE trim method
pre-dates the much better and easier to use DSM (Data Set Trim) method
that more modern SSDs use. Perhaps we can take a cue off of that? Or
maybe the detection for when to use CFA ERASE is busted since it was
only ever supposed to be used with CF cards...

> I admit that it's about 3 years old but smartctl says it's still got lots of
> life left in it and googling suggests they are still available.
> 
> The problem is that if a SSD doesn't support TRIM, it is likely to have all
> sorts of misbehaviour if you attempt to enable TRIM.  If TRIM is enabled by
> default, you need to provide a simple way to disable it if the system can't
> cope.

Except that’s not what’s being proposed. Enabling TRIM by default means
turning trim on in newfs which will not turn on for drives that don’t set the
CANDELETE flag. IF the drive doesn’t advertise support for either CFA ERASE
or DSM TRIM (in the ata world), nothing changes.

Three year old flash is outside its warrantee period, even if smartctl suggests
there’s still life in it.

Warner


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