Re: Good SAS adapters for 6 Gb/s SATA SSD's (with TRIM)?

Lukas Czerner
2011-08-12T11:15:14Z

On Fri, 12 Aug 2011, Ric Wheeler wrote:

> On 08/12/2011 10:24 AM, Prof. Dr. Klaus Kusche wrote:
> > On 2011-08-12 11:01, Ric Wheeler wrote:
> > > Lukas has a more generic bulk tool that should do the job and has the
> > > advantage that it does not have to fill the file system first (it can
> > > lock regions and do its work).
> >
> > Any pointers to that?
>
> I think that the easiest (and most natural way) to do this is through the
> updated fsck (-K) tool which will discard the unused block ranges when you
> fsck a file system.
>
> Lukas can add in details about versions, etc :)

Yes, you can use e2fsck to discard unused parst of the file system,
hence reclaiming the space. This feature has been added with
v1.41.12-162-gefa1a35 into e2fsprogs. Note that even though this
operation should be safe, because we do discard at the end of the pass 5
and only if there was not any errors on the file system before, however
this is relatively new feature and has not been extensively tested with
corrupted images.

Hmm, I really should write up this stuff into the web article somewhere
:).

Thanks!
-Lukas

>
> >
> > Thanks!
> >
> > > Note that discard is not just for physical devices like SCSI or ATA, it
> > > is also useful for "software" stacks like various device mapper targets,
> > > virtual block devices, etc so we should be keeping the abstraction at a
> > > high level for our tooling.
> >
> > I agree, but wiper.sh has been the first such tool and is widespread
> > and well-known. I'm not aware of alternatives using the generic fstrim
> > command (which is still missing on some major distributions)
> > or FITRIM ioctl.
> >
>
> FITRIM is somewhat misnamed. It will end up issuing a discard to the storage
> stack, not an ATA specific TRIM command (invoking sb_issue_discard()).
>
> Anything that uses FITRIM should work if I followed the code correctly,
>
> Ric
>
>
>
>