On Tuesday, November 22, 2011 08:42:10 PM Greg Freemyer wrote:

On Tue, Nov 22, 2011 at 7:44 PM, Joachim Schrod wrote:

...

If you can afford it, don't use 15% of the disk. To get this free space, use secure erase to reset the disk's firmware notion of what you're using, and then don't allocate 15% of the disk during partitioning.

Undocumented feature time. First secure erase is not always implemented on SSDs, so don't trust it.

Second, modern versions of the mkfs tools take care of discard/trim for you. ie. They discard/trim all the unallocated parts of the drive during the format process.

In fact if you don't want that to happen, you have to specify it via:

mkfs.ext4 -E nodiscard /dev/sdxx

I don't know when that was introduced, but os 12.1 has it in the binary, but not in the man page. I strongly suspect 11.4 is similar. No idea about 11.3.

Anyway, XFS uses -K for the same thing. (And its in the man page!)

mkfs.xfs -K /dev/sdxx

So if you really want to keep back 15%, I would create a fullsize partition, format with mkfs, then delete the partition and create one 15% smaller, then format again with mkfs.

Greg What would be a good filesystem catering to SSD strenghts and weaknesses? A friend of mine swears by XFS. -- Roger Luedecke openSUSE Ambassador Ind. Repairs and Consulting **Looking for a C++ etc. mentor*** -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

On Tue, Nov 22, 2011 at 9:44 PM, Adam Tauno Williams wrote:

On Tue, 2011-11-22 at 17:54 -0800, Roger Luedecke wrote:

...

What would be a good filesystem catering to SSD strenghts and weaknesses? A friend of mine swears by XFS

XFS certainly had it's day.  But today I'd use BTRFS.  It has features XFS hasn't even thought about, is rapidly becoming the 'default' filesystem, and ....drumroll... has automatic SSD mode [bulk trim added in 2.6.39 - May 2011].  Mount with the "ssd" option although btrfs will likely set this automatically.

XFS is still very actively maintained. It often gets features like SSD support before any of the other filesystems. ext3 is basically in maintenance only mode. ext4 is actively support, but not yet as mature / stable / feature rich as XFS. Google uses ext4 heavily, but in a configuration that is pretty unique, so much of there dev work is not meaningful for traditional users. (ie. They run without a journal I think. I suspect other application specific tuning also goes on.) btrfs - Is just coming out of experimental status. With the 3.0 kernel it still failed some of the traditional xfstests tests. (That test suite now handles lots of Linux filesystems.) os 12.1 uses the 3.1 kernel. I believe it fixes some of the last of the xfstests identified issues. It may be ready to try for real at this point. Greg -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org

On Wed, Nov 23, 2011 at 5:02 AM, Graham Anderson wrote:

On Tuesday 22 Nov 2011 20:42:10 Greg Freemyer wrote:

...

So if you really want to keep back 15%, I would create a fullsize partition, format with mkfs, then delete the partition and create one 15% smaller, then format again with mkfs.

I thought the idea behind not using all the available space was to give the SSD firmware some additional room for wear/write leveling? What's the benefit of doing as you suggest and creating/formatting a fullsize partion before resizing?

I was clarifying another post which assumed the drive had active data on it. (ie. It wasn't a new SSD). The first post proposed doing a secure erase (via hdparm I assume) to inform the SSD that there was no valid data and it could effectively trim/discard everything. I said secure erase has been known to be buggy on some SSDs, so I would use mkfs to trim/discard the full drive as step one. Then create the partition at whatever size you really want. Greg -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org