SSD support in Anaconda/F14

[Jeff Garzik]

On 12/26/2010 01:53 PM, nodata wrote:
> On 26/12/10 18:42, drago01 wrote:
>> On Sun, Dec 26, 2010 at 6:34 PM, Ray Strode<halfline at gmail.com>   wrote:
>>> Hi,
>>>
>>> On Sun, Dec 26, 2010 at 10:32 AM, drago01<drago01 at gmail.com>   wrote:
>>>> You don't want to use LVM (and you should mount the fs with the
>>>> discard option for trim to work).
>>> At plumbers it came out during the filesystem talk that the discard
>>> option is a really bad idea.  It apparently has performance and
>>> reliabilty problems.  Apparently, you're just supposed to run a
>>> command manually (that I don't remember of hand) when your disk starts
>>> to fill up.
>>
>> Yeah this depends on the drive though (on my Samsung drive it does not
>> seem to have a noticeable performance hit).
>>
>> The tool that can be run from time to time is the "wiper.sh" script
>> found in the hdparm tarball.
>
> Manually running a script "from time to time"? Can't we run this
> automatically instead? Why doesn't the drive do this?

The drive must first be informed of what sectors are empty or occupied, 
because from the TRADITIONAL hard drive's perspective, all sectors are 
always occupied by data.  TRIM/DISCARD command has changed this, by 
creating a method of telling the hard drive what sectors are empty.

Only the filesystem knows which sectors are empty or occupied, so your 
choice is

(a) inform drive of empty sectors, each time a file is deleted

(b) periodically (once a day or week or month, etc.), inform drive of 
empty sectors that have appeared since last check.

Option (a) apparently slows down file deletion noticeably, and 
potentially "erases" sectors that will be immediately re-filled with 
useful data (== extra, unnecessary work).

That leaves option (b).

	Jeff