Re: Does mdadm supports TRIM command to SSDs?

[Bernd Schubert <bernd.schubert@fastmail.fm>]

On 07/11/2012 01:27 PM, David Brown wrote:
> On 07/11/2012 12:55 AM, Bar Ziony wrote:
>> Hi,
>>
>> I wasn't able to find any information about it after searching for
>> hours - Does mdadm supports sending the TRIM command to SSDs, if using
>> the right filesystem with the 'discard' flag?
>> If it does support it, from what kernel version it is?
>>
>> Thank you,
>> Bar.
> 
> The big question here is /why/ would you want TRIM support?  In many
> circumstances it leads to slower operations, and for SSDs from the past
> couple of years it is almost entirely superseded by the SSD's own
> garbage collection.
> 
> So while there certainly has been some work done on TRIM and md raid, it
> is not a priority as it is of questionable benefit.  You might find some
> operations are a little faster for older SSDs if you use TRIM, but your
> metadata operations will be a lot slower.
> 
> Your best bet is just to make sure you only buy SSDs that are at least
> half decent, and don't worry about TRIM.


Well, we do have not-so-old Intel 510 SSDs on our institute cluster and
these SSDs really need trim. And it gives us quite some headache for
some reason (reason is an annoying LSI SAS controller they are connected
to).


Cheers,
Bernd