Bob Proulx:
>
> The wiki does say this:
>
> * The "discard" options is not needed if your SSD has enough
> overprovisioning (spare space) or you leave (unpartitioned) free
> space on the SSD.
> See http://www.spinics.net/lists/raid/msg40866.html
AFAIU, this discussion only relates to "online trim" (using the
"discard" mount option). Running an occasional fstrim on your
filesystems is almost free and, apart from RAID issues, I don't see any
negative consequences. Am I missing something?
> The referenced thread has much good information concerning trim (aka
> the discard option) and I recommend reading through the entire thread.
> You are fine with trim enabled. In some cases using trim may help.
> In some cases using trim may hurt. I haven't enabled it on my main
> laptop. I am using a high quality SSD that has a signfican't amount
> of internal over-provisioning.
What's "significant"? I remember seeing graphs on anandtech.com about
drive performance with respect to the amount of unused space on SSDs. I
think the result was that you see significant perfromance gains when you
set aside 10-20% of space *in addition to the manufacturer's spare
area*.
Wait a minute … yes, that's the article I am thinking of:
http://www.anandtech.com/show/6489/playing-with-op
Note the logarithmic scale. Obviously, the results are highly
hardware-dependent, but I don't think things have changed very much
since Q4 2012.
If you use TRIM (either using the discard mount option or using fstrim
regularly), your usable spare area is manufacturer spare area plus free
space on your filesystem. If you don't use TRIM (and don't keep
unpartitioned space), your spare area is only as large as what the
manufacturer intended it to be.
J.
--
If I was a supermodel I would give all my cocaine to the socially
excluded.
[Agree] [Disagree]
<http://www.slowlydownward.com/NODATA/data_enter2.html>
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