Karl Pielorz wrote:
[...]
WARNING: /ssd_db: TRIM flag on fs but disk does not confirm that it
supports TRIM
The filesystem is classic UFS2.
Is TRIM supported throught gmirror, or not?
I think 8.4 is way too old for this. I have a number of 9.2 boxes - and
even on those, TRIM doesn't propagate through gmirror *yet* (at the
time, which is a few months ago I seem to remember reading 'It should
work soon' - but 9.2 doesn't appear to).
You can use gstat to show if any calls to BIO_DELETE are being made - i.e.
gstat -d
On the systems here the 'd/s' (which afaik is 'BIO_DELETE/second')
remains stubbornly at zero :(
Thank you for pointing me to gstat -d. d/s is really zero all the time.
The flipside is with decent SSD's these days TRIM isn't quite so
important... Some may even argue that *not* issuing heaps of BIO_DELETE
on the I/O channel is actually faster - so long as the SSD has time to
play catchup and isn't pegged all the time, I think they may be right :-)
The SSDs in question are holding /var/db/mysql with heavily used InnoDB
tables (grow only ibdata file, few deletes of MyISAM tables) so maybe
there are not much delete commands at all.
Thank you.
Miroslav Lachman
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