Date: Mon, 06 Jan 2014 23:07:17 +0100 From: Miroslav Lachman <000.fbsd@quip.cz> To: Karl Pielorz <kpielorz_lst@tdx.co.uk> Cc: freebsd-geom@FreeBSD.org Subject: Re: Is TRIM working with gmirror? Message-ID: <52CB2915.7060602@quip.cz> In-Reply-To: <18C59233568D3A475FF0D843@study64.tdx.co.uk> References: <52A90049.7050001@quip.cz> <18C59233568D3A475FF0D843@study64.tdx.co.uk>
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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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