Date: Tue, 7 Jan 2014 00:02:46 -0000 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Miroslav Lachman" <000.fbsd@quip.cz>, "Karl Pielorz" <kpielorz_lst@tdx.co.uk> Cc: freebsd-geom@FreeBSD.org Subject: Re: Is TRIM working with gmirror? Message-ID: <7FBCC53840FA45928B9F527EA235B632@multiplay.co.uk> References: <52A90049.7050001@quip.cz> <18C59233568D3A475FF0D843@study64.tdx.co.uk> <52CB2915.7060602@quip.cz>
next in thread | previous in thread | raw e-mail | index | archive | help
----- Original Message -----
From: "Miroslav Lachman" <000.fbsd@quip.cz>
To: "Karl Pielorz" <kpielorz_lst@tdx.co.uk>
Cc: <freebsd-geom@FreeBSD.org>
Sent: Monday, January 06, 2014 10:07 PM
Subject: Re: Is TRIM working with gmirror?
> 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.
Delete's are only support by CAM currently so if your device is
not connected to a CAM based driver e.g. daX or adaX then its
likely not getting through to the device.
Not sure if this has been mentioned but you also need to have
filesystem support, as your talking about gmirror I assume your
using UFS which would need to be TRIM enabled using tunefs -t enable,
see man tunefs for more info.
Regards
steve
================================================
This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it.
In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337
or return the E.mail to postmaster@multiplay.co.uk.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?7FBCC53840FA45928B9F527EA235B632>