Date: Tue, 3 May 2011 15:25:17 +0200 From: Bernd Walter <ticso@cicely7.cicely.de> To: Alexander Leidinger <Alexander@Leidinger.net> Cc: freebsd-fs@freebsd.org, Alexander Motin <mav@freebsd.org>, Pawel Jakub Dawidek <pjd@freebsd.org> Subject: Re: TRIM clustering Message-ID: <20110503132517.GF1549@cicely7.cicely.de> In-Reply-To: <20110503134826.712070yt2urhxp8g@webmail.leidinger.net> References: <4DBBB20A.5050102@FreeBSD.org> <20110430072831.GA65598@icarus.home.lan> <20110501000656.00007ea1@unknown> <20110501133752.GC3245@garage.freebsd.pl> <20110503134826.712070yt2urhxp8g@webmail.leidinger.net>
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On Tue, May 03, 2011 at 01:48:26PM +0200, Alexander Leidinger wrote: > Quoting Pawel Jakub Dawidek <pjd@FreeBSD.org> (from Sun, 1 May 2011 > 15:37:52 +0200): > > >On Sun, May 01, 2011 at 12:06:56AM +0200, Alexander Leidinger wrote: > >>On Sat, 30 Apr 2011 00:28:31 -0700 Jeremy Chadwick > >><freebsd@jdc.parodius.com> wrote: > >> > >>> On Sat, Apr 30, 2011 at 09:54:02AM +0300, Alexander Motin wrote: > >> > >>> Other notes: TRIM needs to be supported on swap as well, and in my > >>> opinion this is just as important as it being in UFS. I'm not sure > >>> how one would implement that. > >> > >>This brings up the question if a ZFS cache (where the contents do not > >>survive a reboot) is completely TRIMmed before used (and normally > >>trimmed during use)... > > > >It is not trimmed at all. > > This does not sound like the optimal solution... is there a way to > know the first access after boot/attach to a cache device? If yes, > would it be possible to TRIM the complete provider (except for some > static data which needs to be there) from this place? This would not > solve the not TRIMmed during use part, put at least a reboot/reattach > could provide a sane state. What would be the possible benefit? I mean it's just until the device is filled, which won't happen that regular in environments where cache devices make sense. More interesting would be to have the cached data reboot persistent one day instead of TRIMing it. -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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