From: Demi Marie Obenour <demi@invisiblethingslab.com>
To: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Cc: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] Running thin_trim before activating a thin pool
Date: Sun, 30 Jan 2022 13:01:31 -0500 [thread overview]
Message-ID: <YfbSkfdz2cAV4Iaz@itl-email> (raw)
In-Reply-To: <57a77ded-703d-d8a6-a919-2a68ba4cf97f@gmail.com>
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On Sun, Jan 30, 2022 at 06:56:43PM +0100, Zdenek Kabelac wrote:
> Dne 30. 01. 22 v 18:30 Demi Marie Obenour napsal(a):
> > On Sun, Jan 30, 2022 at 12:18:32PM +0100, Zdenek Kabelac wrote:
> > > Discard of thins itself is AFAIC pretty fast - unless you have massively
> > > sized thin devices with many GiB of metadata - obviously you cannot process
> > > this amount of metadata in nanoseconds (and there are prepared kernel
> > > patches to make it even faster)
> >
> > Would you be willing and able to share those patches?
>
> Then are always landing in upstream kernel once they are all validated &
> tested (recent kernel already has many speed enhancements).
Thanks! Which mailing list should I be watching?
> > > What is the problem is the speed of discard of physical devices.
> > > You could actually try to feel difference with:
> > > lvchange --discards passdown|nopassdown thinpool
> >
> > In Qubes OS I believe we do need the discards to be passed down
> > eventually, but I doubt it needs to be synchronous. Being able to run
> > the equivalent of `fstrim -av` periodically would be amazing. I’m
> > CC’ing Marek Marczykowski-Górecki (Qubes OS project lead) in case he
> > has something to say.
>
> You could easily run in parallel individual blkdiscards for your thin LVs....
> For most modern drives thought it's somewhat waste of time...
>
> Those trimming tools should be used when they are solving some real
> problems, running them just for fun is just energy & performance waste....
My understanding (which could be wrong) is that periodic trim is
necessary for SSDs.
> > > Also it's very important to keep metadata on fast storage device (SSD/NVMe)!
> > > Keeping metadata on same hdd spindle as data is always going to feel slow
> > > (in fact it's quite pointless to talk about performance and use hdd...)
> >
> > That explains why I had such a horrible experience with my initial
> > (split between NVMe and HDD) install. I would not be surprised if some
> > or all of the metadata volume wound up on the spinning disk.
>
> With lvm2 user can always 'pvmove' any LV to any desired PV.
> There is not yet any 'smart' logic to do it automatically.
Good point. I was probably unware of that at the time.
--
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab
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next prev parent reply other threads:[~2022-01-30 18:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-29 18:52 [linux-lvm] Running thin_trim before activating a thin pool Demi Marie Obenour
2022-01-29 19:42 ` Zdenek Kabelac
2022-01-29 20:09 ` Demi Marie Obenour
2022-01-29 21:40 ` Zdenek Kabelac
2022-01-30 1:20 ` Demi Marie Obenour
2022-01-30 11:18 ` Zdenek Kabelac
2022-01-30 17:30 ` Demi Marie Obenour
2022-01-30 17:56 ` Zdenek Kabelac
2022-01-30 18:01 ` Demi Marie Obenour [this message]
2022-01-30 18:42 ` Zdenek Kabelac
2022-01-30 20:22 ` Gionatan Danti
-- strict thread matches above, loose matches on Subject: below --
2022-01-29 17:45 Demi Marie Obenour
2022-01-31 11:02 ` Gionatan Danti
2022-01-31 13:41 ` Zdenek Kabelac
2022-01-31 14:12 ` Gionatan Danti
2022-01-31 15:28 ` Demi Marie Obenour
2022-01-31 17:54 ` Gionatan Danti
2022-01-31 19:04 ` Demi Marie Obenour
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