linux-lvm.redhat.com archive mirror
 help / color / mirror / Atom feed
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>


[-- Attachment #1.1: Type: text/plain, Size: 2369 bytes --]

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

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

[-- Attachment #2: Type: text/plain, Size: 201 bytes --]

_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

  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 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YfbSkfdz2cAV4Iaz@itl-email \
    --to=demi@invisiblethingslab.com \
    --cc=linux-lvm@redhat.com \
    --cc=zdenek.kabelac@gmail.com \
    --subject='Re: [linux-lvm] Running thin_trim before activating a thin pool' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).