From: Sreyan Chakravarty <sreyan32@gmail.com>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] Unusually long boot times with LVM Snapshots
Date: Fri, 20 Nov 2020 21:48:10 +0530 [thread overview]
Message-ID: <CAMaziXss8HAjSjV6g5kFjzkxnYCGZSowfZcT-nJVRm-tf0rJEQ@mail.gmail.com> (raw)
In-Reply-To: <20201120111433.GI1787072@localhost.localdomain>
[-- Attachment #1: Type: text/plain, Size: 2767 bytes --]
On Fri, Nov 20, 2020 at 4:45 PM Bryn M. Reeves <bmr@redhat.com> wrote:
> What type of snapshot are you using? LVM2 allows either "classic" CoW
> snaps,
> or the newer thin provisioned snapshots using the dm-thinp target.
>
> Classic snapshots are known to have very poor IO performance when multiple
> snapshots of the same volume exist simultaneously (especially for write-
> heavy workloads).
>
> Thin provisioned snapshots are not normally activated at boot time unless
> they are explicitly requested (via dracut's rd.lvm.lv options) since they
> have the skip activation flag set by default.
>
>
How can I check which type of snapshot I am using ?
I am very interested in knowing more about these newer snapshots.
I think I am using the older COW snapshots.
I created it using:
sudo lvcreate -L 70GB -s -n test_snapshot
/dev/mapper/vgfedora-fedora
Is there any indication in the log of what's happening during the delay?
> Look through the journalctl output to see if there are any messages logged
> while the delay happens.
>
>
Yes, I have found the reason for the 3 minute delay:
Nov 20 21:14:15 dracut-initqueue[902]: Scanning devices dm-0 for LVM
logical volumes vgfedora/fedora
Nov 20 21:14:16 dracut-initqueue[927]: inactive Original
'/dev/vgfedora/fedora' [700.00 GiB] inherit
Nov 20 21:14:16 dracut-initqueue[927]: inactive Snapshot
'/dev/vgfedora/pre_kde_Nov_9' [70.00 GiB] inherit
Nov 20 21:17:27 systemd[1]: Found device /dev/mapper/vgfedora-fedora.
Nov 20 21:17:27 systemd[1]: Found device
/dev/disk/by-uuid/03aef3ba-dca1-4cba-a3f5-36c5c0fe948e.
Nov 20 21:17:27 systemd[1]: Reached target Initrd Root Device.
As you can see it initializing the snapshots.
This is my entire boot log if you need to delve deeper.
https://pastebin.com/raw/275JPvZB
> Another option is to use systemd-analyze to look into where the time is
> going during boot. It has various commands including "plot" which will
> generate an SVG plot of the boot timings on stdout. You can then compare
> that with a regular boot to try to understand the difference.
>
Well I don't know about "plot" but this is the output from "systemd-analyze
blame"
3min 30.737s dracut-initqueue.service
31.399s udisks2.service
26.650s lvm2-monitor.service
25.500s systemd-journal-flush.service
20.289s ModemManager.service
18.242s abrtd.service
18.233s avahi-daemon.service
18.227s bluetooth.service
17.725s systemd-cryptsetup@luks\x2d2ec7f1ae\x2d6f9b\x2d4896\x2da7b2\x2dbe7809e9d2f4.service
17.604s firewalld.service
As you can see the 3min delay matches with the above LVM entry from the
boot log.
Again, I am very interested in knowing more about these newer snapshots.
--
Regards,
Sreyan Chakravarty
[-- Attachment #2: Type: text/html, Size: 5016 bytes --]
next prev parent reply other threads:[~2020-11-20 16:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 14:16 [linux-lvm] Unusually long boot times with LVM Snapshots Sreyan Chakravarty
2020-11-20 11:14 ` Bryn M. Reeves
2020-11-20 16:18 ` Sreyan Chakravarty [this message]
2020-11-23 13:13 ` Bryn M. Reeves
2020-11-24 11:57 ` Sreyan Chakravarty
2020-11-25 8:45 ` Sreyan Chakravarty
2020-11-25 12:36 ` Bryn M. Reeves
2020-11-25 15:32 ` Sreyan Chakravarty
2020-11-21 8:21 ` Sreyan Chakravarty
2020-11-23 12:52 ` Bryn M. Reeves
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=CAMaziXss8HAjSjV6g5kFjzkxnYCGZSowfZcT-nJVRm-tf0rJEQ@mail.gmail.com \
--to=sreyan32@gmail.com \
--cc=linux-lvm@redhat.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).