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From: Gionatan Danti <g.danti@assyoma.it>
To: LVM general discussion and development <linux-lvm@redhat.com>
Cc: Sreyan Chakravarty <sreyan32@gmail.com>
Subject: Re: [linux-lvm] What is the use of thin snapshots if the external origin cannot be set to writable ?
Date: Mon, 23 Nov 2020 13:44:03 +0100	[thread overview]
Message-ID: <6ea77fe7d910218bb46367f35d1a19a6@assyoma.it> (raw)
In-Reply-To: <CAMaziXsY6vpQdD+QQzW_1Km+Ltf41tz0G1WG5xAUiMARFWHoyw@mail.gmail.com>

Il 2020-11-21 04:10 Sreyan Chakravarty ha scritto:
> I mean what is the point of creating a snapshot if I can't change my
> original volume ?
> 
> Is there some sort of resolution ?

External thin snapshot are useful to share a common, read-only base (ie: 
a "gold-master" image) with different writable thin lvm overlay volumes. 
They can not be merged into external origin; otherwise, a single merge 
operation would invalidate *all* other thin snapshot relying on the same 
origin.

Classical LVM snapshots are good for temporary, short-lived snapshots - 
basically taken for backup purpose only (and immediately removed after 
the backup completed). You should not use them for long-lived snapshots 
(otherwise you can see much lower performance and delayed boot).

If you want to have long-lived snapshot you should use LVM thin 
snapshots. For root volumes, you have two choices:
- use a thin lvm volume for root, which is a supported use case (but it 
will probably require a system reinstallation);
- continue using your classical LVM as a immutable base and use a thin 
lvm with external snapshot to store all new writes.

Regards.


-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8

  reply	other threads:[~2020-11-23 12:47 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-21  3:10 Sreyan Chakravarty
2020-11-23 12:44 ` Gionatan Danti [this message]
2020-11-23 13:04 ` Bryn M. Reeves
2020-11-24 11:59   ` Sreyan Chakravarty
2020-11-25  8:46     ` Sreyan Chakravarty
2020-11-25 12:38     ` Bryn M. Reeves
2020-11-25 15:31       ` Sreyan Chakravarty

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