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From: Gionatan Danti <g.danti@assyoma.it>
To: Zdenek Kabelac <zdenek.kabelac@gmail.com>
Cc: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] lvm-vdo, snapshots and cache
Date: Tue, 15 Nov 2022 23:41:44 +0100	[thread overview]
Message-ID: <df0c4d08b1973c2b506323003f201796@assyoma.it> (raw)
In-Reply-To: <0c1d5e76-085c-cb46-c477-3bcd70a8acb2@gmail.com>

Il 2022-11-15 22:56 Zdenek Kabelac ha scritto:
> You could try  'vg' on top of another 'vg' - however I'd not recommend
> to use it this way (and it's unssuported (&unsupportable) by lvm2 in
> general)

Hi Zdenek,
yeah, I would strongly avoid that outside lab testing.

> IMHO I'd not recommend to combine 2 provisioning technologies - it's
> already hard to resolve 'out-of-space' troubles with just one
> technology...

The issue is that fast snapshots are only provided by dm-thin, meaning 
that lvmthin is almost mandatory for implementing a rolling/continuous 
snapshot scheme. And, on a more basic level, if we can not stack LVM on 
top of a VDO LV (in a supported manner), how can we take a snapshot of 
user data residing on that specific volume?

This seems a clear regression vs a separate VDO device. Am I missing 
something?

> Caching should be already support - on VDO LV as well as on VDOPOOL LV
> (both work somewhat differently).

Good, thanks for confirming. I will do some tests...
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

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  reply	other threads:[~2022-11-15 22:41 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-15 17:42 [linux-lvm] lvm-vdo, snapshots and cache Gionatan Danti
2022-11-15 21:56 ` Zdenek Kabelac
2022-11-15 22:41   ` Gionatan Danti [this message]
2022-11-16 10:50     ` Zdenek Kabelac
2022-11-16 14:38       ` Gionatan Danti
2022-11-16 15:35         ` Zdenek Kabelac

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