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From: Zdenek Kabelac <zkabelac@redhat.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	Gionatan Danti <g.danti@assyoma.it>
Subject: Re: [linux-lvm] bcache as a new i/o layer?
Date: Fri, 30 Nov 2018 10:52:34 +0100	[thread overview]
Message-ID: <4dcb6809-f993-4ab1-ab23-0f424e765cd3@redhat.com> (raw)
In-Reply-To: <d2703951-8ad3-9419-82b3-ead1481c58c1@assyoma.it>

Dne 30. 11. 18 v 10:35 Gionatan Danti napsal(a):
> Hi list,
> in BZ 1643651 I read:
> 
> "In 7.6 (and 8.0), lvm began using a new i/o layer (bcache)
> to read and write data blocks."
> 
> Last time I checked, bcache was a completely different caching layer, 
> unrelated from LVM. The above quote, instead, implies that bcache is now 
> actively used by LVM.
> 
> Am I missing something? Can you explain how they interact/behave?



Hi


The name of i/o layer bcache is only internal to lvm2 code for caching
reads form disks during disk processing - the name comes from usage
of  bTree and caching - thus the name bcache.

It's not a dm target - so nothing you could use for LVs.
And has nothing in common with exiting  bcache kernel block device.

The only purpose is to slightly accelerate device scanning and probing - and 
helps mostly in cases your system has tons a devices that needs to be scanned,
since this bcache is also using async disk reads for its filling....


Regards

Zdenek

  reply	other threads:[~2018-11-30  9:52 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-30  9:35 [linux-lvm] bcache as a new i/o layer? Gionatan Danti
2018-11-30  9:52 ` Zdenek Kabelac [this message]
2018-11-30 10:03   ` Gionatan Danti
2018-11-30 10:23     ` Zdenek Kabelac

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