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From: Gionatan Danti <g.danti@assyoma.it>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	Zdenek Kabelac <zkabelac@redhat.com>, Ilia Zykov <mail@izyk.ru>
Subject: Re: [linux-lvm] Why doesn't the lvmcache support the discard (trim) command?
Date: Fri, 19 Oct 2018 14:45:02 +0200	[thread overview]
Message-ID: <707aafdc-cfd2-3bdd-13bb-1bfdc08c6ad9@assyoma.it> (raw)
In-Reply-To: <36f0f734-c49f-eaf9-7ff5-8aedfd7345b3@redhat.com>

On 19/10/2018 12:58, Zdenek Kabelac wrote:
> Hi
> 
> Writecache simply doesn't care about caching your reads at all.
> Your RAM with it's page caching mechanism keeps read data as long as 
> there is free RAM for this - the less RAM goes to page cache - less read 
> operations remains cached.

Hi, does it mean that to have *both* fast write cache *and* read cache 
one should use a dm-writeback target + a dm-cache writethrough target 
(possibly pointing to different devices)?

Can you quantify/explain why and how faster is dm-writeback for heavy 
write workload?

Thanks.

-- 
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:[~2018-10-19 12:45 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-18 22:56 [linux-lvm] Why doesn't the lvmcache support the discard (trim) command? Ilia Zykov
2018-10-19  9:12 ` Zdenek Kabelac
2018-10-19  9:42   ` Gionatan Danti
2018-10-19  9:49     ` Zdenek Kabelac
2018-10-19  9:55   ` Ilia Zykov
2018-10-19 10:58     ` Zdenek Kabelac
2018-10-19 12:45       ` Gionatan Danti [this message]
2018-10-19 13:08         ` Zdenek Kabelac
2018-10-19 13:16           ` Ilia Zykov
2018-10-19 17:00           ` Ilia Zykov
2018-10-22 10:54             ` Zdenek Kabelac
2018-10-19 20:54           ` Gionatan Danti

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