From mboxrd@z Thu Jan 1 00:00:00 1970 References: <06b65c62-8ca2-0d29-b98d-1a1585141f81@redhat.com> <8ecbd3c8-4819-9ff2-40b1-315e6ae03c97@izyk.ru> <36f0f734-c49f-eaf9-7ff5-8aedfd7345b3@redhat.com> From: Gionatan Danti Message-ID: <707aafdc-cfd2-3bdd-13bb-1bfdc08c6ad9@assyoma.it> Date: Fri, 19 Oct 2018 14:45:02 +0200 MIME-Version: 1.0 In-Reply-To: <36f0f734-c49f-eaf9-7ff5-8aedfd7345b3@redhat.com> Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Why doesn't the lvmcache support the discard (trim) command? Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development , Zdenek Kabelac , Ilia Zykov 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