From mboxrd@z Thu Jan 1 00:00:00 1970 References: <20181205061938.vbkwk6ydnehacxml@chelmska.waw.pl> From: Zdenek Kabelac Message-ID: Date: Wed, 5 Dec 2018 15:23:21 +0100 MIME-Version: 1.0 In-Reply-To: <20181205061938.vbkwk6ydnehacxml@chelmska.waw.pl> Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] lvmcache writethrough synchronisation at system startup 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 , Marcin Wolcendorf Dne 05. 12. 18 v 7:19 Marcin Wolcendorf napsal(a): > Hi Everyone, > > Recently I have set up a simple lvmcache on my machine. This is a write-through > cache, so in my view it should never be necessary to copy data from the > cachepool to the origin LV. But this is exactly what happens: on system start > the > > lvs -o+cache_policy,cache_settings,cache_mode > > displays something like: > LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert CachePolicy CacheSettings CacheMode > home main Cwi-aoC--- 21.83t [cache1] [home_corig] 99.99 0.55 90.39 smq writethrough > > and for a next day or two it writes the whole cachepool to the origin. The data > on the cached LV seems fine as long as sha512 is concerned. > > Is this supposed to be that way? > > My setup: > I have 2 mdraid devices: one 24T raid6, one 1T raid1, and one separate SSD. All > are LUKS-encrypted, SSD is partitioned into MBR boot partition, encrypted /boot > partition and a big encrypted partition for a PV. The encrypted block devices > (except /boot) are PVs in my VG. The 24T RAID holds the origin LV, the 1T RAID > is made into a cachepool. Hi I'd say in your case it's very important which version of kernel is in use, as there very couple fixes solving this issue in not too long history. Secondary issue is - it's always good idea there is correct shutdown process instead of just 'power-off' althouhg in 'writethrough' case it should not be that big issue (but here applies the advice number one - use recent kernels). Regards Zdenek