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From: Eugene Vikhman <>
Subject: [linux-lvm] lvmcache and bare mdadm arrays
Date: Wed, 16 Jan 2019 21:27:30 +0200	[thread overview]
Message-ID: <> (raw)

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I spent the last couple of days trying to set up a new server with 16 
sas drives for the main storage and 2 SSDs for caching it using lvmcache.

First I used mdadm to create raid10 on HDDs and raid1 on SSDs. Then I 
followed the steps from the lvmcache manpage and the lvcreate/lvconvert 
manpages to create the cache and the metadata LVs and convert them to a 
cache-pool. It went fine, "lvs -a" showed a normal cache-pool device. 
But the last step failed with an ambiguous error when I used lvconvert 
--type cache --cachepool vg/cache vg/slow. I tried playing with 
parameters and made sure that the error had nothing to do with them. For 
an unidentified reason ioctl failed saying it could not lock the device 

Today I tried setting up the raids with lvm itself and it all worked 
like a charm.

So my thought is maybe manpages should actually mention something about 
it and say "don't try setting up caching on a bare mdadm raid - it won't 

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                 reply	other threads:[~2019-01-16 19:27 UTC|newest]

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