From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mimecast-mx02.redhat.com (mimecast04.extmail.prod.ext.rdu2.redhat.com [10.11.55.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 13E0910AF9CF for ; Sun, 8 Dec 2019 11:57:45 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 390F81006A90 for ; Sun, 8 Dec 2019 11:57:45 +0000 (UTC) MIME-Version: 1.0 Date: Sun, 08 Dec 2019 12:57:36 +0100 From: Gionatan Danti In-Reply-To: References: <1p3erjcoc4qsk3gplvduhoep.1575740265800@gmail.com> <24044.11058.338208.602498@quad.stoffel.home> Message-ID: <4851bf1ac6d1dca625598bbfe3a28b8c@assyoma.it> Content-Transfer-Encoding: 8bit Subject: Re: [linux-lvm] =?utf-8?q?Best_way_to_run_LVM_over_multiple_SW_RAIDs?= =?utf-8?q?=3F?= 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 Il 08-12-2019 00:14 Stuart D. Gathman ha scritto: > On Sat, 7 Dec 2019, John Stoffel wrote: > >> The biggest harm to performance here is really the RAID5, and if you >> can instead move to RAID 10 (mirror then stripe across mirrors) then >> you should be a performance boost. > > Yeah, That's what I do. RAID10, and use LVM to join together as JBOD. > I forgot about the raid 5 bottleneck part, sorry. > >> As Daniel says, he's got lots of disk load, but plenty of CPU, so the >> single thread for RAID5 is a big bottleneck. > >> I assume he wants to use LVM so he can create volume(s) larger than >> individual RAID5 volumes, so in that case, I'd probably just build a >> regular non-striped LVM VG holding all your RAID5 disks. Hopefully > > Wait, that's what I suggested! > >> If you can, I'd get more SSDs and move to RAID1+0 (RAID10) instead, >> though you do have the problem where a double disk failure could kill >> your data if it happens to both halves of a mirror. > > No worse than raid5. In fact, better because the 2nd fault always > kills the raid5, but only has a 33% or less chance of killing the > raid10. (And in either case, it is usually just specific sectors, > not the entire drive, and other manual recovery techniques can come > into > play.) While I agree with both (especially regarding RAID10), I propose another setup: and MD RAID0 of the eight MD RAID5 arrays. If I remember correctly, LVM striping code is based on device mapper rather than MD RAID code. Maybe the latter is more efficient at striping on fast NVMe drives? Regards. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8