Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
Subject: slow sync performance on LSI / Broadcom MegaRaid performance with
 battery cache
To:     Ric Wheeler <rwheeler@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        Chinmay V S <cvs268@gmail.com>
Cc:     "J. Bruce Fields" <bfields@fieldses.org>,
        Theodore Ts'o <tytso@mit.edu>, linux-fsdevel@vger.kernel.org,
        Al Viro <viro@zeniv.linux.org.uk>,
        LKML <linux-kernel@vger.kernel.org>,
        Matthew Wilcox <matthew@wil.cx>
References: <528CA73B.9070604@profihost.ag>
 <20131120125446.GA6284@infradead.org>
 <CAK-9PRAManphkxT3ub0DfW8hx=xbq+ZeqUB0E0CEnFTfF7AQuw@mail.gmail.com>
 <528CC36A.7080003@profihost.ag>
 <CAK-9PRDyGhXPef-Vbt83Os-oowFZ2HzSZVY9PH3rSdnTwNmf2w@mail.gmail.com>
 <20131120153703.GA23160@thunk.org> <20131120155507.GA5380@fieldses.org>
 <CAK-9PRCQ6qWvzpdvK8BswpS+TfgM7NeoRaVdChFHhyDjwtUGTw@mail.gmail.com>
 <20131120175807.GC5380@fieldses.org>
 <CAK-9PRDNxHAX70cN88kRt03FkYbDB_x1cFQQYmVzqiCX=aZD6w@mail.gmail.com>
 <20131121101101.GA18404@infradead.org> <528FB828.5000301@profihost.ag>
 <528FC09E.5090004@redhat.com> <5290F386.5040806@profihost.ag>
 <5291038E.4000908@redhat.com>
Message-ID: <acf161f8-2d78-544c-7c5b-8f92be74ab50@profihost.ag>
Date:   Wed, 8 Jan 2020 07:58:13 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.2.2
MIME-Version: 1.0
In-Reply-To: <5291038E.4000908@redhat.com>
Content-Type: text/plain; charset=windows-1252
Content-Language: de-DE
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hello list,

while we used adaptec controller with battery cache for years we
recently switched to dell hw using the perc controllers which are
rebranded lsi/broadcom controllers.

We're running btrfs subvolume / snapshot workloads and while those are
very fast on btrfs using a btrfs raid 0 on top of several raid 5 running
on adaptec (battery backed up) in write back mode.

The performance really sucks on those LSI controllers even the one i
have has 8GB cache instead of just 1GB at adaptec.

Especially sync / fsync are awfully slow taking sometimes 30-45 minutes
while btrfs is doing snapshots. The workload on all machines is the same
and the disks are ok.

Is there a way to disable FLUSH / sync at all for those devices? Just to
test?

I'm already using nobarrier mount option on btrfs but this does not help
either.

Thanks!

Greets,
Stefan