From: Christoph Hellwig <hch@infradead.org>
To: Eric Wheeler <bcache@lists.ewheeler.net>
Cc: Christoph Hellwig <hch@infradead.org>,
Keith Busch <kbusch@kernel.org>, Coly Li <colyli@suse.de>,
Adriano Silva <adriano_da_silva@yahoo.com.br>,
Bcache Linux <linux-bcache@vger.kernel.org>,
Matthias Ferdinand <bcache@mfedv.net>,
linux-block@vger.kernel.org
Subject: Re: [RFC] Add sysctl option to drop disk flushes in bcache? (was: Bcache in writes direct with fsync)
Date: Fri, 27 May 2022 21:59:20 -0700 [thread overview]
Message-ID: <YpGsKDQ1aAzXfyWl@infradead.org> (raw)
In-Reply-To: <a2ed37b8-2f4a-ef7a-c097-d58c2b965af3@ewheeler.net>
On Fri, May 27, 2022 at 06:52:22PM -0700, Eric Wheeler wrote:
> Adriano who started this thread (cc'ed) reported that setting
> queue/write_cache to "write back" provides much higher latency on his NVMe
> than "write through"; I tested a system here and found the same thing.
>
> [...]
>
> Is this expected?
Once you do that, the block layer ignores all flushes and FUA bits, so
yes it is going to be a lot faster. But also completely unsafe because
it does not provide any data durability guarantees.
next prev parent reply other threads:[~2022-05-28 4:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <958894243.922478.1652201375900.ref@mail.yahoo.com>
[not found] ` <958894243.922478.1652201375900@mail.yahoo.com>
[not found] ` <9d59af25-d648-4777-a5c0-c38c246a9610@ewheeler.net>
2022-05-23 18:36 ` [RFC] Add sysctl option to drop disk flushes in bcache? (was: Bcache in writes direct with fsync) Eric Wheeler
2022-05-24 5:34 ` Christoph Hellwig
2022-05-24 20:14 ` Eric Wheeler
2022-05-24 20:34 ` Keith Busch
2022-05-24 21:34 ` Eric Wheeler
2022-05-25 5:20 ` Christoph Hellwig
2022-05-25 18:44 ` Eric Wheeler
2022-05-26 9:06 ` Christoph Hellwig
2022-05-28 1:52 ` Eric Wheeler
2022-05-28 3:57 ` Keith Busch
2022-05-28 4:59 ` Christoph Hellwig [this message]
[not found] ` <24456292.2324073.1653742646974@mail.yahoo.com>
[not found] ` <YpLmDtMgyNLxJgNQ@kbusch-mbp.dhcp.thefacebook.com>
[not found] ` <2064546094.2440522.1653825057164@mail.yahoo.com>
[not found] ` <YpTKfHHWz27Qugi+@kbusch-mbp.dhcp.thefacebook.com>
2022-06-01 19:27 ` Adriano Silva
2022-06-01 21:11 ` Eric Wheeler
2022-06-02 5:26 ` Christoph Hellwig
2022-05-25 5:17 ` Christoph Hellwig
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