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From: Roman Mamedov <rm@romanrm.net>
To: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
Cc: linux-block@vger.kernel.org, Song Liu <songliubraving@fb.com>,
	NeilBrown <neilb@suse.com>,
	linux-raid@vger.kernel.org, dm-devel@redhat.com,
	jay.vosburgh@canonical.com
Subject: Re: [PATCH] md/raid0: Fail BIOs if their underlying block device is gone
Date: Tue, 30 Jul 2019 01:18:50 +0500	[thread overview]
Message-ID: <20190730011850.2f19e140@natsu> (raw)
In-Reply-To: <20190729193359.11040-1-gpiccoli@canonical.com>

On Mon, 29 Jul 2019 16:33:59 -0300
"Guilherme G. Piccoli" <gpiccoli@canonical.com> wrote:

> Currently md/raid0 is not provided with any mechanism to validate if
> an array member got removed or failed. The driver keeps sending BIOs
> regardless of the state of array members. This leads to the following
> situation: if a raid0 array member is removed and the array is mounted,
> some user writing to this array won't realize that errors are happening
> unless they check kernel log or perform one fsync per written file.
> 
> In other words, no -EIO is returned and writes (except direct ones) appear
> normal. Meaning the user might think the wrote data is correctly stored in
> the array, but instead garbage was written given that raid0 does stripping
> (and so, it requires all its members to be working in order to not corrupt
> data).

If that's correct, then this seems to be a critical weak point in cases when
we have a RAID0 as a member device in RAID1/5/6/10 arrays.

-- 
With respect,
Roman

WARNING: multiple messages have this Message-ID (diff)
From: Roman Mamedov <rm@romanrm.net>
To: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
Cc: linux-raid@vger.kernel.org, linux-block@vger.kernel.org,
	dm-devel@redhat.com, jay.vosburgh@canonical.com,
	NeilBrown <neilb@suse.com>, Song Liu <songliubraving@fb.com>
Subject: Re: [PATCH] md/raid0: Fail BIOs if their underlying block device is gone
Date: Tue, 30 Jul 2019 01:18:50 +0500	[thread overview]
Message-ID: <20190730011850.2f19e140@natsu> (raw)
In-Reply-To: <20190729193359.11040-1-gpiccoli@canonical.com>

On Mon, 29 Jul 2019 16:33:59 -0300
"Guilherme G. Piccoli" <gpiccoli@canonical.com> wrote:

> Currently md/raid0 is not provided with any mechanism to validate if
> an array member got removed or failed. The driver keeps sending BIOs
> regardless of the state of array members. This leads to the following
> situation: if a raid0 array member is removed and the array is mounted,
> some user writing to this array won't realize that errors are happening
> unless they check kernel log or perform one fsync per written file.
> 
> In other words, no -EIO is returned and writes (except direct ones) appear
> normal. Meaning the user might think the wrote data is correctly stored in
> the array, but instead garbage was written given that raid0 does stripping
> (and so, it requires all its members to be working in order to not corrupt
> data).

If that's correct, then this seems to be a critical weak point in cases when
we have a RAID0 as a member device in RAID1/5/6/10 arrays.

-- 
With respect,
Roman

  reply	other threads:[~2019-07-29 20:18 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-29 19:33 [PATCH] md/raid0: Fail BIOs if their underlying block device is gone Guilherme G. Piccoli
2019-07-29 19:33 ` Guilherme G. Piccoli
2019-07-29 20:18 ` Roman Mamedov [this message]
2019-07-29 20:18   ` Roman Mamedov
2019-07-29 20:27   ` Guilherme G. Piccoli
2019-07-29 20:27     ` Guilherme G. Piccoli
2019-07-29 20:36     ` Roman Mamedov
2019-07-29 20:36       ` Roman Mamedov
2019-07-29 20:49       ` Guilherme G. Piccoli
2019-07-29 20:49         ` Guilherme G. Piccoli
2019-07-29 21:14     ` Reindl Harald
2019-07-29 21:14       ` Reindl Harald
2019-07-30  0:08 ` NeilBrown
2019-07-30  0:08   ` NeilBrown
2019-07-30 12:30   ` Guilherme G. Piccoli
2019-07-30 12:30     ` Guilherme G. Piccoli
2019-07-31 19:54     ` Song Liu
2019-07-31 19:54       ` Song Liu
2019-07-31 19:56       ` Song Liu
2019-07-31 19:56         ` Song Liu
2019-08-01 20:28         ` Guilherme G. Piccoli
2019-08-01 20:28           ` Guilherme G. Piccoli
2019-08-01 22:43           ` Song Liu
2019-08-01 22:43             ` Song Liu
2019-08-16 13:45             ` Guilherme G. Piccoli
2019-08-16 13:45               ` Guilherme G. Piccoli

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