From: "Guilherme G. Piccoli" <gpiccoli@canonical.com>
To: Bob Liu <bob.liu@oracle.com>, linux-raid@vger.kernel.org
Cc: linux-block@vger.kernel.org, dm-devel@redhat.com,
jay.vosburgh@canonical.com, neilb@suse.com,
songliubraving@fb.com
Subject: Re: [PATCH 1/2] md/raid0: Introduce new array state 'broken' for raid0
Date: Tue, 30 Jul 2019 09:18:54 -0300 [thread overview]
Message-ID: <000c20fe-3bcd-2dff-a5ab-9a294bdc7746@canonical.com> (raw)
In-Reply-To: <d730c417-a328-3df3-1e31-32b6df48b6ad@oracle.com>
On 30/07/2019 03:20, Bob Liu wrote:
> [...]
>> + * broken
>> + * RAID0-only: same as clean, but array is missing a member.
>> + * It's useful because RAID0 mounted-arrays aren't stopped
>> + * when a member is gone, so this state will at least alert
>> + * the user that something is wrong.
>
>
> Curious why only raid0 has this issue?
>
> Thanks, -Bob
Hi Bob, I understand that all other levels have fault-tolerance logic,
while raid0 is just a "bypass" driver that selects the correct
underlying device to send the BIO and blindly sends it. It's known to be
a performance-only /lightweight solution whereas the other levels aim to
be reliable.
I've quickly tested raid5 and rai10, and see messages like this on
kernel log when removing a device (in raid5):
[35.764975] md/raid:md0: Disk failure on nvme1n1, disabling device.
md/raid:md0: Operation continuing on 1 devices.
The message seen in raid10 is basically the same. As a (cheap)
comparison of the complexity among levels, look that:
<...>/linux-mainline/drivers/md# cat raid5* | wc -l
14191
<...>/linux-mainline/drivers/md# cat raid10* | wc -l
5135
<...>/linux-mainline/drivers/md# cat raid0* | wc -l
820
Cheers,
Guilherme
next prev parent reply other threads:[~2019-07-30 12:19 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 20:31 [PATCH 0/2] Introduce new raid0 state 'broken' Guilherme G. Piccoli
2019-07-29 20:31 ` [PATCH 1/2] md/raid0: Introduce new array state 'broken' for raid0 Guilherme G. Piccoli
2019-07-30 0:11 ` NeilBrown
2019-07-30 11:43 ` Guilherme G. Piccoli
2019-07-30 6:20 ` Bob Liu
2019-07-30 12:18 ` Guilherme G. Piccoli [this message]
2019-07-31 0:28 ` NeilBrown
2019-07-31 13:04 ` Guilherme G. Piccoli
2019-07-31 19:47 ` Song Liu
2019-07-31 19:43 ` Song Liu
2019-08-01 12:07 ` Guilherme G. Piccoli
2019-08-16 13:48 ` Guilherme G. Piccoli
2019-07-29 20:31 ` [PATCH 2/2] mdadm: " Guilherme G. Piccoli
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