From: Bart Van Assche <bvanassche@acm.org>
To: Jianlin Lv <iecedge@gmail.com>
Cc: jejb@linux.ibm.com, martin.petersen@oracle.com,
paulmck@kernel.org, bp@suse.de, peterz@infradead.org,
will@kernel.org, rdunlap@infradead.org, kim.phillips@amd.com,
rostedt@goodmis.org, wyes.karny@amd.com, jianlv@ebay.com,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-scsi@vger.kernel.org
Subject: Re: [PATCH] scsi: sd: support specify probe type of build-in driver
Date: Wed, 7 Jun 2023 10:07:00 -0700 [thread overview]
Message-ID: <e9b8b9c5-f400-9152-0f4b-537b05203dd2@acm.org> (raw)
In-Reply-To: <CAFA-uR_Zn4MdFKs6U6dqPjuVS60yN4RcYU4jJzjknqy7-RWyEQ@mail.gmail.com>
On 6/7/23 08:55, Jianlin Lv wrote:
> 1. MegaRAID adapters associated with 24 local disks. The disks are named
> sequentially as "sda," "sdb," and so on, up to "sdx."
> 2. STAT controllers associated with the root disk, named "sdy."
>
> Both the MegaRAID adapters and the SATA controller (PCH) are accessed via
> the PCIe bus. In theory, depending on their PCIe bus ID in ascending order,
> the devices should be initialized in ascending order as well.
Hmm ... I don't think there is anything that prevents the PCIe maintainer
from changing the PCIe probing behavior from synchronous to asynchronous?
In other words, I don't think it is safe to assume that PCIe devices are
always scanned in the same order.
> For cloud deployment, the local volume provisioner detects and creates PVs
> for each local disk (from sda to sdx) on the host, and it cleans up the
> disks when they are released.
> This requires the logical names of the disks to be deterministic.
I see two possible solutions:
- Change the volume provisioner such that it uses disk references that do
not depend on the probing order, e.g. /dev/disk/by-id/...
- Implement an algorithm in systemd that makes disk names predictable.
An explanation of how predictable names work for network interfaces is
available here: https://wiki.debian.org/NetworkInterfaceNames. The
systemd documentation about predictable network names is available here:
https://www.freedesktop.org/software/systemd/man/systemd.net-naming-scheme.html
These alternatives have the advantage that disk scanning remains asynchronous.
Thanks,
Bart.
next prev parent reply other threads:[~2023-06-07 17:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-06 5:12 [PATCH] scsi: sd: support specify probe type of build-in driver Jianlin Lv
2023-06-06 17:38 ` Bart Van Assche
2023-06-07 15:55 ` Jianlin Lv
2023-06-07 17:07 ` Bart Van Assche [this message]
2023-06-08 2:51 ` Jianlin Lv
2023-06-08 16:23 ` Bart Van Assche
2023-06-24 11:45 ` Jianlin Lv
2023-06-07 14:10 ` Christoph Hellwig
2023-06-08 3:10 ` Jianlin Lv
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