linux-kernel - Re: [PATCH RFC v1 0/5] Add SCSI per device tagsets

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Date:   Fri, 18 Feb 2022 23:37:03 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     "Melanie Plageman (Microsoft)" <melanieplageman@...il.com>
Cc:     mikelley@...rosoft.com, jejb@...ux.ibm.com, kys@...rosoft.com,
        martin.petersen@...cle.com, mst@...hat.com,
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        kashyap.desai@...adcom.com, mpe@...erman.id.au,
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        andres@...razel.de
Subject: Re: [PATCH RFC v1 0/5] Add SCSI per device tagsets

On Fri, Feb 18, 2022 at 06:41:52PM +0000, Melanie Plageman (Microsoft) wrote:
> Currently a single blk_mq_tag_set is associated with a Scsi_Host. When SCSI
> controllers are limited, attaching multiple devices to the same controller is
> required. In cloud environments with relatively high latency persistent storage,
> requiring all devices on a controller to share a single blk_mq_tag_set
> negatively impacts performance.

So add more controllers instead of completely breaking the architecture.