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Date: Tue, 10 Dec 2024 11:58:22 +0100
From: hch <hch@lst.de>
To: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Cc: hch <hch@lst.de>, "Martin K. Petersen" <martin.petersen@oracle.com>,
	Nitesh Shetty <nj.shetty@samsung.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Javier Gonzalez <javier.gonz@samsung.com>,
	Matthew Wilcox <willy@infradead.org>,
	Keith Busch <kbusch@kernel.org>, Keith Busch <kbusch@meta.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
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	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
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	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"joshi.k@samsung.com" <joshi.k@samsung.com>
Subject: Re: [PATCHv10 0/9] write hints with nvme fdp, scsi streams
Message-ID: <20241210105822.GA3123@lst.de>
References: <yq1ed38roc9.fsf@ca-mkp.ca.oracle.com> <9d61a62f-6d95-4588-bcd8-de4433a9c1bb@acm.org> <yq1plmhv3ah.fsf@ca-mkp.ca.oracle.com> <8ef1ec5b-4b39-46db-a4ed-abf88cbba2cd@acm.org> <yq1jzcov5am.fsf@ca-mkp.ca.oracle.com> <CGME20241205081138epcas5p2a47090e70c3cf19e562f63cd9fc495d1@epcas5p2.samsung.com> <20241205080342.7gccjmyqydt2hb7z@ubuntu> <yq1a5d9op6p.fsf@ca-mkp.ca.oracle.com> <20241210071253.GA19956@lst.de> <2a272dbe-a90a-4531-b6a2-ee7c4c536233@wdc.com>
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On Tue, Dec 10, 2024 at 08:05:31AM +0000, Johannes Thumshirn wrote:
> > Generally agreeing with all you said, but do we actually have any
> > serious use case for cross-LU copies?  They just seem incredibly
> > complex any not all that useful.
> 
> One use case I can think of is (again) btrfs balance (GC, convert, etc) 
> on a multi drive filesystem. BUT this use case is something that can 
> just use the fallback read-write path as it is doing now.

Who uses multi-device file systems on multiple LUs of the same SCSI
target ơr multiple namespaces on the same nvme subsystem?