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From: Hannes Reinecke <hare@suse.de>
To: Douglas Gilbert <dgilbert@interlog.com>, linux-scsi@vger.kernel.org
Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com,
	Damien.LeMoal@wdc.com
Subject: Re: [PATCH v3 02/15] scsi_debug: add doublestore option
Date: Fri, 21 Feb 2020 10:46:50 +0100	[thread overview]
Message-ID: <d1d70477-aa64-5ad4-3b35-531504e71ead@suse.de> (raw)
In-Reply-To: <20200220200838.15809-3-dgilbert@interlog.com>

On 2/20/20 9:08 PM, Douglas Gilbert wrote:
> The scsi_debug driver has always been restricted to using one
> (or none) ramdisk image for its storage. This means that thousands
> of scsi_debug devices can be created without exhausting the host
> machine's RAM. The downside is that all scsi_debug devices share
> the same ramdisk image. This option doubles the amount of ramdisk
> storage space with the first, third, fifth (etc) created
> scsi_debug devices using the first ramdisk image while the second,
> fourth, sixth (etc) created scsi_debug devices using the second
> ramdisk image.
> 
> The reason for doing this is to check that (partial) disk to disk
> copies based on scsi_debug devices have actually worked properly.
> As an example: assume /dev/sdb and /dev/sg1 are the same
> scsi_debug device, while /dev/sdc and /dev/sg2 are also the
> same scsi_debug device. With doublestore=1 they will have
> different ramdisk images. Then the following pseudocode could
> be executed to check the if sgh_dd copy worked:
>     dd if=/dev/urandom of=/dev/sdb
>     sgh_dd if=/dev/sg1 of=/dev/sg2 [plus option(s) to test]
>     cmp /dev/sdb /dev/sdc
> 
> If the cmp fails then the copy has failed (or some other
> mechanism wrote to /dev/sdb or /dev/sdc in the interim).
> 
> Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
> ---
>  drivers/scsi/scsi_debug.c | 264 +++++++++++++++++++++++++++-----------
>  1 file changed, 186 insertions(+), 78 deletions(-)
> 
Nice use-case, but really should be documented somewhere.
Otherwise:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer

  reply	other threads:[~2020-02-21  9:46 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-20 20:08 [PATCH v3 00/15] host managed ZBC + doublestore Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 01/15] scsi_debug: randomize command completion time Douglas Gilbert
2020-02-21  9:45   ` Hannes Reinecke
2020-02-20 20:08 ` [PATCH v3 02/15] scsi_debug: add doublestore option Douglas Gilbert
2020-02-21  9:46   ` Hannes Reinecke [this message]
2020-02-21 15:37     ` Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 03/15] scsi_debug: implement verify(10), add verify(16) Douglas Gilbert
2020-02-21  9:49   ` Hannes Reinecke
2020-02-20 20:08 ` [PATCH v3 04/15] scsi_debug: weaken rwlock around ramdisk access Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 05/15] scsi_debug: improve command duration calculation Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 06/15] scsi_debug: implement pre-fetch commands Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 07/15] scsi_debug: expand zbc support Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 08/15] scsi_debug: add zone commands Douglas Gilbert
2020-02-21  9:44   ` Johannes Thumshirn
2020-02-23  5:59     ` Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 09/15] scsi_debug: zbc module parameter Douglas Gilbert
2020-02-21  9:49   ` Johannes Thumshirn
2020-02-21 15:37     ` Douglas Gilbert
2020-02-22  8:27       ` Johannes Thumshirn
2020-02-20 20:08 ` [PATCH v3 10/15] scsi_debug: re-arrange parameters alphabetically Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 11/15] scsi_debug: zbc parameter can be string Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 12/15] scsi_debug: zone_max_open module parameter Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 13/15] scsi_debug: zone_nr_conv " Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 14/15] scsi_debug: zone_size_mb " Douglas Gilbert
2020-02-20 20:08 ` [PATCH v3 15/15] scsi_debug: bump to version 1.89 Douglas Gilbert
2020-02-20 20:11 ` [PATCH v3 00/15] scsi_debug: host managed ZBC + doublestore Douglas Gilbert

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