Re: [LSF/MM/BPF TOPIC] Hybrid SMR HDDs / Zone Domains & Realms

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On 3/2/23 19:26, Bart Van Assche wrote:
On 3/1/23 18:03, Damien Le Moal wrote:
But that is the issue: zones in the middle of each domain can be
activated/deactivated dynamically using zone activate command. So there is always the possibility of ending up with a swiss cheese lun, full of hole of unusable LBAs because the other domains (other LUN) activated some zones which
deactivate the equivalent zone(s) in the other domain.

With your idea, the 2 luns would not be independent as they both would be using LBAs are mapped against a single set of physical blocks. Zone activate command allows controlling which domains has the mapping active. So activating a zone in one domains results in the zone[s] using the same mapping in the other domain to
be deactivated.

Hi Damien,

Your reply made me realize that I should have provided more information. What I'm proposing is the following:
* Do not use any of the domains & realms features from ZBC-2.
* Do not make any zones visible to the host before configuration of the logical units has finished. Only make the logical units visible to the host after configuration of the logical units has finished. Do not support reconfiguration of the logical units while these are in use by the host.
* Only support active zones. Do not support inactive zones.
* Introduce a new mechanism for configuring the logical units.

This is not a new idea. The approach described above is already supported since considerable time by UFS devices. The provisioning mechanism supported by UFS devices is defined in the UFS standard and is not based on SCSI commands.

That really cries out for a device-mapper target.
Providing several LUNs only make sense if the hardware supports it; we've learned that lesson when developing support for Multi-actuator HDDs. If you want to have several logical disks without hardware support for it device-mapper is the way to go.

Cheers,

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




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