On 7/12/22 09:39, Bart Van Assche wrote:
> On 7/11/22 16:11, Damien Le Moal wrote:
>> Do you have these cases:
>> 1) host-managed disks:
>> SWR zones are *mandatory* so there is at least one. Thus read capacity
>> will return either 0 if there are no conventional zones (they are
>> optional) or the total capacity of the set of contiguous conventional
>> zones starting at lba 0. In either case, read capacity does not give you
>> the actual total capacity and you have to look at the report zones reply
>> max lba field.
>
> Does the scsi_debug driver allow to create a host-managed disk with one
> or more conventional zones and one or more sequential write required zones?
As per specs, conventional zones are optional. SWR zones are mandatory.
See this code in sdebug_device_create_zones():
conv_capacity = (sector_t)sdeb_zbc_nr_conv << devip->zsize_shift;
if (conv_capacity >= capacity) {
pr_err("Number of conventional zones too large\n");
return -EINVAL;
}
devip->nr_conv_zones = sdeb_zbc_nr_conv;
devip->nr_seq_zones =
ALIGN(capacity - conv_capacity, devip->zsize) >>
devip->zsize_shift;
devip->nr_zones = devip->nr_conv_zones + devip->nr_seq_zones;
>
>> Note that anyway, there are no drives out there that use RC BASIS = 0. I
>> had to hack a drive FW to implement it to test this code...
>
> A JEDEC member is telling me that I should use RC BASIS = 0 for
> host-managed zoned storage devices that only have sequential write
> required zones. That sounds weird to me so I decided to take a look at
> how the sd_zbc.c code handles RC BASIS.
RC BASIS = 0 makes sense only for host-managed drives that have
conventional zones starting at LBA 0 *AND* want to have some sort of
backward compatibility with a regular disk by advertizing only the
capacity of these conventional zones (all together, the set of
conventional zones starting at LBA 0 can be used like a regular disk).
That is a fairly narrow use case that is in my opinion not useful at all
given that the device type differs from regular disks anyway. For
host-managed disks, RC BASIS = 1 makes more sense. All SMR disks I know of
on the market use that.
>
> Bart.
>
--
Damien Le Moal
Western Digital Research
