Frequently Asked Questions¶
Can I change the size of the zones of a device?¶
The size of the zones of a physical zoned device are fixed at manufacturing time by the device vendor. For a particular device model, it is not possible to change the zone size.
Device emulation software such as tcmu-runner allow defining zoned block devices with different zone sizes. While this does not replace the ability to change an existing device zone size, such solution allows exploring the impact of the device zone size on the application being developed.
With a host managed drive, how do I change the position of a zone write pointer?¶
The write pointer position of a zone changes automatically in response to the following commands.
- A write operation (regular write command, write same command, etc) issue with a starting LBA equal to the zone write pointer current location: the write pointer position advances by an amount of LBA equal to the amount of blocks written.
- A zone reset operation: the write pointer position of the zone is returned to the start of the zone.
- A disk format operation: the write pointer of all zones is reset.
No other command, operation or user action can change the position of a zone write pointer to any position within the zone.
How do I rewind the position of a zone write pointer?¶
As mentioned in the previous question reply, resetting a zone will rewind the zone write pointer position to the first LBA of the zone. A full disk format operation will also reset all zones.
How do I partially rewind the position of a zone write pointer?¶
This is not possible. A zone write pointer can only be moved back to the start LBA of the zone using a reset write pointer command.
Can I create partitions on my host managed disk?¶
It is possible but partitioning tools such as gparted to create GUID partition tables do not support host managed zoned disks that do not have a conventional zone at the end of the LBA space. If the last zone of the disk is a sequential write required zone, the secondary GPT header and table entries will not be writable at the end of the LBA space, that is, at the end of the last zone of the disk.
Linux® kernel mandates that partitions of a zoned block device be zone aligned. That is, the start sector of a disk partitions must be the start sector of a zone and the end sector of the partition must be the last sector of a zone.
Using the dm-linear device mapper target to isolate smaller portions of a large host managed disk can be a replacement solution.