3 ms·

> Splitting cold and hot data as much as possible into separate pages will make the job of the garbage collector easier. How do I tell my SSD to write stuff to

> Splitting cold and hot data as much as possible into separate pages will make the job of the garbage collector easier. How do I tell my SSD to write stuff to specific pages? You can't really tell the SSD to do anything except read, write, or trim LBAs. Does NVMe support this with its queues? > 27. Over-provisioning is useful for wear leveling and performance I thought most if not all SSDs were already overprovisioned. Does additional overprovisioning help? > To ensure that logical writes are truly aligned to the physical memory, you must align the partition to the NAND-flash page size of the drive. I think this is false. This assumes there is a one-to-one mapping of LBA to SSD PBA which you don't know. LBA 2048 could go to any PBA on any page/block/flash line in the unit and as things are written and rewritten, any correspondence that might happen due to sequential assignment of PBAs->LBAs would gradually diminish, IF you knew for sure that was happening in the first place. Because you wouldn't really know what the SSD is doing without reverse engineering or seeing the source code of firmware, unless there's things going on in NVMe land that are new and I don't yet know.

thfuran 4y ago
>I thought most if not all SSDs were already overprovisioned. Does additional overprovisioning help? I think a big extra helping of overprovisioning is one of the major differences between consumer and enterprise SSDs.
wtallis 4y ago
I wrote a series of articles that covered the new features defined for NVMe drives. The general pattern is that there are now lots of optional hints that drives and host systems can exchange about data placement, alignment and lifetime. But there are also alternative paradigms available like Zoned Storage that break compatibility to offer explicit control. These features are mostly only implemented in enterprise SSDs, and often only if a big customer specifically asks for them. https://www.anandtech.com/show/11436/nvme-13-specification-published-new-features https://www.anandtech.com/show/11436/nvme-13-specification-p... https://www.anandtech.com/show/14543/nvme-14-specification-published https://www.anandtech.com/show/14543/nvme-14-specification-p... https://www.anandtech.com/show/16702/nvme-20-specification-released https://www.anandtech.com/show/16702/nvme-20-specification-r... https://www.anandtech.com/show/15959/nvme-zoned-namespaces-explained https://www.anandtech.com/show/15959/nvme-zoned-namespaces-e...

thfuran 4y ago

>I thought most if not all SSDs were already overprovisioned. Does additional overprovisioning help? I think a big extra helping of overprovisioning is one of the major differences between consumer and enterprise SSDs.

wtallis 4y ago

I wrote a series of articles that covered the new features defined for NVMe drives. The general pattern is that there are now lots of optional hints that drives and host systems can exchange about data placement, alignment and lifetime. But there are also alternative paradigms available like Zoned Storage that break compatibility to offer explicit control. These features are mostly only implemented in enterprise SSDs, and often only if a big customer specifically asks for them. https://www.anandtech.com/show/11436/nvme-13-specification-published-new-features https://www.anandtech.com/show/11436/nvme-13-specification-p... https://www.anandtech.com/show/14543/nvme-14-specification-published https://www.anandtech.com/show/14543/nvme-14-specification-p... https://www.anandtech.com/show/16702/nvme-20-specification-released https://www.anandtech.com/show/16702/nvme-20-specification-r... https://www.anandtech.com/show/15959/nvme-zoned-namespaces-explained https://www.anandtech.com/show/15959/nvme-zoned-namespaces-e...