I'll be using allocation classes (devices) on v12. Now that v12 beta is here, I'd like to get testing. But obviously I need to size the underlying SSDs appropriately, to buy them. But how do I calculate what size metadata vdev I will need?
Note that for spacemap/metaslab efficiency I'm using non-standard metaslab count (~1000 per vdev) and spacemap block size (~16K), based on a Matt Ahrens BSDCan paper (I think?), if that matters.
Also I will be migrating data to a new pool with blank disks, on 12.0 (send/recv), to ensure that metadata is all split out to SSD.
Thanks
- How do I obtain the current total size of metadata (all of it - spacemaps, DDT, file system pointers & records, etc!) using the zdb or other commands?
- Is this the same as the amount of on-disk pool space that will be needed (MB/GB of disk space), or do I have 2 figures, one for "metadata size" and another for "on-disk metadata size", because of block sizes vs. data record sizes? If they are different, how do I find the amount of on-disk space currently used/needed?
Note that for spacemap/metaslab efficiency I'm using non-standard metaslab count (~1000 per vdev) and spacemap block size (~16K), based on a Matt Ahrens BSDCan paper (I think?), if that matters.
Also I will be migrating data to a new pool with blank disks, on 12.0 (send/recv), to ensure that metadata is all split out to SSD.
Thanks
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