First off, i’m not an AS developer/employee so i’m not really an expert when it comes to how they actually implemented something. I just googled up anything I could find about LDT’s when I had to decide on their usage and hope this may help you a bit with your data model.
First off, forget the mentioned 10kb. Been wrong. According to the sizing guide it should be closer to 40kb of record size for a full year.
(3653(28bytes bin meta+ 8bytes data)+overhead per record => ~40kb
If my understanding of LDT’s sub-records mechanism is correct, it will not update a block on the ssd but put the whole sub-record (containing a bunch of entries, according to doc’s “ranging from 2kb-200kb” in size) into the LFS system which tries to minify that block writing process using that write cache (not confirmed it actually does for LDT).
I assume, that it will have to (persistently) update the super-structure too, but without looking at the code it’s hard to tell whether it’s implemented like that. BTW, that super structure seems to have a size of ~220 bytes.
What I can’t tell you is how to make sure your sub-records are always minimal in size. I would ask that to AS engineers with that offering of a free 30 minutes modeling consulting.
To me, 40kb vs. 2kb (if possible to enforce) sounds worth the extra IOPS (IF ANY in your case, as small LDT’s fallback to some kind of compact mode, so there should be no tree traversal causing additional read OPs and super structure and the compact list could be stored together in the LDT bin…
That’s as far as my knowledge goes. So far I haven’t dug deeper in the code but the only reason I didn’t use LDTs in the beginning was that backup-issue but that one is fixed by now. Yeah, no XDR support but that isn’t an issue with the community version which lacks that feature anyways. Haven’t heard of plans about supporting that. But I’d guess if you are on enterprise and really want that feature, they would develop it for you.
P.S.: If you make any findings regarding this whole topic it would interest me too to hear about them. Idk, maybe an AS engineer will reply here aswell at some point.