On Fri, Dec 07, 2018 at 05:09:17AM -0800, L A Walsh wrote: > How difficult would it be to allow 26 more dump levels > in xfs dump/restore? Theoretically anyone using 0-9 > would see no change. Would there be some "problem" or > "gotcha" in adding in what would _seem_ to be a simple > change? Everything _seems_ simple with xfsdump. e.g. the inventory session headers supports up to 255 levels in it's on-disk format, but the xfsdump command is limited to just 10 levels by a separate "max level" define. IOWs, on the surface it _seems_ simple to change it, but I don't know all the places that the dump level is stored, nor what would happen if an older xfsdump/xfsrestore binary tripped over an inventory with a dump level larger than they were compiled to handle. I also don't know if there are scalability problems with resolving the contents of incremental dump levels. Certainly restoring from 30 incremental dumps is more onerous than 6-7, but that's just time. What I don't know is how the invenetory scales to more than 10 incremental and whether there's some exponential algorithm in there that falls apart. So there's a lot of testing that would be needed to validate what looks like a 1 line change to the code. So, yes, technically we could increase the dump level, but there's a *lot* of verification work after doing so and it's not a risk-free modification. FWIW, the idea behind 10 dump levels is that it is enough for a full dump every week w/ an incremental every night of the week until the next full dump is done on the weekend. What's the backup plan you want to use/need that requires a larger number of incrementals? Knowing what you want more dump levels for helps us understand how it would be used and what really needs to be testedi first.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
