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mutable store on mirage?

  • To: Mirage List <cl-mirage@xxxxxxxxxxxxxxx>
  • From: Christopher Greenhalgh <Chris.Greenhalgh@xxxxxxxxxxxxxxxx>
  • Date: Wed, 16 Oct 2013 18:55:40 +0100
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  • List-id: MirageOS development <cl-mirage.lists.cam.ac.uk>
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  • Thread-topic: mutable store on mirage?

is there currently a sensible option for a mutable datastore in mirage? 
i'd like to make an interactive web site/service and need at least the 
equivalent of a persistent mutable key-value store with user-defined keys (e.g. 
to take a minimal example, key = user ID, value = current user profile 

a) I guess i could port baardskeerder - has that been done already?

b) 've had a look at irminsule, but 
b.1) at the moment i don't actually get how you would use it in this kind of 
scenario, e.g. does my user defined key (e.g. user login) map to a tag and a 
value (e.g. their current profile information) to a value? or does the whole 
current key/value state (i.e. user ID/value for all current users) map to a 
single value and the 'current state' to a single tag? or something else?? 
b.2) is there currently a mirage (non-unix) backend for it?

c) in a previous incarnation of mirage i started to write a mutable (strictly 
append only) key/value over that version of blkif, but ran out of time/energy; 
is this obviously a waste of time/duplication of effort or would it be 

d.1) is there any reason for/against persisting directly against blkif in 
mirage? i,e, with not filesystem abstraction?
d.2) as far as i can see the only up-to-date filesystem in mirage is the crunch 
RO fs; the fat fs is mostly there but need porting to the latest blkif 
interface, and there aren't any others at the moment - is that right?!

e) the mirage-unix OS has a skeleton blkif (over file) implementation but this 
is currently unimplemented; is it worth implementing and using this for posix 
or do we expect to use something like dave's ocaml xen-block-driver and 
xen-disk to emulate block devices from files instead even on posix targets?

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