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From Sylvain Lebresne <>
Subject Re: No deletes - is periodic repair needed? I think not...
Date Mon, 27 Jan 2014 09:22:17 GMT
By periodic repair, I'll assume you mean "having to run repair every
gc_grace period to make sure no deleted entries resurrect". With that

> 1. Regular values, no deletes, no overwrites, write heavy, ttl's to manage
> size

Since 'repair within gc_grace' is about avoiding value that have been
deleted to resurrect, if you do no delete nor overwrites, you're in no risk
of that (and don't need to 'repair withing gc_grace').

> 2. Regular values, no deletes, some overwrites, read heavy (10 to 1),
> ttl's to manage size

It depends a bit. In general, if you always set the exact same TTL on every
insert (implying you always set a TTL), then you have nothing to worry
about. If the TTL varies (of if you only set TTL some of the times), then
you might still need to have some periodic repairs. That being said, if
there is no deletes but only TTLs, then the TTL kind of lengthen the period
at which you need to do repair: instead of needing to repair withing
gc_grace, you only need to repair every gc_grace + min(TTL) (where min(TTL)
is the smallest TTL you set on columns).

3. Counter values, no deletes, update heavy, rotation/truncation to manage
> size

No deletes and no TTL implies that your fine (as in, there is no need for
'repair withing gc_grace').


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