Re: [9fans] fossil pb: FOUND!

["Aram Hăvărneanu" <aram.h@mgk.ro>]

>> How come? With venti, the address is the SHA-1 hash, with ZFS, you get
>> to chose the hash, but it can still be a hash.
>
> because in zfs the hash is not used as an address (lba).

But by this definition neither is venti. In venti, the hash is
translated to a lba by the index cache. In ZFS, the hash is translated
to a lba by the DDT (dedup-table). Both the Venti index cache and the
DDT can be regenerated from the data if they become corrupted.

> by all means, show us the numbers.  personally, i believe the mfgrs are not
> lying when they say that random i/o yields 1/10th the performance (at best)
> of sequential i/o.

I will, tomorrow.

> since you assert that it is ssds that make random i/o a non issue, and
> not caching, logically caching is not relevant to your point.

I've been trying to claim two things at the same time, these two
things are unrelated. Both SSDs and caching alleviate fragmentation
issues, in different ways.

> ps.  you're presenting a false choice between caching and fragmentation.
> case in point, ken's fs doesn't fragment as much as venti (and does not
> increase fragmentation over time) and yet it caches.

If that's the impression I made, I'm sorry for the misunderstanding
but that's not what I wanted. Of course there's no choice between
caching and fragmentation. Every filesystem caches.

-- 
Aram Hăvărneanu