- From: Arno Wagner <me@xxxxxxxxxxx>
- Date: 7 May 2007 17:07:32 GMT
Previously gladwinchris@xxxxxxxxx wrote:
This solution is not high-availability. You can have lots of
temporary failures from PCs that are not running, laptops
that do not have Internet connectivity, etc..
Arno, your comments seem to be assuming that we are designing
Dispersed Storage to be hosted on devices like laptops that come and
go. This is not the focus of the initial release. Laptops and home
PCs can be clients for a Dispersed Storage grid, but they are not the
focus type of server.
The initial focus for servers for Cleversafe Dispersed Storage grids
are hosted servers whose availability would typically be around
99.9%. Hosting a Dispersed Storage grid on this class of servers
results in extremely available and reliable storage.
Aha, so initially you assure reliability by paying money for it.
When that runs out you then move to the chancy laptop and so
And, we actually are working on a yet-to-be-released version which will
reduce the blowup to ~1.3x.
This sounds to good to be true without some major drawback hidden
In order to realize a blowup of 1.3 (i.e. a storage overhead of 30%),
we are using methods like Reed-Solomon coding to get that level of
overhead at extremely high levels of reliability. These methods have
been around for decades and are widely used in communications.
But not for the types of failure you need to be able to deal with
in this application. I think you are being far too optimistic here.
Personally I think this is nice to play around with, but only a foolDispersed Storage was NOT is not being designed to be hosted on a
would depend on it. Also it is unusable for larger amounts of data. If
you store larger amounts of data, you get completely unrealistic
numbers of users that need to participate in this long-term.
federation of low availability devices, like laptops and home PCs.
Dispersed Storage IS designed for a hosting model like that of the
Internet. The Internet uses an open protocol -- TCP/IP, but is
typically provided as a commercial service by ISPs who use highly
available devices -- hosted routers -- to provide an inter-networking
service. Some larger organizations also host their own routers to
provide internal networking services.
That is BS. The Internet has a very low storage capacity, basically
the packets that are in flight. That is because it is an interconnect
system. The Internet consequentially has no hosting model at all,
although you can read things like this in nonsensical press articles
Cleversafe Dispersed Storage is designed for a model like the Internet
where a variety of companies like ISPs and hosting companies will
offer storage as a service using highly available devices -- storage
servers. In addition, some larger organizations will also use
Dispersed Storage to host their own storage services. You can also
use the open Dispersed Storage protocol to create a non-commercial
Dispersed Storage grid. When building a Dispersed Storage grid, we'd
recommend you use servers to build that grid, just like you'd want to
use highly available routers if you were building your own Internet.
Perhaps one day, you'll see mesh communications networks and mesh
storage networks built on very low reliability devices like laptops
that come and go a lot, but that is not the initial focus of
Cleversafe Dispersed Storage.
Fine. So if the servers are static and all are high-reliability,
what is new with this approach? You could just use ECC-file
and distribute the chunks over the different servers. Or even
simpler: Do RAID6 with 7 chunks, but each on its own,
high-reliability server, and you get an overhead of 1.4 and
a fault-tolerance of 2 on 7. There, all allready solved.
So tell me, why are you talking to private and small customers,
like you do here? And what is so new or exciting about your
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