netdev - Re: POHMELFS high performance network filesystem. Transactions, failover, performance.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 14 May 2008 06:35:19 -0700 (PDT)
From:	Sage Weil <sage@...dream.net>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Jeff Garzik <jeff@...zik.org>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: POHMELFS high performance network filesystem. Transactions,
 failover, performance.

> > What is your opinion of the Paxos algorithm?
> 
> It is slow. But it does solve failure cases.

For writes, Paxos is actually more or less optimal (in the non-failure 
cases, at least).  Reads are trickier, but there are ways to keep that 
fast as well.  FWIW, Ceph extends basic Paxos with a leasing mechanism to 
keep reads fast, consistent, and distributed.  It's only used for cluster 
state, though, not file data.

I think the larger issue with Paxos is that I've yet to meet anyone who 
wants their data replicated 3 ways (this despite newfangled 1TB+ disks not 
having enough bandwidth to actualy _use_ the data they store).  
Similarly, if only 1 out of 3 replicas is surviving, most people want to 
be able to read their data, while Paxos demands a majority to ensure it is 
correct.  (This is why Paxos is typically used only for critical cluster 
configuration/state, not regular data.)

sage
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html