From: Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>
To: David Brown <david.brown@hesbynett.no>
Cc: Alex <creamyfish@gmail.com>, "H. Peter Anvin" <hpa@zytor.com>,
linux-raid@vger.kernel.org
Subject: Re: Is this enough for us to have triple-parity RAID?
Date: Fri, 20 Apr 2012 23:01:06 +0200 [thread overview]
Message-ID: <20120420210106.GA2432@lazy.lzy> (raw)
In-Reply-To: <4F91B1C4.5080205@hesbynett.no>
Hi again David,
> Yes, being a generator for GF(2^8) is a requirement for a parity
> generator (sorry for the confusing terminology here - if anyone has
> a better suggestion, please say) to be part of a 255 data disk
> system. However, being a GF generator is necessary but not
> sufficient - using parity generators (1, 2, 4, 16) will /not/ give
> quad parity for 255 data disks, even though individually each of 1,
> 2, 4 and 16 are generators for GF.
I ask again, could you please elaborate this?
I nowhere found such a further constrain for the parities.
All I could find is that the Vandermonde matrix must
be done with generators.
> 255 data disks is the theoretical limit for GF(2⁸). But it is a
> theoretical limit of the algorithms - I don't know whether Linux md
> raid actually supports that many disks. I certainly doubt if it is
> useful.
The reason to use many disks is in case of
geo-redundant RAID, for example with iscsi.
In this situation you want to have a lot of
redundance, in parities, not mirror.
bye,
--
piergiorgio
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2012-04-20 21:01 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-17 6:11 Is this enough for us to have triple-parity RAID? Alex
2012-04-17 7:58 ` David Brown
2012-04-17 16:37 ` Stefan /*St0fF*/ Hübner
2012-04-18 14:15 ` Alex
2012-04-18 14:11 ` David Brown
2012-04-17 17:16 ` Piergiorgio Sartor
2012-04-17 20:18 ` David Brown
2012-04-17 20:54 ` Piergiorgio Sartor
2012-04-18 18:22 ` Piergiorgio Sartor
2012-04-18 20:20 ` David Brown
2012-04-18 20:39 ` Piergiorgio Sartor
2012-04-19 18:16 ` H. Peter Anvin
2012-04-20 2:27 ` Alex
2012-04-20 3:00 ` H. Peter Anvin
2012-04-20 3:32 ` Alex
2012-04-20 18:58 ` David Brown
2012-04-20 19:39 ` H. Peter Anvin
2012-04-20 21:04 ` Piergiorgio Sartor
2012-04-20 21:01 ` Piergiorgio Sartor [this message]
2012-04-20 21:29 ` Peter Grandi
2012-04-20 22:31 ` Piergiorgio Sartor
2012-04-21 9:51 ` Peter Grandi
2012-04-21 11:18 ` Piergiorgio Sartor
2012-04-22 3:14 ` Alex
2012-04-22 8:57 ` Piergiorgio Sartor
2012-04-20 7:45 ` Stan Hoeppner
2012-04-23 15:26 ` Alex
2012-04-25 1:20 ` Stan Hoeppner
2012-04-25 2:45 ` Alex
2012-04-25 16:59 ` Emmanuel Noobadmin
2012-04-25 19:29 ` David Brown
2012-04-26 2:30 ` Alex
2012-04-27 15:15 ` Emmanuel Noobadmin
2012-05-01 16:38 ` Alex
2012-04-26 4:24 ` Alex
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120420210106.GA2432@lazy.lzy \
--to=piergiorgio.sartor@nexgo.de \
--cc=creamyfish@gmail.com \
--cc=david.brown@hesbynett.no \
--cc=hpa@zytor.com \
--cc=linux-raid@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).