From: Andy Smith <andy@lug.org.uk>
To: linux-raid@vger.kernel.org
Subject: Re: RAID 5 of RAID 5's?
Date: Mon, 13 Jun 2005 10:03:39 +0000 [thread overview]
Message-ID: <20050613100339.GO750@strugglers.net> (raw)
In-Reply-To: <42AD329B.4080103@apartia.fr>
[-- Attachment #1: Type: text/plain, Size: 896 bytes --]
On Mon, Jun 13, 2005 at 09:15:39AM +0200, Laurent CARON wrote:
> Dan Stromberg a ?crit :
> >>>Has anyone constructed a RAID 5 of RAID 5's using mdadm on a linux
> >>>system?
> >>>
> >>>Was it reliable?
> >>>
> >>>How large was it?
> >
> RAID 10 is IMHO a bit more efficient.
>
> Raid 5 means at least 9 disks:
> Usable capacity: 4 Disks
> Read speed: Good
> Write speed: poor
With a low number of disks, you would indeed get the same or less
capacity with RAID 5 + RAID 5 as compared to RAID 10, but as the
number of disks gets higher, doesn't the capacity of RAID 5 on top
of RAID 5 (we need a name for this, is RAID 55 technically correct?)
get better?
For example, 30 disks, organised as 10 3-disk RAID 5s, have 9*2 or
18 disks of capacity, whereas a RAID 10 of same would be 15 disks.
The write performance seems bad though, and maybe the rebuild time
as well.
[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 189 bytes --]
prev parent reply other threads:[~2005-06-13 10:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-07 23:39 RAID 5 of RAID 5's? Dan Stromberg
2005-06-10 7:11 ` Laurent CARON
2005-06-10 15:42 ` Brad Dameron
2005-06-10 20:43 ` Dan Stromberg
2005-06-12 0:45 ` Andy Smith
2005-06-13 17:55 ` Dan Stromberg
2005-06-13 7:15 ` Laurent CARON
2005-06-13 10:03 ` Andy Smith [this message]
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=20050613100339.GO750@strugglers.net \
--to=andy@lug.org.uk \
--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).