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From: Can Jeuleers <can.jeuleers@gmail.com>
To: Wols Lists <antlists@youngman.org.uk>,
	Pierre Wieser <pwieser@trychlos.org>,
	linux-raid@vger.kernel.org
Subject: Re: Migrating a RAID 5 from 4x2TB to 3x6TB ?
Date: Tue, 09 Jun 2015 21:18:59 +0200	[thread overview]
Message-ID: <55773C23.1010600@gmail.com> (raw)
In-Reply-To: <55773493.3050605@youngman.org.uk>

On 09/06/15 20:46, Wols Lists wrote:
> Please expand! Having read the article, it doesn't seem to say anything
> more than what is repeated time and time on this list - MAKE SURE YOUR
> DRIVES ARE DECENT RAID DRIVES.

Large RAID5 arrays are a bad idea because of the probability of
unrecoverable read errors occurring during a rebuild, which increases
with the size of the array.

Decent RAID drives will have better reliability than indecent-ones
(haha), but in absolute terms their URE rates are still going to
increase with array size.

> If you have ERC, then the odd "soft" read error doesn't matter. If you
> don't have ERC, then your data is at risk when you replace a drive, and
> it doesn't matter how big your drives are, it's the array size that matters.

Indeed. Pierre was proposing to further increase the size of his RAID5
array, and I was advising him against it because of the above.

  parent reply	other threads:[~2015-06-09 19:18 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1419435054.589.1433790714774.JavaMail.zimbra@wieser.fr>
2015-06-08 19:28 ` Migrating a RAID 5 from 4x2TB to 3x6TB ? Pierre Wieser
2015-06-08 20:10   ` Wols Lists
2015-06-09 18:33     ` Pierre Wieser
2015-06-09  5:23   ` Can Jeuleers
2015-06-09 18:46     ` Pierre Wieser
2015-06-09 19:06       ` Wols Lists
2015-06-09 19:15       ` Roman Mamedov
2015-06-09 18:46     ` Wols Lists
2015-06-09 19:06       ` Another Sillyname
2015-06-09 19:18       ` Can Jeuleers [this message]
2015-06-15 11:31       ` Wilson, Jonathan
     [not found]   ` <CAOS+5GHzBgx2DuDe0+RLgZj9Q1BZ944i-9q4NEERq66Sk78b2g@mail.gmail.com>
2015-06-09 18:26     ` Pierre Wieser
2015-06-10 19:37   ` Pierre Wieser
2015-06-15 10:46     ` Wilson, Jonathan
2015-06-15 21:45       ` Wols Lists

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