Re: Migrating a RAID 5 from 4x2TB to 3x6TB ?

From: Roman Mamedov <rm@romanrm.net>
To: Pierre Wieser <pwieser@trychlos.org>
Cc: Can Jeuleers <can.jeuleers@gmail.com>, linux-raid@vger.kernel.org
Subject: Re: Migrating a RAID 5 from 4x2TB to 3x6TB ?
Date: Wed, 10 Jun 2015 00:15:44 +0500	[thread overview]
Message-ID: <20150610001544.484da3a6@natsu> (raw)
In-Reply-To: <1222347192.1017.1433875572719.JavaMail.zimbra@wieser.fr>

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On Tue, 9 Jun 2015 20:46:12 +0200 (CEST)
Pierre Wieser <pwieser@trychlos.org> wrote:

> Does linux-raid have any recommandation(s) when managing more than 10TB of data ?
> 
> I may imagine:
> - several smaller RAID 5 devices
> - would RAID10 be a valuable solution in your opinion ?

The solution is called RAID6.

And don't go for overly large drives, e.g. 6x2TB is better than 4x3TB.

1) smaller drives might use more proven technology, require less precision, so
might be more reliable (at least according to hearsay and urban legends);

2) you need a considerable array member count anyway, to justify "losing" two
drives for parity in RAID6.

"But my enclosure only fits 4 drives". "But I don't have enough SATA ports".

Get a bigger enclosure. Get a second/third SATA controller. :)

-- 
With respect,
Roman

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