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Date:      Thu, 23 May 2013 11:00:21 +0200
From:      Albert Shih <Albert.Shih@obspm.fr>
To:        Paul Kraus <paul@kraus-haus.org>
Cc:        Ivailo Tanusheff <Ivailo.Tanusheff@skrill.com>, Liste FreeBSD <freebsd-questions@freebsd.org>
Subject:   Re: ZFS install on a partition
Message-ID:  <20130523090021.GD1426@pcjas.obspm.fr>
In-Reply-To: <A9599DD7-1A32-4607-BC83-2E6E4D03C560@kraus-haus.org>
References:  <F744BBF1-D98C-47BF-9546-14D1A9CB3733@todoo.biz> <372082cab2064846809615a8073e022c@DB3PR07MB059.eurprd07.prod.outlook.com> <A9599DD7-1A32-4607-BC83-2E6E4D03C560@kraus-haus.org>

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 Le 18/05/2013 ? 09:02:15-0400, Paul Kraus a écrit
> On May 18, 2013, at 3:21 AM, Ivailo Tanusheff
> <Ivailo.Tanusheff@skrill.com> wrote:
> 
> > If you use HBA/JBOD then you will rely on the software RAID of the
> > ZFS system. Yes, this RAID is good, but unless you use SSD disks to
> > boost performance and a lot of RAM the hardware raid should be more
> > reliable and mush faster.
> 
> 	Why will the hardware raid be more reliable ? While hardware raid is
> 	susceptible to uncorrectable errors from the physical drives
> 	(hardware raid controllers rely on the drives to report bad reads and
> 	writes), and the uncorrectable error rate for modern drives is such
> 	that with high capacity drives (1TB and over) you are almost certain
> 	to run into a couple over the operational life of the drive. 10^-14
> 	for cheap drives and 10^-15 for better drives, very occasionally I
> 	see a drive rated for 10^-16. Run the math and see how many TB worth
> 	of data you have to write and read (remember these failures are
> 	generally read failures with NO indication that a failure occurred,
> 	bad data is just returned to the system).
> 
> 	In terms of performance HW raid is faster, generally due to the cache
> 	RAM built into the HW raid controller. ZFS makes good use of system,

Before I'm installing my server under 9.0 + ZFS I do some benchmarks with
ionice to compare 

    FreeBSD 9.0+ ZFS + 12 disk SATA 7200 rpm vs CentOS + H700 + 12 disk SAS 15krpm

(Both are same Dell poweredge).

And the ZFS+12 disk sata goes much faster than CentOS+H700+ext4 almost everywhere. Only
for small file AND small record size the ZFS is slower than CentOS. 

The server don't have SSD. He got 48Go of ram. 

Regards.

JAS
-- 
Albert SHIH
DIO bâtiment 15
Observatoire de Paris
5 Place Jules Janssen
92195 Meudon Cedex
France
Téléphone : +33 1 45 07 76 26/+33 6 86 69 95 71
xmpp: jas@obspm.fr
Heure local/Local time:
jeu 23 mai 2013 10:53:50 CEST



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