From: David Brown <david.brown@hesbynett.no>
To: linux-raid@vger.kernel.org
Subject: Re: Direct disk access on IBM Server
Date: Thu, 21 Apr 2011 13:00:39 +0200 [thread overview]
Message-ID: <iop2oo$vs4$1@dough.gmane.org> (raw)
In-Reply-To: <BANLkTint14TBOaBqaaXrUggeJWMPShWA8A@mail.gmail.com>
On 21/04/11 05:50, Ryan Wagoner wrote:
> On Wed, Apr 20, 2011 at 7:24 AM, David Brown<david@westcontrol.com> wrote:
>> Pros for hardware raid:
>>
>> + It can have battery backup (I don't have one at the moment - I have an
>> excellent UPS for the whole system).
>> + Rebuilds will be handled automatically by just adding new disks
>> + The card supports online resizing and reshaping
>> + It looks like the card supports caching with an SSD
>> + The card supports snapshots of the virtual drives
>
> Unless the card allows you to enable the write cache without the
> backup battery you will not see the real performance of the card. This
> option is normally locked out to prevent data loss in case the system
> crashes, power is pulled, etc. An external UPS will not protect in all
> cases if you enable the write back cache without battery.
>
The write cache is allowed without the battery, but disabled by default.
I agree that even with an UPS there is still a risk - I guess that's why
it is disabled. But the risk is pretty minimal for me - there is no
realistic chance of the power plug being pulled, for example. Other
risks do exist - the power supply on the server may fail, the UPS may
fail, etc. In the end there are /always/ risks - even with a battery on
the raid card, it won't protect against everything. All I can do is
reduce the risks to a realistic minimum while keeping good performance
and features (and sensible cost!), and make sure I've got good backups
of everything.
> I have systems with both software raid and hardware raid. If the
> budget allows I tend to go the hardware raid route. When buying a
> Dell, HP, etc server with hardware raid you end up with a complete
> package. The enclosure, card, and server monitoring software make it
> easy to manage and visually see which drive has failed.
>
> Ryan
> --
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next prev parent reply other threads:[~2011-04-21 11:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-19 13:21 Direct disk access on IBM Server David Brown
2011-04-19 13:25 ` Mathias Burén
2011-04-19 14:04 ` David Brown
2011-04-19 14:07 ` Mathias Burén
2011-04-19 15:12 ` David Brown
2011-04-19 15:41 ` Mathias Burén
2011-04-20 8:08 ` David Brown
2011-04-19 20:08 ` Stan Hoeppner
2011-04-20 11:24 ` David Brown
2011-04-20 11:40 ` Rudy Zijlstra
2011-04-20 12:21 ` David Brown
2011-04-21 6:24 ` Stan Hoeppner
2011-04-21 11:36 ` David Brown
2011-04-23 14:05 ` Majed B.
2011-04-23 14:42 ` David Brown
2011-04-24 12:48 ` Drew
2011-04-24 20:00 ` David Brown
2011-04-24 20:25 ` Rudy Zijlstra
2011-04-25 9:42 ` David Brown
2011-04-21 3:50 ` Ryan Wagoner
2011-04-21 11:00 ` David Brown [this message]
2011-04-21 4:10 ` Stan Hoeppner
2011-04-21 11:19 ` David Brown
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