[prev in list] [next in list] [prev in thread] [next in thread] 

List:       dragonfly-users
Subject:    
From:       Unknown
Date:       2009-01-14 13:59:34
Message-ID: D4EB077A-EB40-48A9-A0B3-F8559B86E6CE () yberwaffe ! com
[Download RAW message or body]

om> <0E59E23F-6F9E-496A-9F38-2B49C527B815@opera.com>
From: Jasse Jansson <jasse@yberwaffe.com>
Subject: Re: RAID 1 or Hammer
Date: Wed, 14 Jan 2009 14:52:51 +0100
BestServHost: crater.dragonflybsd.org
List-Post: <mailto:users@crater.dragonflybsd.org>
List-Subscribe: <mailto:users-request@crater.dragonflybsd.org?body=subscribe>
List-Unsubscribe: <mailto:users-request@crater.dragonflybsd.org?body=unsubscribe>
List-Help: <mailto:users-request@crater.dragonflybsd.org?body=help>
List-Owner: <mailto:owner-users@crater.dragonflybsd.org>
MIME-Version: 1.0 (Apple Message framework v753.1)
Content-Type: text/plain; charset=ISO-8859-1; delsp=yes; format=flowed
Content-Transfer-Encoding: quoted-printable
In-Reply-To: <0E59E23F-6F9E-496A-9F38-2B49C527B815@opera.com>
Sender: users-errors@crater.dragonflybsd.org
Errors-To: users-errors@crater.dragonflybsd.org
Lines: 63
NNTP-Posting-Host: 216.240.41.25
X-Trace: 1231941709 crater_reader.dragonflybsd.org 883 216.240.41.25
Xref: crater_reader.dragonflybsd.org dragonfly.users:11897


On Jan 14, 2009, at 2:05 PM, Bjørn Vermo wrote:

>
> On 14. jan.. 2009, at 12.17, Jasse Jansson wrote:
>
>> First of all, thanks Simon for the links, It sure was interesting  
>> reading.
>>
>> On Jan 14, 2009, at 11:45 AM, Bjørn Vermo wrote:
>>
>>> I have toyed with the idea that one drive in a mirrored pair  
>>> ought to have the addresses inverted, so sector 1 on one drive is  
>>> mapped to sector MAX -1 on the other.
>>
>> I read it like the locality (radius) of the errors occur on the  
>> same disc,
>> so I don't see the benefit from your "reversed mirror strategy".
>
> He clearly stated that some drives models had error spikes at  
> certain cluster numbers.
> This should not really surprise anybody who is familiar with the  
> way modern drives work internally. The cylinder where you change to  
> a different data density is a border case, and any border cases  
> open extra bug opportunities.

That's true.

>
>>
>>
>> You will also get some interesting performance problems to tackle,  
>> when
>> one disc works on the inner tracks and the other one is on the  
>> outer tracks.
>
>
> A smart controller could make that into an opportunity. It is  
> hardly any more difficult than staggered stripes, which is widely  
> implemented.
>
> In most mirroring controllers I have seen the system will get the  
> read data from the first drive that has them ready. Two "opposite"  
> drives should be able to offer a better average read performance.

Sure, reads is no problem.
I was thinking about write performance and possible sync windows,
but I didn't spell it out. My bad.



Kaiser Jasse -- Authorized Stealth Oracle

The axioms of wisdom:
1. Go the SPARC way of life
2. You can't conquer the universe without the knowledge of FORTRAN
3. In the Unix realm, 10% of work fixes 90% of the problems






[prev in list] [next in list] [prev in thread] [next in thread]