Re: Sharing disks amoung multiple software RAIDs

[Alex Davis]

--- On Fri, 5/2/08, Kasper Sandberg <lkml@xxxxxxxxxxx> wrote:

> From: Kasper Sandberg <lkml@xxxxxxxxxxx>
> Subject: Re: Sharing disks amoung multiple software RAIDs
> To: "David Greaves" <david@xxxxxxxxxxxx>
> Cc: "David Rees" <drees76@xxxxxxxxx>, "David Lethe" <david@xxxxxxxxxxxx>, alex14641@xxxxxxxxx, "Justin Piszcz" <jpiszcz@xxxxxxxxxxxxxxx>, linux-raid@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
> Date: Friday, May 2, 2008, 5:43 PM
> On Fri, 2008-05-02 at 09:25 +0100, David Greaves wrote:
> > Kasper Sandberg wrote:
> > > Im not treating it as a backup, what i want, is
> to make sure that if 1
> > > disk dies, the data is still intact and ill
> hopefully be able to run
> > > with 1 disk till the newly ordered one arrives
> > Probably one of the main design objectives behind
> RAID/md
> 
> Exactly, but once people start saying: "Look how many
> problems people
> post to the thread on
> a weekly basis where people lose their data when md
> rebuilds go bad with
> non-shared disks" i begin to worry..
> 
> > 
> > > So my question remains.. Is md raid1 not suited
> for this need? would it
> > > be safer to run in non-raid1 mode and daily(maybe
> hourly) rsync
> > > everything over to the second disk?
> > 
> > md is 100% guaranteed perfect or your money back...
> > rsync is 100% guaranteed perfect or your money back...
> > your backups are 100% guaranteed perfect or your money
> back...
> > your hard drives are 100% guaranteed perfect or your
> money back...
> > your CPU and RAM are 100% guaranteed perfect or your
> money back...
> > your CPU and PSU fans are 100% guaranteed perfect or
> your money back...
> > 
> > Clearly if you want to panic over reliability you have
> lots of choices :)
> 
> I do not wish to panic, i merely wished to know if linux MD
> is believed
> to work in most cases, or believed to do all sorts of weird
> stuff when
> resyncing :)
> 
> > 
> > David
> > PS, FWIW md has saved my data* countless times over
> the past 'n' years in
> > exactly the scenario you describe.
> 
> It has also been useful to people i know, i just wished to
> be sure :)
> and as Keld Jørn Simonsen and Helge Hafting's comments
> seems to confirm,
> linux md IS nice and stable :)
> 
> and as said, what im looking for isnt an in-box backup
> solution, merely
> safety in case one disk burns :)
> 
> > 
> > *(or more accurately has saved me from having to
> restore my data)

Just to add another data point, I've been using md in RAID 5 configuration for ~3 years with dedicated USB and SATA disks 
(not mixed) and have had disks go bad, and have yet to lose 
any data. Given the 'quality' of high-capacity disks nowadays,
RAIDing them is the right thing to do.


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