Re: Sharing disks amoung multiple software RAIDs

From: Alex Davis
Date: Thu May 01 2008 - 21:52:10 EST


--- On Thu, 5/1/08, Kasper Sandberg <lkml@xxxxxxxxxxx> wrote:

> From: Kasper Sandberg <lkml@xxxxxxxxxxx>
> Subject: Re: Sharing disks amoung multiple software RAIDs
> To: "Justin Piszcz" <jpiszcz@xxxxxxxxxxxxxxx>
> Cc: "Alex Davis" <alex14641@xxxxxxxxx>, linux-raid@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
> Date: Thursday, May 1, 2008, 9:39 PM
> On Thu, 2008-05-01 at 08:50 -0400, Justin Piszcz wrote:
> >
> > On Thu, 1 May 2008, Alex Davis wrote:
> >
> > > Is this a bad thing? I'm guessing that it is,
> but I want independent
> > > confirmation before I spoke to someone I know
> who's doing this.
> > >
> > > Thanks
> > >
> > >
> > >
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> >
> > What is the use case, why would you want to do that?
> > I have seen people on the list do it before, for
> example are you going to
> > be utilizing both raids at the same time? If so, I
> would advise against
> > it.
> >
> > What is the reasoning?
>
> I do this!
>
> is this really bad? i would surely like a list of reasons
> why..
>
> I do it because.. well.. first off, it allows me to have
> /boot on
> different raidlevel than / or /home without extra disks.
> secondly, it allows me to with the same disks use different
> filesystems.. for instance, it allows me to have /home
> encrypted with
> dm-crypt, while still raided.. Not that i would mind
> encrypting /
> and /home as 1 partition, but it creates a whole slew of
> issues with
> having to create initrd and stuff..
>
> I realize that performance probably suffers abit from this,
> but well..
> is there any stability or security wise risk? i mostly use
> raid1 and
> raid5 only..
>
I would guess if the RAIDs are heavily used simultaneously it could
cause the disk head actuators to jump around more, causing more wear
and tear.


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