Re: raid-0 with mdadm vs lvm striping

[Goswin von Brederlow <goswin-v-b@web.de>]

"Guy Watkins" <linux-raid@watkins-home.com> writes:

> } -----Original Message-----
> } From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
> } owner@vger.kernel.org] On Behalf Of Goswin von Brederlow
> } Sent: Wednesday, August 12, 2009 10:09 PM
> } To: Billy Crook
> } Cc: Henry, Andrew; goswin-v-b@web.de; Drew; linux-raid@vger.kernel.org
> } Subject: Re: raid-0 with mdadm vs lvm striping
> } 
> } Billy Crook <billycrook@gmail.com> writes:
> } 
> } > On Wed, Aug 12, 2009 at 04:14, Henry, Andrew<andrew.henry@logica.com>
> } wrote:
> } >> That's what my question was:  Will raid0 (striping) be faster or easier
> } to manage than lvm striping
> } >
> } > LVM striping won't change performance for small files. (That is files,
> } > smaller than the extent size.)  To be fair, RAID-0 striping won't
> } > accelerate file access for files smaller than the stripe size either.
> } > However, traditionally, raid0 stripe sizes are much much smaller than
> } > LVM extent sizes.  Both are however adjustable.
> } 
> } That sucks. LVM striping really should have a setting where it stripes
> } chunks within a PE.
> } 
> } MfG
> }         Goswin
>
> Why not use this option?

Ignorance. :) I never use raid0 so I never needed to look for all the
stripe parameters.

> -I, --stripesize StripeSize
>     Gives  the  number  of  kilobytes  for  the  granularity  of the
> stripes.  StripeSize must be 2^n (n = 2 to 9) for metadata in LVM1 format.
> For  metadata  in  LVM2  format, the stripe size may be a larger power of 2
> but must not exceed the physical extent size.
>
> I have never use lvcreate with Linux, but have with HP-UX.  Looks about the
> same, but maybe I am confused.
>
> Guy

MfG
        Goswin
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