Well, I have a similar problem/desire.
I want to have RAID5 for redundancy/reliability. But I want to be able to
resize the file system stored on the RAID5 array, as well as being able to
add and remove hard disks to either increase/decrease available storage.
What would be your recommendation for a configuration?
At the moment, I'm considering using EVMS with its RAID5 regions, and put
LVM2 on top of it.
Thanks in advance,
Erik.
> -----Original Message-----
> From: linux-lvm-bounces@redhat.com
> [mailto:linux-lvm-bounces@redhat.com] On Behalf Of Sam Vilain
> Sent: Monday, February 28, 2005 12:11 AM
> To: LVM general discussion and development
> Subject: Re: lvm over raid5 - sizes
>
>
> Scott Serr wrote:
> > I have alot of ideas going through my head. Here is my situation:
> >
> > I've had 5 IDEs with 4 partitions each. Each partition is
> in a RAID5
> > md:stripped.
> > md0 = hda5, hdb5, hdc5, hdd5, hde5
> > md1 = hda6, hdb6, hdc6, hdd6, hde6
> > md2 = hda7, hdb7, hdc7, hdd7
> > md3 = hda8, hdb8, hdc8, hdd8
> >
> > md0-3 are in an LVM2 volume group. This makes it really nice when
> > expanding or adding another disk because I just pull say
> md3 out of the
> > volume group... rebuild md3 bigger and then add it back.
> > I just upgraded, replacing hde with a bigger disk and while
> the pvmoves
> > are taking FOREVER... I thought what is the right size for
> the RAID5
> > chunk-size?
> >
> > I have chunk-size = 128k right now.
> >
> > The pv extents size is (always?) 4MB.
> >
> > Am I just shooting myself in the foot by not making my RAID
> chunk size
> > atleast 1MB? Can someone give me a reason to increase it?
>
>
> You're shooting yourself in the foot with RAID 5 and a crazy
> setup like this in the first place. I sure hope this isn't
> for a production box :)
>
> Just get more disks and use RAID 1. It's faster, simpler,
> and more robust. You can still do all of the tricks that
> you're looking for.
>
> Hey, maybe one of the disks has failed. Standard RAID 5
> behaviour as designed in this case is to slow to a crawl.
> Alternatively maybe you're just experiencing what is known in
> the 'biz as "The Butterfly Effect".
>
> With most striping, keep the chunk size as large as possible.
> It's a real waste to spend 10ms waiting for the disk platter
> to rotate, and then only read 128kB of data. Set it as high
> as possible.
> --
> Sam Vilain, sam /\T vilain |><>T net, PGP key ID: 0x05B52F13
> (include my PGP key ID in personal replies to avoid spam filtering)
>
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