Marek.Les@xxxxxxxxxxxxxxx schrieb:
>
> Hello,
>
> >I agree with Simon.
> >
> >When you are talking about a couple of Terabytes, most Raid Arrays
> effectively
> >have their own LVM built in.
>
> First of all, thanks to all for your responses.
>
> Now, the storage solution I am talking about (unfortunately I'm not allowed
> to be specific here, for the moment) is, what you called a high-end one,
> and has some kind of LVM of it's own but from what I understood, it cannot
> simply grow an existing logical volume. It has an internal RAID 5 and I've
> been told that "it could have been done but it's not for the reason of
> security". I can see some point in this, they want to maintain data
> integrity (the way the device works internally is quite complex). So, what
> happens is that when I want to "enlarge" the volume, I get (physically, in
> the OS) a new device, like /dev/sdc. And now I'm on my own to grow a
> filesystem, so I need to use software LVM..
You could still do this by creating a linear array which you could add a
drive. But a) this can not be done while mounted and b) I'm not sure MD
can do this (linear, not raid0) in 2.4 kernels. It was possible with
2.0...
>
> >Generally, software LVM is just needed for 2 features:
> >
> >Snapshots: This is available in many Raid systems, but it can be a fairly
>
> >expensive option, so many people prefer software snapshots. Since XFS
> does not
> >to my knowledge directly support snapshots, one is left to consider a
> software
> >LVM vs. paying for the hardware option.
>
> As you say, this is a fairly expensive option :) But unfortunately, LVM1 is
> deadlocking with xfs_freeze - anyone has any EVMS experience?
Now, do you really need xfs_freeze? You need it for snapshotting but not
for online growing of volumes. If you just want to add physical units to
the volume and then grow the XFS filesystem on it, you can do it while
the volume is mounted and without xfs_freeze!
>
> >Mirroring between Raid Arrays: Some truly paranoid people use LVM to
> mirror 2
> >standalone Raid Arrays to together. This is pretty rare because it is
> very
> >expensive to do. I doubt you are planning on doing this.
>
> Yes, I won't do that.
>
> Marek Les
> Seznam.cz
|