----- "Rob Kampen" <rkampen@xxxxxxxxxxxxxxxxx> escreveu:
> De: "Rob Kampen" <rkampen@xxxxxxxxxxxxxxxxx>
> Para: "CentOS mailing list" <centos@xxxxxxxxxx>
> Enviadas: Quinta-feira, 26 de Setembro de 2013 17:11:06 (GMT-0300) Auto-Detected
> Assunto: Re: to lvm or not to lvm - why/when to use lvm
>
> On 09/26/2013 09:35 PM, James A. Peltier wrote:
> > ----- Original Message -----
> > | ----- Original Message -----
> > | | Hi,
> > | |
> > | | I was wondering, why/when it is useful or when should I avoid
> to
> > | | use
> > | | LVM.
> > | |
> > | | I think the big advantage of LVMing is if you modify (rezising,
> > | | ...)
> > | | disk and filesystem layouts "a lot".
> > | |
> > | | Are there any real pros or cons for following situations
> regarding
> > | | e.g.
> > | | management and speed?
> > |
> > | The speed at which you can manage your disk environment through
> the
> > | use of LVM makes most of the tradeoffs worth while. Of course,
> YMMV
> > | so you're best to test.
> > |
> > | | e.g.:
> > | |
> > | | I do have a server system raid for which the disk layout will
> not
> > | | change; e.g. /var /usr /home will not change much in size.
> > |
> > | This isn't so much the issue. What if *any* partition
> requirements
> > | *do* change in the future. LVM can account for that my allowing
> you
> > | flexibility to make a change should it be required. Standard
> > | partitioning is less flexible in this regard.
> > |
> > | | OR
> > | |
> > | | I do have some file storage shares (iscsi raids) up to some TB
> each
> > | | on
> > | | one big storage device.
> > | |
> > | | Sometimes (e.g. after a server crash) it is useful to remount
> the
> > | | storage to a different server.
> > |
> > | Standard caveats apply. If the Volume Groups or the Logical
> Volumes
> > | are named the same moving them to another system with similar VGs
> or
> > | LVs can be problematic. Same goes for file system labels, albeit
> > | both are relatively easy to fix in such a scenario.
> > |
> > | | Should I use LVM on the iscsi storage volumes?
> > |
> > | I would find it difficult to find a case where LVM shouldn't be
> used
> > | because of it's flexibility. I tend to use full disk LVM (no
> > | partitions at all) and file system labels for mounting and the
> like
> > | (labels match LVs).
> > |
> > | lvcreate -L 20G -n csgrad DATA
> > | mkfs.xfs -L csgrad /dev/DATA/csgrad
> > |
> > | /etc/fstab
> > | ----------
> > |
> > | LABEL=csgrad /exports/csgrad xfs defaults 0 0
> > |
> > |
> > | LVM offers other additional flexibility too in that you can
> migrate
> > | PVs from one device to another online. So if you have one iSCSI
> > | server that is coming off support and you are replacing it with
> > | another, you can use pvmove to move the data from one target to
> > | another.
> >
> > Oh! One last case in point. Partition Alignment. This is very
> important to the performance of a disk subsystem. With full disk LVM
> it's not an issue at all.
> >
> Not having much experience with LVM, I just wondered how this last
> comment applies.
> Surely the alignment of partitions has got to do with the underlying
> hardware and how it seeks to and finds the beginning of where it wants
>
> to read - the sector. I am curious how LVM negates this hardware
> constraint.
>
Well, I think this is one of the big examples of what
we can do with LVM: http://www.greyoak.com/lvmdrive.html
--
Antonio da Silva Martins Jr.
Analista de Suporte
NPD - Núcleo de Processamento de Dados
UEM - Universidade Estadual de Maringá
email: asmartins@xxxxxx
fone: +55 (44) 3011-4015 / 3011-4411
inoc-dba: 263076*100
"Real Programmers don’t need comments — the code is obvious."
--
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