----- "Rob Kampen" <rkampen at kampensonline.com> escreveu: > De: "Rob Kampen" <rkampen at kampensonline.com> > Para: "CentOS mailing list" <centos at centos.org> > Enviadas: Quinta-feira, 26 de Setembro de 2013 17:11:06 (GMT-0300) Auto-Detected > Assunto: Re: [CentOS] 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 at uem.br fone: +55 (44) 3011-4015 / 3011-4411 inoc-dba: 263076*100 "Real Programmers don’t need comments — the code is obvious." -- Esta mensagem foi verificada pelo sistema de antivirus e acredita-se estar livre de perigo.