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Re: [Xen-users] Xen with LVM

IDAGroup - R.W.Muller wrote:
Hi Errol

Errol Neal wrote:
Quoting "IDAGroup - R.W.Muller" <robin@xxxxxxxxxxx>:

Hello Errol, I tried that and get a little weird partition table:

sfdisk -l -uS /dev/vms/centos5_data

Disk /dev/vms/centos5_data: 0 cylinders, 0 heads, 0 sectors/track
Warning: The partition table looks like it was made
 for C/H/S=*/255/63 (instead of 0/0/0).
For this listing I'll assume that geometry.
Units = sectors of 512 bytes, counting from 0

  Device Boot    Start       End   #sectors  Id  System
/dev/vms/centos5_data1   *        63   3068414    3068352  83  Linux
/dev/vms/centos5_data2             0         -          0   0  Empty
/dev/vms/centos5_data3             0         -          0   0  Empty
/dev/vms/centos5_data4             0         -          0   0  Empty

I wouldn't worry too much about that. sfdisk is probably just confused. Since the file doesn't have a ioctl, that would be my guess
Ok I just ignore this partitions :)

Now I just have to find out, how I can get ride of the Empty partitions
and how to use snapshot for backup and I'm getting closer
to a usable result :)

lvcreate -L1G -n vmsnap /dev/vms/centos5_data

Then mount it as above. Keep in mind that for snapshots, all changes to the live volume are written to the COW table on the snapshot volume. Make sure you allocate enough space for this.
Ok, that means I need at least douple the hardware space then the size of the LV, or I'm wrong with this? ....let's say my LV centos5 is 80GB in size, will I need a 160GB harddrive in this blade server in order to get the snapshot and then mount and rsync it to another harddrive? ...or what do you recomment
for backup purpose?


You don't need to allocate the double size of your original LV. As Erol said, you have just to allocate enough space to contains all changes made (i.e. writing) on the original partition during the snapshot life. For example if a snapshot is created à 00:00 am and deleted at 03:00 am, and there's no activity on the original LV, you don't need that much space (just to contains syslog writing or things like this). But if there's extensive usage of your original LV you need to allocate more. Writing 600MB (downloading, whatever, ...) of data in your original LV requires snapshots of at least 600MB.

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