Re: [ADMIN] The OS Command for pg_hotbackup -- Use lvmsnapshot instead of tar cvzf

On Tue, Mar 2, 2010 at 12:20 PM, Scott Marlowe <scott.marlowe@gmail.com> wrote:
> On Tue, Mar 2, 2010 at 8:43 AM, Arnold, Sandra <ArnoldS@osti.gov> wrote:
>> I am currently using the pg_hotbackup Perl script to backup my production
>> PostgreSQL database.  However, the next production database is going to be
>> close to a terrabyte in size.  We feel that a tar cvzf command is not the
>> correct OS backup solution to use.  Instead we would like to use
>> lvmsnapshot.  Is anyone using the pg_hotbackup script but instead of the tar
>> cvzf OS command are they using lvmsnapshot?
>>
>> Or, is anyone using lvmsnapshot and doing point-in-time recoveries?
>
> I do not run my databases on LVM because, at least in the past, LVM
> did not properly honor fsync / write barrier commands.  I don't know
> if this has since  been fixed.   If your transaction rate on LVM is
> unnaturally higher than it should / could be, then suspect it is not
> fsyncing, and putting your data on it is putting it at risk.

From what I've read further on, it seems it's ok as long as it's on a
storage system like a battery backed RAID controller.  Still, someone
on the list did some testing and LVM resulted in a reduced throughput
when on large fast RAID arrays, so do some testing before you set off
into production with LVM.