http://arstechnica.com/apple/reviews/2011/07/mac-os-x-10-7.ars/13

Looks like quasi-logical volume management is in Lion. It does not appear to 
have snapshots. (yet?)

But if you're using Bootcamp (or rEFIt) to support non-Mac OS X operating 
systems, things get even more difficult if you use Core Storage or create a 
Recovery partition due to the limitations of Apple still not supporting UEFI. 
Since no UEFI 2.x support, non-OS X systems must use the CSM BIOS, which only 
understands MBR. And hybrid MBR only support 3 exported partitions from the 
GPT. And hybrid MBRs are just...messy and standards-violating bastardizations.

Being unsure of exactly what you're trying to achieve, it seems like you may be 
better off hosting whatever you're hosting on another platform if you really 
need hours to backup a very large database or something, and need to ensure 
consistency while also keeping the database live. If it's not that big or you 
must have it on OS X, then I think you need a faster way (more read and write 
throughput) to get the data copied while the database is offline, to minimize 
offline time. SAN to SAN copy?

IMO, Apple is clearly exiting enterprise. I think Lion Server is a kind of 
gift. It's almost optional now. Classic was optional at one time and is now 
gone. And Rosetta was optional in Snow Leopard and is now gone in Lion. I don't 
think we're going to see enterprise file system features on OS X except via 
trickle down years later because this is just not an market of interest for 
Apple, thus they aren't innovating in this area.

If what you have is really that considerable of a database, and important, I 
personally wouldn't want it on jhfs+ anyway. It brings nothing to the table to 
ensure data integrity, error detection or correction. It 100% relies on on the 
hardware for this and that's very limited with 512-byte sector drives and 
somewhat less (meaningfully) less limited with 4K sector size (AF) drives.

If you're using xsan, which uses the StorNext file system, maybe there's a way 
it can do snapshots? I would think it might be possible consider the target 
market but haven't found any info to confirm/deny.

Otherwise Solaris or BSD with ZFS snapshots. Or LVM+ext4 which is the RHEL 6 
default and has been used for quite some time for exactly this purpose, so 
there's lots of documentation and support forums for it. It's rather 
straightforward to setup a CentOS 6 server, and add a recent version of 
Netatalk so Macs can see it. You can then use LVM2's snapshot feature and even 
have it mountable over Netatalk (read only if you wish) for performing the 
backup with existing OS X software. Or many other possibilities at that point.


Chris Murphy


On Jul 19, 2011, at 5:03 AM, Richard Taubo wrote:

> Hi!
> 
> Is there an equivalent to a LVM snapshot feature for OS X?
> Just want to make sure that data being backed up are consistent during the 
> run . . .
> 
> Thanks!
> 
> Richard Taubo
> _______________________________________________
> MacOSX-admin mailing list
> [email protected]
> http://www.omnigroup.com/mailman/listinfo/macosx-admin

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