At 1:40 AM +0200 10/9/2011, t...@nehaia.dk wrote:
lacie back up drive with 3 firewire ports on the back
[snip]
wondering if I could just hook those two up to the drive as well?
No.
Multiple computer devices on an i/o bus (scsi, firewire, usb, etc),
are not supported by OS X or the HFS+ file system.
While things might seem to work if you've only got the device mounted
on one computer at a time, there will be trouble. When the OS does a
bus scan -- either at boot or wake or triggered (by seeing a drive
spin up) or periodic, it will suddenly see the drive and try to mount
the volumes. Then you'll have things mounted r/w from multiple
computer with NO coordination between them. It WILL corrupt both the
files systems and data. Note please that mounting the volumes r/w
from one computer and r/o from the others is NOT a solution either -
as there are still parts of the file system accessed r/w.
Apple had a choice: Develop a distributed file system (difficult) or
keep a single point of access (no brainer). They choose the latter.
The "official" way to connect a drive (volume) to multiple computers
is to use a NAS box (an intelligent drive that hangs off your LAN) or
with sharing (a drive that connects to a single computer and that
computer coordinates all access across your LAN).
At 5:19 PM -0700 10/8/2011, peterh...@cruzio.com wrote:
The IBM System/360 and its follow-ons could attach a single drive to
up to eight independent CPUs, but this was supported by special
software within each OS and with special commands within the drives.
Basically, one processor would issue a "reserve" command to the
drive, thereby preventing any other processor from accessing that
drive. [etc]
Digital did a full file system distribution in VAX/VMS, back in the
mid-80s. They took IBM's techniques and distributed 'em even further
as part of their VAXcluster concept. Full r/w access across multiple
CPUs, with automagic failover and recovery mechanisms. Initially the
CPUs had to be tied together with DEC's fast Computer Interconnect
(CI) bus (dual 70 Mbps star), but later via normal ethernet. Locking
was done at the record, block, and file level. Very cool. Very
disappointing that this type of high reliability file system went the
way of the dodo, except for enterprise Unix solutions. It's
something that I think OS X should have had built-in since 10.1.
sigh. Defeat from the jaws of victory. sigh.
At 5:59 PM +0200 10/9/2011, t...@nehaia.dk wrote:
what other ways to use the same back up drive for two puters exists then?
CarbonCopyCloner will back up to afp shared volumes, be they NAS or
on another computer.
At 5:31 PM +0100 10/9/2011, Bruce Ryan wrote:
would partitioning the firewire drive work? Then mount only
partition1 on mac1 and partition2 on mac2.
No. The partition map itself would be clobbered. HFS does NOT
support that type of distribution. (see above).
The way I do it here is to have a NAS attached to my network, with
usernames for each potential user and shares for each mac we back up.
[snip]
The LaCie isn't a speed-demon
Yea, well, that's a basic limitation of a NAS box. Unless you've
coughed the Big Bucks for multiple 10 Gbps NICs, your LAN is limited.
100 Mbps to 1 Gbps is a far far cry from SATA speeds (up to 6 Gbps).
Shouldn't really matter tho -- backups are usually a background
operation. Who cares how fast they run?! :)
FWIW,
- Dan.
--
- Psychoceramic Emeritus; South Jersey, USA, Earth.
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