Spanning a volume over a network or with a remote device

Storm89161 wrote:

Or what if I used NFS on the storage system and tried mounting that to the server and concatting that?

This is effectively one of the two options I previously suggested to you, that is to 're-share' via a single server multiple other servers so as to provide a single point of entry to clients.

The other option as a reminder since it is now several messages ago, is to use Microsoft's DFS (Distributed File System) which is specifically designed to merge multiple file servers in to one system and is supported by Mac clients but not Mac servers.

I think you should stop trying to flog a dead horse and look at these two options or give up.

There's no difference between striping (RAID-0) and spanned volumes, in terms of access. Lose one disk or lose one server in RAID-0 or in some sort of spanned set, and you have a very large hole in your virtual disk. (There are performance differences here between RAID-0 striping and concatenated volumes, though the presence of a glacial-compared-to-a-storage-bus gigabit Ethernet network link will likely make that difference irrelevant. Served volumes — host-served or NAS-served — are very slow, compared with most any disk I/O bus.)

You can use mount points in OS X to bring other volumes online via NFS or SMB/CIFS or AFP. This may be what you are thinking about, with your references to spanning. This is what OS X calls a "share" and involves a host running some software to serve a storage volume, and requires coordination in the file server to avoid collisions — that's part of NFS, SMB/CIFS and AFP servers, though file-level sharing is not AFAIK supported by any of these — and it's what I've been suggesting. NAS software provides these services, and are available as discussed previously.

If you want reliability, that's RAID-1 or better. Not RAID-0, nor mount points and shares, nor whatever you're referring to here as spanning. (Which outside of one rather weird operating system and its so-called bound volume sets, I've not encountered anything similar. RAID-0 striping is the closest analog, and that is almost always either host- or controller-specific. Not multi-host.

I know of no spanning software that will do what you want, other than what I've mentioned above and in previous replies.

Configure the spare box(es) as a NAS using previously-mentioned software or similar, create the exports on the NAS box, mount the disks as mount points, etc.

Storm89161 wrote:

I recall you saying to mount it to a combined volume. I mean including that server in the combined volume.

Yes and I believe this may be possible. Something like the following.

/ = root of 'master' server

/Users/Shared = a shared folder on the master server shared via AFP

/Users/Shared/server2 = an NFS mount of a second server

In theory if a client user logins in say via AFP to the shared folder, they could browse down in to the sub-folders including of the other servers. These NFS mounts are being 're-shared' by the AFP share point.

You could pick any folder as the top-level instead of /Users/Shared for example you could use an external data volume on the master server. All you need to do is create NFS mounts inside it.

Storm89161 wrote:

I recall you saying to mount it to a combined volume. I mean including that server in the combined volume.

Please let us know what you find here; that can do that.

Storm89161 wrote:

Is there a way through raid that would give the same effect?

That's already been discussed.

I've always been iffy towards afp and smb but that just might be my stubbornness talking.

If you think a file share is iffy in this context, then you'll find that RAID configurations with virtual volumes that can be built from physical volumes on multiple hosts will be quite rare. Also very difficult to get working correctly — the one bunch I'm aware of that has managed this took ~twenty years of experience and fixes and a ground-up rewrite to get it all working, and that support is OS-integrated and not available for OS X.

Please go do some research on available options and requirements. Let us know what you find.

I too would like to forward my name to this class.

John Lockwood's suggestion about the 'daisychain sharing' is very interesting. Surely going to take some spare units and storage to try and set it up on it's own subnet to see what the results are in terms of reliability figures, bandwidth and speed. Unfortunatly only SATA II devices spare, but that will have to do.

Leo