Knowledgebase: Filesystem related
Network Filesystems
Posted by Sven Koester on 04 July 2007 16:02
The PresSTORE modules Backup, Archive and Synchronize should not be executed against files residing on network mounted volumes. Instead, a PresSTORE client has to be installed on the host where data is read or written to.

This article describes why.

The AFP (Apple Filing Protocol) is not fully supported, as it lacks support for some important file attributes (ACL's, metadata). In case files are copied over AFP with PresSTORE, such attributes are lost.

When connecting volumes via NFS (Network File System) ot SMB (Server Message Block) protocols to a Mac, data fork and Mac-only related parts (resource fork, finder info, etc) are physically saved as two different files (the AppleDouble format). Currently, files will always remain as two distinct parts in case they are saved/restored/copied with PresSTORE, as the "re-combination" to one single file is not performed. Yet, starting with V3, PresSTORE will automatically assume all non-HFS(+) volumes to be in AppleDouble format and thus perform automatic AppleDouble conversions on-the-fly.

All network file protocols:
If a volume of one host (A) is mounted on another host (B) and the network connection between them fails, the mounted volume on B will no longer be accessible. In case an application, including PresSTORE, is accessing files on that volume, the system call hangs and this causes the calling process to hang, too, maybe forever.

Also, the serving host often does not provide privileged access to the mounting host when mounted with standard options. The PresSTORE server is running as root process, thus on a network volume with standard mount options, file access is mapped to the guest account. This in turn means that PresSTORE most probably has insufficient access rights to save or restore data.

Because of all that, there is a different protocol implemented within PresSTORE, that is the PresSTORE client protocol. This protocol handles all file-access issues properly. Also, in case of a connection failure for any reason, the client is saved up to that point, the missing data is simply handled on to next invocation of the same job, and PresSTORE continues with the next job or the next client.

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Comments (4)
Steve Smulian
26 June 2014 17:56
Explain please how this applies to volumes mounted using tunneling-type protocols like Avid's ISIS and Quantum's StorNext FileSystem Distributed LAN CLient. These do not use the standard AFP/NFS/SMB type protocols and bypass typical TCP/IP protocol issues.
Andre Kuehnemund
07 April 2015 16:50
A mounted volume must be accessible to P5 via standard OS methods. If special client software is required in order to mount a particular remote storage on a P5 server or client, then this remote file system will most likely not be accessible to P5. It is not recommended to use AFP/SMB/NFS mounted volumes for backing up, archiving or synchronizing data. Instead, it is recommended to use iSCSI to mount the remote volume on the server. Another option would be to mount the file system locally on a server, install the P5 software on that server, and configure this server as a P5 client.
Jonah
23 October 2015 21:45
what's the real answer on this. Archiware is currently being sold to us as a product that we can use to archive off Isilon and Avid ISIS. i can't install the client on either of these platforms. Does it work with SMB or not?
Andre Kuehnemund
20 January 2016 14:00
Jonah: The real answer is that if vendors stuck to standard protocols, there would be no problems accessing Isilon or ISIS volume. By going proprietary and 'closed system', EMC and Avid put in hurdles that are somewhat difficult to overcome. One of those being that the P5 software cannot be installed on those systems.

From what I've read, EMC used to support iSCSI their Isilon - but stopped doing so for whatever reason. SMB still appears to be supported.

RE: Avid ISIS
Based on the information I found, Avid does not support iSCSI, but does support SMB sharing.

It appears that with both systems, using SMB/CIFS sharing will be your only option. Alternatively, there are more open systems like Ardis DDP or Facilis Terrablock (just to name a couple, not an endorsement) that work just fine with P5.
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