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Hugh

New to iSCSI.... Attaching to multiple machines

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Hi all,

I'm kinda new to iSCSI - so I don't know what's possibly and what's not, and I've possibly made some wrong assumptions.

I'm working at a small setup with 3 other people, and we were after a good RAID-5 setup that would happily sit on the network and not need a machine to host it.

I was under the (possibly mistaken) impression that this would be fine with iSCSI.

I'm discovering today, though, that setting up an iSCSI connection on one machine to the drive is absolutely fine, but as soon as I look at the drive on another connected machine, it corrupts the file system.

Is there a way to do this? I'm after the best possible performance (obviously).... I'm thinking that I'm going to just have to revert to using it without iSCSI... I'd love to hear any thoughts on this one.

Thanks!

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Hi,

yes, all local filesystems like HFS and UFS are only to be used by one computer at a time since, as you have already noticed, get instantly corrupted if you access the same volume from more than one Macs simulatneously.

To be able to use one volume on multiple computers, you'd need what is called a Clustered Filesystem. Apple's own one is Xsan (ACFS). The major drawback of Xsan are the follwoing issues:

- it's quite expensive

- you'll need one ore two so called Metadata Controllers (okay, those can act as normal workstations on your network as well, and as your setup is quite small, you'll probably don't even recognize that)

- handling Xsan can sometimes be a real pain, if anything goes wrong - I knowing this from my own Xsan network, that I am running on our campus network, but we do it over FibreChannel, so there more pieces thrown into the puzzle here

If you need shared storage on the same volume than iSCSI is not for you. I am using it to host big RAID systems and have them connected to my Xserves, while being able to switch these volume to another server, if needed. Plus, running iSCSI volumes from something like OpenFiler gives you the possibility to utilize the underlying LVM (Logical Volume Management), but that is likely out of scope for you either.

For a small network, if you want only little administrative overhead, I'd suggest to got for one of the NAS devices, or to build one using Linux.

Cheers,

budy

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Thanks budy - that's good to know.

I've got a Thecus N5200 Pro - I'll get it set up to just do it all as normal rather than using iSCSI. It's a bit of a bugger, but hey, it's better than using the mirrored FW400 drives that we're running off at the moment!

We don't have the budget for a system like the one you described (at the moment)

Anyway, thanks for clearing that all up for me. It's good to know what I was missing.

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You're welcome! ;)

I am also using a N5200Pro and I am running 3 iSCSI drives on it, but they're all connected to different Macs in my house, so I have no problem there.

The N5200Pro is a pretty decent NAS unit and after some struggling with it, I really can recommend it for SOHO use.

Cheers,

budy

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Hi,

yes, all local filesystems like HFS and UFS are only to be used by one computer at a time since, as you have already noticed, get instantly corrupted if you access the same volume from more than one Macs simulatneously.

To be able to use one volume on multiple computers, you'd need what is called a Clustered Filesystem. Apple's own one is Xsan (ACFS). The major drawback of Xsan are the follwoing issues:

- it's quite expensive

- you'll need one ore two so called Metadata Controllers (okay, those can act as normal workstations on your network as well, and as your setup is quite small, you'll probably don't even recognize that)

- handling Xsan can sometimes be a real pain, if anything goes wrong - I knowing this from my own Xsan network, that I am running on our campus network, but we do it over FibreChannel, so there more pieces thrown into the puzzle here

If you need shared storage on the same volume than iSCSI is not for you. I am using it to host big RAID systems and have them connected to my Xserves, while being able to switch these volume to another server, if needed. Plus, running iSCSI volumes from something like OpenFiler gives you the possibility to utilize the underlying LVM (Logical Volume Management), but that is likely out of scope for you either.

For a small network, if you want only little administrative overhead, I'd suggest to got for one of the NAS devices, or to build one using Linux.

Cheers,

budy

Studio Network Solutions sells SANmp, which is an alternative to Xsan. Odd you didn't mention it since this is their forum.

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Studio Network Solutions sells SANmp, which is an alternative to Xsan. Odd you didn't mention it since this is their forum.

Well, that's simply because I don't know this product. I don't use it and thus I can't recommend it or not recommend it.

And… since sns provides the globalSAN initiator free of charge and this forum is the only place where you might get some help, I don't see the point in having to promote their other products when trying to help o ut other forum members.

Cheers,

budy

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