9.2 Zvol for iSCSI...how to populate

[marcevan]

I think I'm missing something and the guides aren't helping me much.

I have a pool with all datasets and broken out into basic media datasets like movies, television, music, photos, home video.

That's all populated with data.

I want to try iSCSI and managed to get it going but I have to use a zvol. So is there any way to make a zvol already have the dataset data? I always have to format the disk on my windows side but I'm just not clear on the purpose of zvols in lieu of say CIFs for getting access to freeNAS data.

 

[jgreco]

There are two major classes of network storage.

One is NAS. This is where your PC (or PC's) send high level requests for files over the network to your filer, which then accesses files on a filesystem that it maintains, like ZFS.

The other is SAN. This is where your PC (NOT multiple PC's) sends low level requests for disk blocks over the network. Your PC pretends that this is a local disk and makes one of its own filesystems on top of that. So you format your iSCSI volume as NTFS or something like that.

Now this is where people go awry! There are two common mistakes:

1) You are using ZFS exclusively to store blocks. ZFS stores no individual files and does not understand NTFS, but can store the NTFS blocks perfectly regardless. Your FreeNAS system cannot put files onto the volume because it does not know NTFS. Your FreeNAS system cannot retrieve files from the volume because it does not know NTFS. But your PC does know NTFS, so you can use your PC to do those things.

2) It is very common for people to think that they can share the iSCSI volume. FreeNAS will not prevent you from doing this, because some file systems are what we call "cluster-aware," meaning it is safe for a cluster of machines to all mount a shared hard drive. NO FILESYSTEM YOU ARE LIKELY TO BE USING IS CLUSTER-AWARE. So mounting the same iSCSI volume on two Windows boxes will lead to data destruction. Don't try it.

In my opinion most people do not have any business messing with iSCSI until they can rationally explain why that statement is wrong.

 

[enemy85]

1) You are using ZFS exclusively to store blocks. ZFS stores no individual files and does not understand NTFS, but can store the NTFS blocks perfectly regardless. Your FreeNAS system cannot put files onto the volume because it does not know NTFS. Your FreeNAS system cannot retrieve files from the volume because it does not know NTFS. But your PC does know NTFS, so you can use your PC to do those things.

I use an ISCSI device extent as backup destination of my PC.
I know there is no way to access these files from the NAS itself but just from the pc where the ISCSI hard disk is mapped.

my question is:
considering i had to NTFS format the zvol/iscsi hd from the pc the first time i created it, in case i need to access that ISCSI hd from another pc, NOT AT THE SAME TIME, but just to recover files in case of emergency, would it be possible or am I obliged every time to format again the volume so my backup plan is useless?

Thanks

 

[jgreco]

Yes, from that point of view it is like a external USB or external SATA HDD.

 

[enemy85]

Yes, from that point of view it is like a external USB or external SATA HDD.

that's the way i thought it worked and how i designed my "backup plan", so good to know u confirm my idea is functional!
thank you!

 

[marcevan]

Hmm... good explanation 'ol grinch.

Well, never found the need to backup to freeNAS since my HTPC has nothing to backup. All the data is actually on freeNAS in datasets.

Thanks for the info and now it's time to remove all the iSCSI and zvols.

 

[jgreco]

That sounds like the best plan...

 

[mcolinp]

Is there a way to use a Jail to make Windows be able to read/write at the system level? I am asking this here, because ISCSI was about the closest solution I could find so far. After reading up on all the potential pitfalls; I am not really liking it as a solution to my needs. The issue I am trying to resolve, is that I install a large number of CAD programs; each with its own "Content Library" which take up way too much space to host on a local client machine. (-Especially when I run only a single SSD drive for the OS.) The trick, is getting the program(s) to think that a network location is a valid path. I already tried creating a "Library" with a symbolic link; which still did not work. I am open to any suggestions . . .

-EDIT- I should clarify that an additional issue is that I would like the hosted "Content Centers" to be usable by multiple users; (not immediately; but eventually).