Best practices for OOX with external hard drives

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Best practices for OOX with external hard drives

Postby zxcvb » Tue Sep 29, 2015 4:18 pm

Hi,

I would like to know the best practices for openzfs with external hard drives in OSX.
I'm using latest (1.4.2) binaries with 3 external hard drives (USB3.0) in a macbook pro (Yosemite).

The problem is classic...at the end of the day I need to take the laptop home and need to unmount all disks by "hand". This include closing all terminals or softwares that are reading or lying in some directories inside this pool (tank0). Yesterday I completely forgot to do that and (don't know if was the cause) I got it metadata corruption. It doesn't look like i lost anything since the pool is very new and i was still sending some data to it ( for the sake of safety, i just recreate everything and start rsync again to the pool).

I saw some really improvements with the last verison (with external hard drives in other versions things were not transparent when we shifted the order of the drives), but I'm still concerned about the reliability of openzfs with such removable drives.

So there is any option or practice to avoid this type of corruptions or how to handle zfs with external storages?

Cheers
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Re: Best practices for OOX with external hard drives

Postby lundman » Tue Sep 29, 2015 5:53 pm

Exporting before unplugging is obviously desirable, but one of the better features with ZFS is that if you do forget to do that, it can at least tell you if a file (or, its metadata) is bad. With HFS, you would simply not know until you tried to use it.

In this case, metadata is stored twice. It is likely that had you run scrub on the pool, it would have fixed itself, or at the very least, told you exactly what file was being partially written when you pulled the plug on it.

Now it sounds like you have 3 HDDs that are each single pool(s), this is obviously less redundant and there is nothing ZFS (or any filesystem) can do. Normally, the 3 HDDs would be set up in a redundant fashion adding even more protection from user-caused-issues like this.
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Re: Best practices for OOX with external hard drives

Postby mjt5282 » Fri Oct 02, 2015 12:24 pm

i used to run ZFS on my Mac Pro with external ESATA cables in a 4-disk enclosure(s). I had worked for a long time to find ESATA cards that worked with Mac OS X and didn't need special drivers and had compatibility with reliable enclosures. I found that I was happier with a NAS solution instead of my Mac but if you'd like a recommendation for a Mac Pro solution I can give you one. Alternatively, there is a thunderbolt solution using enclosures and a thunderbolt adapter/enclosure that can house PCI cards , but it is kind of expensive. Usually, this solution is used when software is required to read and write large files (graphics or video perhaps) and NAS is too slow.

I would suggest zpool export (name of pool) before powering down ZFS disks and computer prior to relocating them to another machine or location.
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