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Always remember to ask about the "HN Readers Discount".
[1] http://www.rsync.net/products/zfsintro.html
[2] http://arstechnica.com/information-technology/2015/12/rsync-...
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Give your computer ECC memory. Configure ZFS to scrub data regularly. It can be configured to email you of impending (SMART) or actual failure. You can label drives by ID/SN, or if your chassis or controller supports it, it can blink to tell you what drive to replace. It can be configured with a hot spare so the "resilver" starts immediately on failure detection, not "when you happen to fix".
Let me add that you really want to have a hot spare, and if you can't do that (e.g. no extra bay in the chassis), then you should not delay on replacing a failed disk. Have a spare disk on hand, and take the time to replace it ASAP. We lost everything on a FreeNAS system once because we were alerted to a failed-disk error, but decided to wait until the next week to replace it. But then a second disk failed, and we lo…
We buy a batch of 20 drives all at the same time, and they are all the same manufacturer, model, size etc... Possibly even from the same batch or date of manufacture. Then we put them in continuous use in the same room, at the same temperature, in the same chassis. Finally they have an almost identical amount of reads/writes.
Then we act shocked that two drives fail within a short interval of each other :)
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RAID generally does not protect against bit-rot (i.e. undetected errors); it only protects against detectable errors / catastrophic disk failure. ZFS does protect against undetected (at the disk level) errors. To a first approximation, it does this by keeping block checksums alongside pointers so that it can verify that a block has not been changed since it was referenced, by keeping multiple checksummed root blocks,…
> Naturally, there are information-theoretical limits to the number of corruptions that may occur for detection/correction to be guaranteed. To my practical point: Does it tell me, when it approaches that limit or do I have to put in more maintenance? Can it be fixed by swapping one of the drives?
You still need to worry about failing drives and about the integrity of your raidz arrays (or whatever), but that has nothing to do with the flipping bits.
That being said, you can see statistics about error corrections (which should typically be near-zero) and if you see a lot of them it might be advanced warning of a drive dying. But the actual bit errors themselves would not be a problem and you would not need to take any action specifically related to them.
Ooh, these FreeNAS boxes for the home are very nice: https://www.ixsystems.com/freenas-mini/ When I built my home NAS there wasn't an off the shelf FreeNAS option and it was definitely a "research all the things, build your own system" with the huge caveat of "Did you put enough RAM in that?". The 8-bay one is particularly good value, rivalling similar systems by QNAP, and I personally do have a QNAP and if I were to…
One limitation is the 16GB max ram, but given that it's for home use with (presumably) large files and a small number of simultaneous clients, it shouldn't be a problem - even if you use 4x 8 TB disks.
The key is to populate it with ECC ram which should be an absolute requirement for any ZFS system.
I do love FreeNAS, at home and at the office too (for development purposes - I'd trust it for production but with our client base it's better to be more "corporate"). It has a good cross section of features from 'home' to 'pro', AFP/NFS/CIFS/iSCSI, directory integration, plugins (more aimed at home, with things like news downloaders, BT clients).
What do you use instead of zfs in production?
I have bad memories of freenas (before the split/new version) many years ago when I had a disk and power failure... hdb went, so, c/d moved up a letter and it automatically screwed up raid... ... I was able to recover, but, I remember how many hours I spent on it. Please tell me it is better now?
A split caused by Olivier waking up one morning and announcing that freenas is dead because he wants to rewrite 0.8 on Linux because reasons. I switched back across to freebsd right about then as I lost all trust in the project (now NAS4Free).
Currently running FreeNAS for the last 2 years since last machine upgrade.
I've always thought that was essential, it bemuses me that there aren't many solutions out there that help you do this. I guess everyone must buy have loads of disposable income to buy 8 drives at once.
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Your link is people complaining that the source isn't being released fast enough ... and Synology has told them it will be put on SourceForge when they're ready. There seems to be a lot of precedent for that to go how they said it will. There's also an independent community that facilitate installing and using it on your own hardware including the latest version that's still waiting on the source dump.
Sure, no one needs that source code anyway because they are not adding anything of value. But if they are not complying the GPL license they are legally not allowed to use the GPL projects. As an example for their relationship with upstream, they market the btrfs feature ( https://www.synology.com/en-global/dsm/Btrfs ) but don't have anyone working on btrfs (and btrfs could surely need the help). I can see one patch…
Correct me if I'm wrong (please!) but FreeNAS still can't (easily?) do what Synology's 'Hybrid RAID' (basically sharded RAID across drives) facilitates; growing your (redundant, e.g. 1 or more parity drives) volume by adding more drives, and also growing your volume by replacing drives with larger ones. I've always thought that was essential, it bemuses me that there aren't many solutions out there that help you do t…
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Let me add that you really want to have a hot spare, and if you can't do that (e.g. no extra bay in the chassis), then you should not delay on replacing a failed disk. Have a spare disk on hand, and take the time to replace it ASAP. We lost everything on a FreeNAS system once because we were alerted to a failed-disk error, but decided to wait until the next week to replace it. But then a second disk failed, and we lo…
Everyone makes that mistake once. It is an understated problem in building fault tolerant storage arrays. We buy a batch of 20 drives all at the same time, and they are all the same manufacturer, model, size etc... Possibly even from the same batch or date of manufacture. Then we put them in continuous use in the same room, at the same temperature, in the same chassis. Finally they have an almost identical amount of…
Now its 18 disks (3x6 raidz2) from 3 different manufacturers and every vdev has 2 of each. And the vdevs are physically evenly spread throughout the case.
I sleep so much better. It was kind of a miracle the first setup survived the 4.5 years it did.