Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

FreeNAS: Open Source Storage Operating System

freenas.org

Post reply on HN
Print view View original

31–40 of 182 posts

Re: FreeNAS: Open Source Storage Operating System

#31

Post by zwerdlds »

jzelinskie wrote: post #21
tracker1 wrote: post #8

Although I don't think I'd ever DIY another NAS box, I would suggest the following, use a common chipset controller that exposes each drive/device separately with all information, some don't. Also, prefer a system with ECC, Asus supports ECC on most AMD FX supporting motherboards for the less expensive option there. Also, have 2 spare drives on hand. I went back to Synology after my uper-nas crashed and burned (reall…

I wanted to do something like this, but after reading about the failure rates of drives and raid, once one disk fails, it seems like you're fucked. Anybody got some stories or numbers that prove that while repairing my raid for one disk failure I won't just destroy the rest of my drives?

I've got a FreeNAS box which has endured two disk failures no problem. I have scheduled weekly rebuilds which I'm hoping finds bad blocks ahead of a failure-base rebuild.

Re: FreeNAS: Open Source Storage Operating System

#32

Post by allendoerfer »

Storage is a really weak area of mine, but it is important, and I do not see much technical discussion here anyway, so I am going to expose myself:

How does integrity protection work in practice? I know that the bits on the HDD itself do not map one to one to bits you can actually use and that it uses that to protect us from flipped bits.

I know that beyond that RAID/RAIDZ is supposed to help. I guess redundancy alone does not help. Two copies would not help to determine which bit is the correct one, you would need three. Once you have these, I guess you would be able to detect corruption. Am I guessing correct that duplication beyond 3 times would just help with read speed and in the case when a drive fails while one is already dead (e.g. when you are rebuilding)?

What then? Does RAID/ZFS automatically fix it? I imagine at some point the drive would have to be replaced, do you have to check that manually or does it detect that by itself? I imagine after that you would have to run a rebuild.

So I guess my question would be: Could I put a FreeNas in a corner a room and leave it there? Would it just blink when I need to put a new drive in or would it need more maintenance? Of course talking about worst case scenarios here, so say I want this to live for 10 years sitting in the corner.

Re: FreeNAS: Open Source Storage Operating System

#33

Post by evv555 »

tracker1 wrote: post #8

Although I don't think I'd ever DIY another NAS box, I would suggest the following, use a common chipset controller that exposes each drive/device separately with all information, some don't. Also, prefer a system with ECC, Asus supports ECC on most AMD FX supporting motherboards for the less expensive option there. Also, have 2 spare drives on hand. I went back to Synology after my uper-nas crashed and burned (reall…

If you have a way to deal with the noise then getting a 2nd gen rack server off ebay is a good way to go. At the least you'll get more ram and hard drive bays for your money.

Re: FreeNAS: Open Source Storage Operating System

#34

Post by ultramancool »

goda90 wrote: post #30
ultramancool wrote: post #11

Earlier quoted context omitted.

Those 3TB Seagate drives are literally the worst in the business. The 2TB and 4TB are pretty good (roughly on par or better than competitors according to the backblaze reports) but those 3TB drives were utter shit for some reason, ~20% year over year failure rates. Some retailers have even started to sell the 3TB Seagate drives at almost the same price as the 2TB ones. Probably the only way to get rid of them.

Well that's reassuring... I just built my home NAS. 3 3TB WD Reds and 3 3TB Seagate NAS drives. Two of the Seagates were DOA so I got them replaced. I ran full hard drive tests on them without problems but now I'm extra paranoid.

That's what RAID is for, just make sure you scrub it often enough to catch any potential failure. If you're ever looking for replacements, those 4 TB Seagates are hard to beat without paying enterprise-level prices, despite how much of a turn-off the high failure rate on their 3TB drives may be.

Re: FreeNAS: Open Source Storage Operating System

#35

Post by codemac »

allendoerfer wrote: post #32

Storage is a really weak area of mine, but it is important, and I do not see much technical discussion here anyway, so I am going to expose myself: How does integrity protection work in practice? I know that the bits on the HDD itself do not map one to one to bits you can actually use and that it uses that to protect us from flipped bits. I know that beyond that RAID/RAIDZ is supposed to help. I guess redundancy alon…

> Two copies would not help to determine which bit is the correct one, you would need three. Once you have these, I guess you would be able to detect corruption. Am I guessing correct that duplication beyond 3 times would just help with read speed and in the case when a drive fails while one is already dead (e.g. when you are rebuilding)?

You're confusing two topics. Integrity vs. availability. 3x copies, RAID4 XOR, RAIDZ (a form of RAID6), etc are about increasing the availability of your data in the face of device failure/partitions.

The integrity of you data is computed different ways in different systems, but you can safely think of it in your head as a pile of checksums on top of eachother. There is a half decent blog entry[0] on Oracle's website, but you can mentally model it as having checksum on disk for each block, which then is combined with other blocks into some larger object that is also checksummed, and on and on until you have "end-to-end integrity". It is a feature of all serious storage systems.

I'd love if someone who was more familiar with ZFS could respond with how ZFS's internals work for you.. I worked at a direct competitor of Sun's that sued eachother over this stuff, so I actively tried to not learn about ZFS. I regret this.

[0]: https://blogs.oracle.com/bonwick/entry/zfs_end_to_end_data

Re: FreeNAS: Open Source Storage Operating System

#36

Post by Nacraile »

allendoerfer wrote: post #32

Storage is a really weak area of mine, but it is important, and I do not see much technical discussion here anyway, so I am going to expose myself: How does integrity protection work in practice? I know that the bits on the HDD itself do not map one to one to bits you can actually use and that it uses that to protect us from flipped bits. I know that beyond that RAID/RAIDZ is supposed to help. I guess redundancy alon…

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, and by having enough redundancy to reconstruct blocks that fail their checksums. Naturally, there are information-theoretical limits to the number of corruptions that may occur for detection/correction to be guaranteed.

You should refer to the relevant wikipedia pages if you want more detail than that :p

edit: To answer your actual question, yes, you should be able to leave a ZFS box in the corner unattended for years with reasonable confidence that your data is safe and uncorrupted (tune redundancy settings to your taste on the space efficiency vs. error tolerance trade-off). Two caveats: 1) the machine must have an effective means of communicating a catastrophic disk failure for you to resolve (this should hold for any made-for-purpose NAS device, but you'll need to do some work if you're DIY). 2) ZFS does not actively patrol for corruptions, it fixes problems when it encounters them. If your data is not being periodically accessed, there will need to be some provision for walking the filesystem and correcting any accumulated errors (the ZFS scrub util exists for this purpose, but it has to be used)

Re: FreeNAS: Open Source Storage Operating System

#37

Post by tobias3 »

benologist wrote: post #28
tobias3 wrote: post #22

Earlier quoted context omitted.

This looks just like their GPL source drop location. No build instructions, no readme etc. This thread seems to confirm this notion: https://forum.synology.com/enu/viewtopic.php?t=120535 Here is the one for Thecus: http://www.thecus.com/Downloads/GPL/ QNAP: https://sourceforge.net/projects/qosgpl/ And since they haven't published the latest versions they are in violation of the GPL.

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 set from them which hasn't made it into mainline ( https://patchwork.kernel.org/project/linux-btrfs/list/?submi... ).

Re: FreeNAS: Open Source Storage Operating System

#38

Post by [deleted] »

tobias3 wrote: post #37
benologist wrote: post #28

Earlier quoted context omitted.

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…

[deleted]

Re: FreeNAS: Open Source Storage Operating System

#39

Post by allendoerfer »

Nacraile wrote: post #36
allendoerfer wrote: post #32

Storage is a really weak area of mine, but it is important, and I do not see much technical discussion here anyway, so I am going to expose myself: How does integrity protection work in practice? I know that the bits on the HDD itself do not map one to one to bits you can actually use and that it uses that to protect us from flipped bits. I know that beyond that RAID/RAIDZ is supposed to help. I guess redundancy alon…

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?

Re: FreeNAS: Open Source Storage Operating System

#40

Post by FireBeyond »

allendoerfer wrote: post #32

Storage is a really weak area of mine, but it is important, and I do not see much technical discussion here anyway, so I am going to expose myself: How does integrity protection work in practice? I know that the bits on the HDD itself do not map one to one to bits you can actually use and that it uses that to protect us from flipped bits. I know that beyond that RAID/RAIDZ is supposed to help. I guess redundancy alon…

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".

Post reply on HN