Backup System

[Stupify]

I have some n00b questions in regard with setting up a backup system. Here are few of them that will really help me if you could answer them. To help you understand the scenario I am thinking up here is some details:

Setup will be 4x2TB hard drives on a RAID5 which should be available over the network one way or another (as in NAS or shared from another PC) so that I can read/write to them.

Questions:
1) RAID5 controller addon/mobo integrated - if it fails, a) would I lose all the data, or b) would I be able to take the drives to another system with RAID5 support and access the data, or c) move to another same controller and data is accessible? Any concerns around it?

2) what about RAID enclosures? same set of sub-questions as #1.

3) what about NAS RAID enclosures? same set of sub-questions as #1

4) which of the above would you suggest as best options: RAID5 addon, motherboard integrated, RAID enclosures with eSATA/USB or NAS RAID?

 

[cyberjock]

You should be using RAIDZ and not RAID5.

 

[Stupify]

please educate me.

thx

 

[cyberjock]

RTM...it is that good.

 

[Stupify]

okay i have checked out raidz and it seems to be what i am interested in. it feels similar to raid5 but better.

In that case would you guys suggest me an enclosure that supports multiple hdd - preferably 4 drives sata? i see some raid enclosures - would i be able to use those or not? what "RAID" setting would i set on them? JBOD? I prefer to connect as eSATA.

How do I tie ZFS and FreeNAS?

 

[freshfeesh]

FreeNAS is an operating system that runs on a computer dedicated to FreeNAS. Disc setup (for discs local to that machine), e.g. configuring ZFS, is accomplished through the FreeNAS interface.

 

[cyberjock]

It is not recommended that people use esata or USB for FreeNAS except during initial setup to copy data off of external drives. The issue is that if you have an "accident" and unplug the whole array or several drives are unplugged that share a common power strip you can lose all of your data. The whole premise of FreeNAS and ZFS is reliability. That reliability is compromised significantly if you are using external drives. You're at your own risks/peril if you choose to go that route, and don't say we didn't warn you.

 

[Stupify]

So would I lose all the data even if there was no writes being done to the drives but the system was on and someone disconnects the whole array?

i feel that wouldn't be the case as that would make the FS pretty pathetic - what happens when there is a power outage in middle of a write? external solution shouldn't be any different in that terms.

 

[freshfeesh]

Yep, that's a scary statement that I would like to know the technical reasons for. In the next five years, history says that there will likely be two power outages at my house. My Freenas box will be on. I don't see a technical reason why an internal array on a card would behave any differently than an array in an external enclosure hooked up to an internal card via esata.

 

[cyberjock]

ZFS has checksums and whatnot to help mitigate the risk of losing data when power is lost. While the writes are designed to keep your data safe, issues with using RAID controllers can make this system not work correctly. Some RAID controllers have onboard RAM and the writes are cached. ZFS expects that when it flushes it's cache that the disks really do write the data. Instead some RAID controllers will say the data has been written when it hasn't.

Think about this. If you have 3 power strips and one accidentally gets unplugged you'll naturally want to plug it back in. Of course, there is the risk that you might accidentally unplug a second one. If you want to take the risk, feel free. External stuff will "work" just fine. It's those unexpected oopsies that some people will make. I've seen people accidentally unplug the wrong drive from a RAID5, RAID6, etc. Using external drives just isn't very reliable when you add in the human condition.

There's a reason why high reliability servers use hot swap bays. No way you should EVER be manually plugging in and unplugging hard drives or anything else while the system is running.

Servers should ALWAYS be on an UPS. I know I've seen alot of Windows Servers go tits-up because the file system was corrupted because power was lost. Some RAID controllers offer battery backup devices that provide power to your RAID controller's cache for situations where server power is lost.

As for losing data when there's no writes, you might be okay. But how much of a chance are you willing to take? It's totally your choice. But like I said.. you are at your own risk/peril if you want to do it.

 

[Stupify]

So let me get this clear:

I have a PC with eSATA port which I plan to use to connect an 4 Bay enclosure - Mediasonic HF2-SU3S2. So now if by a chance someone pulls the plug on the enclosure or the esata cable, what would i see happen? So far in Windows world I have seen the impact only to the file(s) that was being written at most. Would I expect anything more on the ZFS or RAIDZ?

 

[praecorloth]

I believe Noobsauce and I were talking in another thread about plugging drives in after they had been unplugged. I had been under the impression that you could unplug a drive from an array and plug it back in, the system (be it FreeNAS or some super expensive enterprise RAID controller) would be able to detect that this was the disk you had in there previously, and merrily carry on with it's business. As it turns out I was incorrect. Whenever you unplug a drive from a RAID and plug it back in, even if it's the same drive, and even if there was nothing wrong with the drive, the array needs to rebuild the data that drive held.

There in lay the danger with removable drives as part of an array. Say you have a RAID 5 or RAIDZ of 3 eSATA disks. If you're working behind the computer for some reason and unplug one, you can plug it back in, but that data needs to be rebuilt. During that time, you are vulnerable to one of the other disks dying and you losing your data. Or if you're working behind your computer and accidentally remove 2 of those plugs. Poof, now your data's gone. (Well, actually there might be some recovery options if you remove the third right away, but those options won't be pleasant, easy, quick, or reliable) And to reiterate, that's just a problem inherent to RAID.

I guess the power outtage scenario might be different. Assuming all of your drives and FreeNAS went down at the same time, you'd probably be alright as far as this issue is concerned. FreeNAS hasn't detected that the drives have been removed from the system, so when it comes up, it doesn't know anything more than an unclean shutdown occurred. But I don't know that for a fact, nor would I want to find out with actual data hanging on the line. There's also different types of power outtages to consider. Maybe you ran out of plug-ins, or are concerned about the draw from one outlet, so you put a couple of those external drives on another outlet. Turns out that second outlet is on a different breaker from the rest of the set up. You fire up a space heater during a cold day in the winter, breaker flips, X number of drives down.

External drives just introduce numerous ways for things to go wrong and you lose your data as a result. These scenarios can all be avoided by keeping your drives internal. Yes, it can be a bit of a pain. Either finding a case with enough bays, or adding a hot-swap bay. But it will be totally worth your extra effort.

 

[cyberjock]

So let me get this clear:

I have a PC with eSATA port which I plan to use to connect an 4 Bay enclosure - Mediasonic HF2-SU3S2. So now if by a chance someone pulls the plug on the enclosure or the esata cable, what would i see happen? So far in Windows world I have seen the impact only to the file(s) that was being written at most. Would I expect anything more on the ZFS or RAIDZ?

It could be nothing, or you could end up with 1 or more corrupt files. There's no way to accurately predict the consequences. If it's midnight and everyone is asleep, you might suffer no data loss at all. It's all about risk mitigation. That's why I've said twice "you are at your own risk/peril...". There's no way to predict what will happen, good or bad. You might have zero problems, or you may suffer serious consequences.

Think of it like this.. If you accidentally put 1/2 gallon of E-85 gasoline in a vehicle not designed for it, then filled the rest of the tank with unleaded gas would you be fine? Your engine may run bad for that one tank but be fine the next time you fill up. It may destroy your engine permanently.

 

[freshfeesh]

That was a very helpful explanation, thanks. It wouldn't have occured to me to worry about RAM on a controller card. I'm using mobo connectors only, so I guess I'm not exposed there. I do plan on getting a UPS, more quickly now that you've made the case. I figured the risk was confined to just a file being written, not the whole enchilada.

 

[praecorloth]

If I may suggest, don't worry about getting a monster UPS. As far as power issues go, the main things someone running a home server generally worries about are:

1. Unclean power.
2. Brownouts. Loss of power just long enough to bring your machines down.
3. Brownouts in quick succession. Especially if your computer is set to return to last state on power failure (I assume this is how most people run their home servers. I know I do. :) ). Power comes back just long enough for the computer to spin up, repeat brownout, server goes down like a Vegas h******. It can't be good for hard drive motors.

You shouldn't have to worry about keeping your NAS up for hours on end. Long enough to survive some brownouts is good. That usually gives you some time to just shut the system down if you're at home and see the lights go off. If you're not at home, chances are you're not going to be home in the amount of time that your UPS will keep your FreeNAS box up anyways, unless you've spent a small fortune on a UPS.

Also, I've heard great things about this site:
http://www.refurbups.com/

I have not used them myself, but I plan to.

 

[Stupify]

noobsauce80, what i am looking on attaching is a single port esata connecting to the 4 bay rack. So its all or none if any disconnect were to happen - similar power outage. What data-loss risks exist now in that setup aside from the general multi-disks failure?

 

[Stephens]

You shouldn't have to worry about keeping your NAS up for hours on end. Long enough to survive some brownouts is good. That usually gives you some time to just shut the system down if you're at home and see the lights go off. If you're not at home, chances are you're not going to be home in the amount of time that your UPS will keep your FreeNAS box up anyways, unless you've spent a small fortune on a UPS.

If you get a UPS compatible with FreeBSD/FreeNAS, it'll shut down in an orderly fashion when the battery gets low (if you set it up correctly). That's the way to do it. I currently have my CyberPower 850PFCLCD set up to shut down my NAS after 30 seconds, though it isn't yet working (configuration issues).

 

[cyberjock]

noobsauce80, what i am looking on attaching is a single port esata connecting to the 4 bay rack. So its all or none if any disconnect were to happen - similar power outage. What data-loss risks exist now in that setup aside from the general multi-disks failure?

I've already answered that as best as I can. I'll quote it again.

It could be nothing, or you could end up with 1 or more corrupt files. There's no way to accurately predict the consequences. If it's midnight and everyone is asleep, you might suffer no data loss at all. It's all about risk mitigation. That's why I've said twice "you are at your own risk/peril...". There's no way to predict what will happen, good or bad. You might have zero problems, or you may suffer serious consequences.

There's a reason why the more senior members always recommend internal.. because quite a few people have been bitten by external and we try to use experience from other members to help prevent loss of data.

I will tell you that if someone told me to build an external array I'd tell them I'm not doing it. I don't want to be the guy they blame when they lose all of their data.

 

[Stupify]

the reason why I am thinking of going with an external enclosure is so that I can securely hide it unlike a full blown case with at least 4 hard drive bays. The security here I am addressing is theft - less likely to go looking for such devices and more likely to just pull all the cables of the computer and run with the case and monitor.

so to elaborate on my grand schema I want to build a backup system that:
1) encrypts the files
2) versions the files (incremental backups taken from client computers or pushed to)
3) data safety from disk failure
4) data safety from physical theft
5) accessible for multimedia/backup purpose over the network

#1, 2 and 5 are more of a software only configuration tasks
#3 can be hardware (raid controller) or software (freenas)
#4 though requires proper considerations. So far my idea with to take a 6ft esata cable to the enclosure and hide + physically lock it down as a theft deterrent and oversight.

if you folks have a better idea let me know - keeping in mind that I want to spend about $200 max setting something like that up aside from the hdd cost.

 

[cyberjock]

I know someone that tried use that logic to protect from theft. Unfortunately the thief was so quick to start yanking cables the hard drive was suspended by it's own cable, then dropped down after it finally unplugged. Hard disk was destroyed.

If you really want to protect it from theft, the best course of action is to back up to another location in my opinion.