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How safe would you feel with a Raid 5 array?

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I'm perfectly content running my home system on a 4 disk RAID5 system (P5B Deluxe MB). I use the Seagate ES series drives (320MB each) and I love it. I do occasionally make a backup of the critical "stuff" to my home server as a CYA. Of course, I'm also not THAT worried about loosing everything.

Work was different story. There, we run a NetApp dual headed F880 with over 9GB of storage across 100+ drives. Everything on there is redundant. It also sits on an online power supply (batteries power the system 100% of the time, no switch over delay) and there is a pair of diesel generators on standby. Needless to say, that system also has a very robust tape backup schedule (with off site archive) along with continuous virus scanning. It would take close to an act of God to cause permanent data loss. And yes, the data being generated IS worth that kind of protection.

My system is only one of about thirty NetApp systems at my site alone. And it is one of the smaller ones to boot.
 
well.make sure you can get a replacement card..or have one on standby.
have a drive on standby as well for quick replacement.
other than that, its pretty safe😛 raid 6 is what you want... or raid 5 with installed spare with automatic restore on failure... it probably exists.

anyways, going above and beyond for your pr0n collection? 🙂😉:heart:
 
Even RAID1 can't protect against filesystem corruption. I'd only feel safe enough to do one array-to-DVD backup without parity, but not for critical data (long-time multi-TB RAID5 user here). I'd still suggest backup up to DVDs with parity... yes, you can make RAID5-like parity for archives.
 
well....
its backup.
not everyones gonna put their data in a second location offsite like in a safety deposit box or on a backup storage server service so your pr0n may survive your house burning down...
it is a level of backup.
 
Originally posted by: 0roo0roo
well....
its backup.
not everyones gonna put their data in a second location offsite like in a safety deposit box or on a backup storage server service so your pr0n may survive your house burning down...
it is a level of backup.
Click to expand...

RAID is not backup. It's a online active solution to protect data at the most common point of failure. This is why "RAID0" is not really RAID at all. There's no redundancy or protection of data, unless you do backups. You need to protect your data by having multiple copies, at separate locations if possible, or not cry about it when your data goes kaboom, or up in smoke. Not everyone utilizes RAID and backups for pr0n either...
 
Originally posted by: 0roo0roo
well....
its backup.
not everyones gonna put their data in a second location offsite like in a safety deposit box or on a backup storage server service so your pr0n may survive your house burning down...
it is a level of backup.
Click to expand...

No it's not. It's redundant hardware, but not a data backup. If I delete everything from the array, there's no backup available. If a virus corrupts my array's filesystem or infects/deletes files, there's no backup. If a power supply fails or lighting hits and takes out my drives, there's no backup. If my system goes unstable and gradually corrupts all info going to and from the array (like some over-heating USB2.0 enclosures), there is no backup. For these same reasons, even mirrored drives are not backups.

Imaging onto a second drive that is routinely disconnected is a backup because you can revert to the imaged data if made at a point before the data loss. Mirroring that data loss or storing it on an array with parity doesn't protect against loss. The fault-tolerance provided by redundant hardware is meant to compensate somewhat for the increased likelyhood of an inevitable drive failure. Multiple drives INCREASES the chances of experiencing drive failure, therefore it does not protect one from anything but itself.
 
no, its a type of backup.
backup is redundancy period.
if my house burns down my dvd-r stack perishes.
if my dvd-r stack slowly goes corrupt because it was a bad batch of discs its toast.
does that mean its not backup?
of course not. you can honestly say that one shouldn't rely on one type of backup, thats a given. but to say its not backup is just playing games really.
 
Originally posted by: Baloo
RAID 5 is going to seriously reduce you performace, and is only suitable for a file/database service where redundancy is very important.
Click to expand...

That's not true at all. If you use a proper controller, RAID 5 can increase performance quite a bit. However, in order to enable things like write caching and what not, you'll need proper battery backup of both the system and the controller's cache as well.

That said, I've never had a SmartArray controller fail or cause an array to fail. I think the first step to not losing data is to have a decent RAID. If you're looking for a large size volume, RAID 5 or 6 is the only efficient way to go about it. Again, though, RAID is about fault tolerance and redundancy. It is not a backup. Any data worth saving should be backed up.
 
IMO RAID is a useless waste of money for any machine that's not a high-performance file server, and RAID is never a substitute for a decent backup. Ofcourse if you absolutely need redundancy and have a good budget for it, there are a lot of options.

If you do go with RAID, well, it depends a lot on what you need. RAID 0 is inherently unsafe (a single disk failure will destroy all your data) and is not really RAID at all. It sacrifices a lot of safety for a tiny performance boost. If you really do need RAID, I think RAID 5 offers the best of both worlds: it offers redundancy as well as fast reading, although writing is slower I think, and it doesn't recover from disk failure as easily as RAID 1.

This link gives a very nice overview of the various kinds of RAID and what they're good for. A must-read for anyone who isn't sure if RAID-5 is good enough.
 
Originally posted by: 0roo0roo
no, its a type of backup.
backup is redundancy period.
if my house burns down my dvd-r stack perishes.
if my dvd-r stack slowly goes corrupt because it was a bad batch of discs its toast.
does that mean its not backup?
of course not. you can honestly say that one shouldn't rely on one type of backup, thats a given. but to say its not backup is just playing games really.
Click to expand...

Nope. You totally missed it.

RAID1, 3, 5, etc is not about having backup data, it's about having backup HARDWARE that does nothing to prevent the majority of data-loss scenarios and only assists with catastrophic drive failure isolated to one drive. For example, RAID1 using two drives ensures that the system does not go down due to a drive failure, not that your data is safe from ANYTHING other than complete spontaneous drive failure of a single drive ("spontaneous" is key because a PSU problem or lightning strike will take out both). As mentioned already, there are many more ways for data to be lost than drive failure. It can't even ensure uptime without a host of other redundancies (redundant power supplies, backup power sources, etc). Do a tally of scenarios where people from this forum have needed data restoration advice on this forum and you'll see that a large percentage are from accidental formats, corruption, and other hardware failures.

As RAID0 and RAID5 prove, drive count != backups. If a two drive RAID1 array equates to a data backup, then does a two-drive RAID0 array + offline optical disc backup equate to half a backup? RAID5 isn't even close to a backup, so let's just continue using RAID1 for this example that RAID is never a backup (unless you have two completely separate RAID arrays that are synchronized manually or on a schedule but not mirrored).

You can interpret "Backup drive" to mean two things:
1) A spare drive
2) A second drive used to routinely backup duplicate data

Just like in RAID5, a second, RAID1 drive is an online spare drive that remains IN USE for 100% uptime. It is only ONE functional logical drive that remains vulnerable. In the event of a drive failure isolated to one drive, you still have one logical drive that remains without a backup. You had redundant hardware supporting/functioning as a single logical drive while that logical drive had no redundancy. Instead of having two pieces of hardware to support it, it now only has one. As we have demonstrated, hardware count doesn't equate to backups.

Would you say that the data duplicated in the memory of a second video card operating in SLI/Crossfire is a backup just because they are working together? Sure, those aren't data storage devices, but if the game crashes, you lose both... just like a drive corruption from the OS crashing would affect your so-called "backup" equally. If one card failed, you could take it out or disable multi-GPU to start gaming again, which similarly demonstrates that it is redundant hardware and not redundant data.

RAID1, 3, 5, etc keep a logical drive functional in a very specific scenario until it runs out of hardware redundancy. It's backup hardware, so don't call it a backup and don't ever treat it like it is.

I've had my fair-share or data-loss due to hard drive failure and I've had even more directly attributed to RAID arrays (more specifically, drives that weren't RAID-friendly). RAID introduces complexity and therefore even more can go wrong. Adding multiple drives for more capacity/performance introduces complexity and multiplies the chances of a drive failure, so redundant RAID arrays are only a step to prepare for that EXTRA vulnerability. The redundancy added by RAID is a step to minimize the extra vulnerabilies it introduced and don't do anything as far as providing a true backup.
 
i didn't miss the point. i'm quibbling over the narrow use of the term.

some raid does have redundancy. it is a feature to prevent data loss with failure...thats the point of stuff like raid 5. sure if lightening strikes and two drives die you can lose it all sure. your house can burn down as well with all your optical media as well. your media could be from a bad batch and you could lose it all that way as well. everything is vulnerable. but it doesn't mean that it doesn't qualify as redundancy. its just a matter of level of redundancy of course. if you want to go hog wild you could leave your data in a large fire proof safe in a storage unit away from your house if you wanted safer redundancy. hell why not include another copy in a nuclear bunker as well if you want to be really sure. thats fine. but its not fine to call everything that is less than that not backup.

as for more ways to lose data, sure you can always delete something by mistake. or have data corruption. but frankly no one i know has had data corrupted by hardware lately. if ever from what i remember. data loss is most likely from drive death. googles drive study does back this up showing drives just aren't all that reliable. from drive death raid does save you. if you have a card that supports a hot spare that automatically rebuilds the volume on failure then total data loss is even more unlikely.

like it or not, raid IS a backup. its not the ultimate recommended backup, but thats basically assumed that you will have other copies if you know how to do such things in the first place. like it or not restoring the data from optical media for several terabytes is not exactly a chore anyone wants to do. never mind the potential for a corrupt disc over almost 500 dvd-r's for 2tb is pretty high. so maybe you get to burn double that amount of dvdr if you don't buy a second set of drives. maybe you can't trust those drives to not suddenly be doa when you pull them out of storage, so double that as well. add fire risk, keep off site on a backup server as well.
yipee😛
 
Originally posted by: 0roo0roo
i didn't miss the point. i'm quibbling over the narrow use of the term.
Click to expand...
If you understand the details of RAID and backup well enough to quibble over definitions, then there's really no NEED to quibble. The problem comes with people who DON'T understand why RAID is not a 'complete' backup.

My clients who had all of their RAIDed drives STOLEN on a Sunday afternoon now understand why RAID isn't a complete backup.
 
RAID does not protect against viruses, stupid users (or stupid admins, for that matter), or an OS messing up big time. Backup does.

The main point is that it is ridiculous to use RAID's hardware redundancy when you don't even have a proper backup of your data. If you have two disks, don't put them in a RAID-1, but use one for the manual or scheduled backup of the other. When your server is so vitally important that it has to keep operating during hardware failure, it's also important enough to have a serious backup strategy with regular full backups and frequent incremental backups.

RAID is for when the very best is still not good enough. Using RAID with a crappy backup strategy or cheap hardware is just throwing away your money on the least efficient way possible.
 
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