Is Raid1 an acceptable backup method?

Discussion in 'Mac Pro' started by Chimpy, Mar 26, 2007.

  1. Chimpy macrumors 6502

    Mar 9, 2007
    I had always assumed that Raid1 was a good way to keep things backed up. I have something like 250GB of music, 300+GB of video, and 20+ GB of photos that I keep on various Raid1 sets. I thought that was decent protection, but a few offhand comments made on various boards have got me wondering.

    Backing up to removable media isn't an option - I don't have them time to do DVD backups of even the photo data at 20GB, never mind the music/video data. I need something automatic or I will no doubt forget to do the backups.

    I do realize that if I write corrupted data, then corrupted data will get mirrored. Is something like that a big worry?

    Anyone have any thoughts or ideas to help me out here?
  2. robbieduncan Moderator emeritus


    Jul 24, 2002
    RAID (of any sort) is not a backup. RAID is a way of increasing performance or mitigating against drive failure. A proper backup is taken to media that is stored separately from the main drive protecting against theft etc.
  3. jofallon macrumors newbie

    May 18, 2005
    Raid 1 as backup

    See for some possibly relevant info.

    I had a Raid 1 with 2 Seagate 250 gig drives (5 year warranty), using the OS X software raid. After a year one of them started showing a bad sector or two, and the array degraded to just use the other drive. I would never have known the one drive had a problem if I hadn't happened to check the system.log looking for something else. The drive never did fail the SMART test thing; but attempts to read those few bad sectors would just hang.

    Now I use the second internal drive as just another place to put a clone backup (in addition to an external firewire drive).

    Something like SuperDuper will do scheduled clone backups to the second hard drive whenever you choose. Just backing up files? something like DejaVu, Chronosync, etc will do that on a scheduled basis to another drive, local or networked. I do both of those.
  4. Chimpy thread starter macrumors 6502

    Mar 9, 2007
    AWESOME link, thanks jofallon. And thanks to everyone else that replied. I see now that I have to redo my whole storage system. :)
  5. apex macrumors newbie

    Mar 26, 2007
    I also don't think any RAID solution makes for a decent backup. When I'm backing stuff up, I think of three situations that scare me, and try to make sure I'm protected from them.

    1. A bad OS upgrade. RAID drives are physically connected to the computer, so they could be blanked if something goes horribly wrong during an OS reinstall or upgrade.

    2. Accidental overwrite or erasure. You already realize overwriting is a possibility, so I'm guessing you're OK with manually avoiding this one. (And yes - I know there's a trashcan to catch stuff, but I've occasionally had programs not use it, or sometimes I toss something really big, like a badly encoded video in there, and I'll empty the trash manually.)

    3. House fire. Both drives are toast, and all your 20 GB of pictures have melted away. *sob* This one's got me the most worried... lotsa baby photos these days.

    I'd say backing up is a multi-level thing. Get a nice offsite backup of the really important stuff. (Like baby photo's and tax records.) Go buy an external hard drive, and store it a friends or your parents or something. You only need to refresh this backup once a year or so. (Tax time makes a great reminder for me.) I personally use DVD's but I have less data than you.

    I have a separate computer I do backups to over the network throughout the year to handle a bad OS upgrade. (I just use the .Mac backup software, so I don't really have to remember to do anything. It prompts me once a week.)

    I also have Quicken do encrypted backups to .Mac after every close, but that's mainly because my wife uses it a lot, and she practically LOOKS for reasons to hate computers, so I don't want her to lose much of ANYTHING if she loses the drive in her macbook. If she had a RAID I might not bother with that.
  6. mrgreen4242 macrumors 601


    Feb 10, 2004
    Er, you're mistaken. You can have RAID drives which are just mirrored, this adds no speed, or capacity, but is a great backup. You can have RAID drives that are striped with no redundancy, which adds speed and capacity, but no back up. There's also modes where you have striped data, AND there is checksum data as well, which lets you rebuild an failed drive with data from the other drives in the array and the checksum data. It adds speed, capacity, and backup protection (although not 100% protection, as it only works if one drive fails, but if two go at once your SOL).

    This is the best advice I've read on backing up. A RAID drive is a great first level of backup, but on the other hand so is an external drive and a good backup application (Time Machine...) would serve the same purpose, but also give you some leeway in grabbing an accidentally deleted file before the next sync is done. Always do regular backups of important files to optical disc, and update them every 6-12 months (optical media WILL go bad). I also recommend taking either a duplicate set of the optical backup, or the old set at the least, and storing them off-site. I keep my home backups at work and my work backups at home, for example.
  7. trainguy77 macrumors 68040

    Nov 13, 2003
    RAID is only designed to protect against HD failure, and also give speed increases nothing more. Its designed to keep mission critical things online 24/7. This allows servers (and some desktops) to get both a speed increase AND the ability to hot swap dead drives. Speaking of which I have a dead drive at work...what a nightmare.
    Also RAID can be alot of trouble in some situations. Think twice before setting up RAID.
  8. rhoydotp macrumors 6502


    Sep 28, 2006
    hmmm ... redundancy, no downtime, performance. i wonder why you would have to think twice about any of these :confused:
  9. trainguy77 macrumors 68040

    Nov 13, 2003
    Well what they don't tell you about RAID is if a drive fails it has to be replaced with a drive with the same size or larger. So currently at work we are stuck in a situation where our drives are all 18.4 g 10k scsi drives. Well we had a drive failure....or replacement drive is a dud. Well these drives can't be found these days as they were a rare drive back in the day. So now all we can get our hands on is 18.2gig drives which can't be put in the array. So now we have to rebuild the whole system with 18.2 gig drives. As we can't find any drives larger that work with our scsi interface short of going with something much to big. And you may ask why keep something so old? its a document server(word etc) so 60+gbs is fine(after raid 5) and its still a decent server 1.25ghz dual. Fine for our needs. :D So i have heard some people kicking themselves for going RAID when they didn't need it as then they got stuck later on finding a replacement drive. Just make certain if you do go RAID go with a very common drive. And if you can drop the size of the array from using the whole disk to using like 95% as sometimes even within one size hard drives can differ a little. even 10 mb can cause the problem depending on the controller.:(
  10. rhoydotp macrumors 6502


    Sep 28, 2006
    fair enough. but then again, if a device is not supported anymore, you should really think about of getting something supported & readily available. much like if you have your tape backups on reels, you should start thinking about moving them to lto. anyhow, good luck with your problems
  11. CanadaRAM macrumors G5


    Oct 11, 2004
    On the Left Coast - Victoria BC Canada
    Oh my, did you not read the rest of the thread?

    The ONLY thing RAID 1 protects against is ONE of the drives in the RAID set failing hardware wise. This is not = to backup.

    As mentioned above, if you have any procedural catastrophe (deletion, overwriting a file, accidentally saving a change that you didn't intend, virus, crash that corrupts OS or data, bad RAM or other hardware that causes corrputed data to be written) Then the Mirror drive is instantly just as $cr3w3d as the Main drive.

    If you have an external failure, like the powersupply in the machine or the RAID enclosure, or a fire, or theft, you are also hoovered.

    No System Administrator uses RAID instead of backup; it is always used IN ADDITION to an offline (and somtimes a near-line) backup plan. A good backup strategy incorporates both data that is nearly immediately accessible, and data which is offsite in longer term archival storage.

    So something like:

    1) All archival files burned to DVD and stored offsite (Labelled and catalogued)

    2) Monthly DVDs burned of all active files (including email databases) and stored offsite

    3) Daily or weekly rotation between off-site storage and onsite of a portable hard drive or cartridge with active data.

    4) Nightly automated backup from the main machine(s) to a server or a backup drive of active data

    Then last, but not least,

    5) RAID 1 in the main machine(s)

    Everybody should be doing 1 and 2 at a minimum

    3) used to be done on backup tapes, but tapes are too slow and hard drives are now large and cheap enough. A 2-bay hot swappable external Firewire or SATA enclosure works well here.

    4) Every professional computer user should be doing this; if you use your computer to make a living, and your data has value, there is no excuse not to have an external hard drive, or a network attached storage device, and run a backup utility nightly.

    5) Is nice if you have the chance; but it is almost pointless without 1,2 and 4.
  12. trainguy77 macrumors 68040

    Nov 13, 2003
    Yes this is true...but not all non-profit organizations can buy another server for $3000. :( BUt we have found a bottom less supply of compaq 10ks for free. :D So after our image rebuild we are doing thursday we will have a ton of them for free.
  13. mrgreen4242 macrumors 601


    Feb 10, 2004
    OK, so you have a crappy hardware setup so all RAIDs suck? Building a small RAID for home use with standard desktop parts is going to give him redundancy and protection against hardware failure. It won't be hard to replace the equipment, you'll be able to buy PATA or SATA drives in 10 years from now.

    Now, I agree that a RAID isn't a 100% backup, but no method is. If you backup to tape you can be hosed if the tapes fail (happens); DVD backups an suffer the same fate - disc rot, cracking, scratching, whatever.

    The number one thing a HOME user needs to backup against is drive failure. A RAID is a great solution to protect against that. That doesn't mean you shouldn't back up important FILES and DATA to another device, but it will certainly help you have limited downtime and data loss due to hardware failure.

    Hah. I'm in the same boat. I work for a non-profit as well, and we have a very similar array for a file server. Luckily they are all working OK at the moment, but once they start to fail, unless I get lucky and find a bunch of cheap ones, I'm going to recommend they scrap it and replace it with a simple RAID 1 SATA setup using a pair of 500GB drives (coupled with our normal tape backups, of course). We only have 25 users and they are using 10Mbit ethernet, so the speed isn't really a huge issue for us. I'll probably move the domain services over to the database server and use a G4 PM or something for the file server.

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