Software RAID question, and NAS box software question


  1. Posts : 97
    Win 7 Pro 64 Bit
       #1

    Software RAID question, and NAS box software question


    The more I try and learn about backups and safe storage the more questions I have.

    Here's my latest. I have two identical SATA III 1 Gb hard drives, designated "D Drive" under Win 7 64 bit Pro. They are under an Intel software RAID 1 on a Gigabyte GA-Z97X-Gaming 3 motherboard. All appears well. I have the OS and my two mail apps on C: Drive which is an SSD drive. I use Second Copy to automatically back up both mail apps to the RAID 1 D drives each night. I also use Z-DBackup to make a system image of the C Drive once a week, which it creates on the RAID1 pair. The RAID 1 pair (D Drive) with the system image is backed up to LTO4 tape once a week.

    What happens if on of the RAID 1 pair of SATA III drives fails? I guess the Intel software RAID flags a fault? I then have to work out which of the 2 drives is dead, and swap it out? What if an identical drive is no longer available? Will any 1 Gb or larger SATA III drive work, paired with the one remaining original working drive?? Does the RAID rebuild occur automagically? How long might one expect it to take?

    With a truly unlucky chain of events, leaving the PC dead or missing, say from a power surge, theft or whatever, and I just have my tape, how do I go about getting the C Drive image from it to a new PC? Do I run a repair disc, load the tape deck drivers and the SCSI card drivers (it runs on SCSI on an Adaptec card), then will there be enough "stuff" on the new PC to load the Z-Dat software and restore from said tape? I guess I should be brave and "create" a fault and see if it all works *BEFORE* a real world failure...

    As an aside, if the motherboard croaked and I had to replace it with a currently available one, can I be reassured another board would still read the software RAID 1 created hard drive pair?

    Finally:

    If I bought a new NAS box and put 2 SATA drives in it as a RAID 1 pairing, and at a later stage the box hardware croaked, would a different, currently available box necessarily be able to read the drives? I can't see much redundancy in them if this is not the case, as the risk of hard drive failure is just moved to the risk of the box hardware failing. I am not sure if I am understanding how they work correctly or not.... Thanks.
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  2. Posts : 1,872
    Windows 10 Pro x64, Windows 8.1 Pro x64, Windows 7 Ultimate x64 SP1,
       #2

    Welcome.

    Regarding your questions, first I want to say that RAID 1 is not a viable backup solution. Its only purpose is to allow a system to continue to operate with a hardware failure of one of the hard drives until that drive can be replaced. It is imperative to have the data on the RAID backed up elsewhere.

    If one drive fails, the controller will warn you so that you may replace the bad drive. It knows which one.
    Depending on the size of the drive, it can take many hours to rebuild, but you can continue to use the system as normal. The rebuilding is transparent.

    If you use dissimilar drives, the array size will be equal to the smallest drive and it is not guaranteed that all combinations of drives will work together. You may experience constant rebuilds or worse.

    I cannot comment on how to get your system up from tape. I have never used it. With other backup methods, there is usually boot-able media that allows recovering the operating system.

    Whether or nor another board can read what is on the RAID 1 will really depend on the controller. I have had luck using Intel controllers. In fact, the data was readable from a single disk without using RAID.

    I doubt if a different NAS could use the disks should the box hardware fail. You may be able to get the data though, by connecting one of the disks to a system that can read the file system used by the NAS.
    The redundancy is within the NAS while it is operational. It would be nice if you could just get any NAS hardware and use any set of drives from any array but that is not possible today.

    As you can see, there is no substitute for a good backup scheme. RAID is not it.
    If data is corrupted, it will be corrupt on both members of the array.

    RAID is good in servers where continued operation is a necessity. I gave up using RAID 1 years ago. To me, since I have no urgent reason to keep the data available in real time in case of a drive failure, RAID 1 is just a waste of drive space.

    I use this space for backups of critical data.
      My Computer


  3. Posts : 26,772
    Windows 11 Pro
       #3

    I would like to reinforce what pbcopter wrote. Raid is not a backup. He mentioned some of the reasons and there are more. You would be much better off using separate drives and alternating them for the backups. If, as pbcopter said, you get corrupted files, you will have a copy of your system without the corrupted files. I am not familiar with the tape backup either, or the programs you mentioned you use for backups. If you are using an imaging program for backups, it has to have a way of restoring the backup or it is of no help. Your backup programs should have a procedure for restoring the backups and I would encourage you to use it as a test and make sure it works.

    If you have data that is important enough to justify all the trouble you are going through now, why not use 3 of the drives and alternate drives for backups. If you are real serious about it, keep one drive in a different location for security. Then alternate that drive with the rest of them, so you always have a current backup in 2 locations.

    There are several ways to backup correctly. But, Raid is not a backup and a backup program is of no use unless you are confident that it can be restored easily in any circumstances.
      My Computer


  4. Posts : 97
    Win 7 Pro 64 Bit
    Thread Starter
       #4

    OK, many thanks for the replies. My critical files (e-mail and photos) are backed up to an external drive weekly. I have bought a SCSI LTO tape drive and will also be backing up to tape. One tape holds 800Gb native, and 1.6Tb compressed, although most data of course will not compress that much if at all. I have discovered there is "some reason" you cannot image the OS drive direct to tape. You have to image to an NTFS format hard drive, then put said image on tape. Then do the reverse to restore. Tape is just a double insurance in case a hard drive fails.

    Commercial quality hard drives is the thrust of another question i will ask later, as well as to *WHY* an OS drive image cannot be written direct to tape, as I am very curious as to the reason for that.

    Many thanks for taking the time to give such detailed replies. I did consider a NAS box but a friend had the actual hardware of NAS box fail, and his drives could not be read in a replacement. the original was, as so many PC things, obsolete. I believe a convoluted process using linux got the info off the RAID array in the end. This has put me off them!
      My Computer


 

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