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[ecb]

Hi, I just set up a DNS-323 yesterday for my home network.  I am using 2 1 TB drives (WD1001FALS).  The drives are currently set up for RAID 1 and I enabled the Time-Limited Error Recovery to help keep the system from trying to rebuild the RAID (see http://www.hardforum.com/showthread.php?t=1285254 for some info on this).  Setup went well for the most part though I had a hard time connecting to my XBox 360 until I installed fun_plug and Twonky.  Now that works well and network access speeds are reasonable enough.

My main question revolves around backup strategies.  One of the reasons I picked this NAS was because of the built in RAID 1 capability.  However, the more I read the more concerned I am that this isn't the right way to configure the system.  This isn't being used for anything "mission-critical" but I am using it to store a lot of things that I'd hate to lose.  The other option spoken about here pretty often is a straight volume copy between drives.  My questions are:

1.  Is the volume copy handled by "Scheduling" option of the DNS-323 configuration page?

2.  How long does it typically take to sync between the drives when performing a volume copy?  Obviously this is dependent on the amount of data/# of files that have changed, but if people can give some real-life numbers and experiences that would help.

3.  How much degradation in performance should I expect during a volume copy?  It's hard to predict exactly what are good times for performing this operation as the drive could be used pretty much any time of day.

4.  Can someone summarize the pros/cons of both the RAID and volume copy methods?

I'll probably also use an external HD to back up the really critical stuff, but I'd hate to spend all this money with the expectation that my data is secure and is to recreate when there's a HD failure only to find that it's impossible to rebuild the drive once things go wrong.

Thanks!

Ethan

[bigclaw]

4.  Can someone summarize the pros/cons of both the RAID and volume copy methods?

It's not that useful to compare the pros and cons of these since what they offer are vastly different. RAID1 gives you continued availability of the data in the event of a single drive failure. Periodically backing your data up, well, gives you data backup.

Consider the following scenarios:

1. Your primary hard drive fails.

If you have:
No RAID1 and no backup: you're screwed.
RAID1 only: continue accessing your data without interruption. Data is vulnerable.
Backup copy only: cannot access data until it's restored from the backup copy. Data is vulnerable.
RAID1 + Backup: continue accessing your data without interruption. Data is not vulnerable.

2. You accidentally deleted all your HD movie collection.

If you have:
NO RAID1 and no backup: you're screwed.
RAID1 only: you're screwed.
Backup copy only: cannot access data until it's restored from the backup copy. Data is vulnerable.
RAID1 + Backup: continue accessing your data without interruption. Data is not vulnerable.

I assume data is vulnerable whenever there's only one copy, not vulnerable if two copies.

[Zardoz66]

I work with RAIDs on the enterprise level everyday. The thing to keep in mind is that a RAID1 is not a "backup" it is redundancy, and you are still very susceptible to data corruption across the RIAD. Even in the event of a drive fail the raid can become corrupt, this does not happen all the time, but it does happen and I deal with it everyday in my job.

The volume copy IMO is much better suited for the home as it copies "backs-up" data from one drive to the other if NAS the main source of storage, but if you are using the NAS for a backup device, then a RAID1 one would be OK as the NAS is being use to backup the main data. this would just give you an extra level of redundancy on the backup.

[ecb]

Thanks for the replies so far - they've given me a slightly different way to look at things.  Right now I'm leaning towards the volume copy method, along with an external USB drive for critical backups from the 323 just in case something goes terribly wrong with the entire device.  I do have concerns that a corrupted RAID network would make it impossible recover from either disk while having 2 drives working independently with volume copy seems the simplest and safest overall.

Does switching the setup from RAID 1 to 2 separate drives force you to format the discs?

[ecb]

Also, does the incremental backup work with fw 1.06?  I'd rather not do a full copy of a few hundred GB of data every day when only a very small percentage of that will ever change.  I saw some mentions in older threads that incremental didn't work well, but I don't know if they're fixed now.

Thanks!

[Zardoz66]

Yes you would need to resetup the disks going to a single disk mode. as to the incremental not sure if that works as of yet. I am still looking at it myself.

[fordem]

After you back up the data, but, before you reformat the disks - try this - remove either one of the disks and then format the other one.  When the format is complete, restart the unit as prompted and then shut it down and reinstall the disk that you removed earlier.

If I'm right, the unit will recognize the second disk without prompting to format it, and you'll have your two standard volumes - worst case scenario is I'm wrong and you'll need to format the disk and restore your backup, which is what you would have had to do anyway, best case scenario is I'm right and you save the time required to do one format and the restore.

Let me know how it goes.

[blastro]

I contemplated the same questions and went for no RAID and using scheduled incremental backup for a couple of folders totaling approximately 200GB for all of the above good reasons. (I have 2 WD 1TB drives and firmware 1.05)

Daily scheduled incremental backup starts at 3AM and when I am getting dressed for work at 7AM my DNS-323 is still chattering away.  I haven't noticed any problem accessing data in that time but it is also why I scheduled it in the middle of the night.  For me it is working great and I still pull what I care about the most onto a USB external drive occasionally.

[ecb]

Thanks for all the replies.  I have decided to go with the 2 independent drives and daily incremental backups between them, and will also do less frequent backups of the critical stuff to an external HD just in case.  I'm still copying data to the main drive so I have not seen how long it will take to do the incremental backup between the two drives in the 323.  I have a large number of files stored (at least 2 million) though I don't expect many files to change on a daily basis, so most of the effort will be just checking timestamps rather than full copies.

Oh and as for the suggestion of removing one drive, formatting, and then bringing the RAID drive in to avoid copying all the data again - I'd already gone down the path of formatting both drives so I couldn't test that out.  That's when I ran into the 94% format bug which forced me to downgrade to 1.04, format, and then upgrade back to 1.06.  At least I'm passed all that nonsense.

Thanks for all the help!  I'm pretty satisfied that this backup strategy will keep me safe.  I think the worst thing that could happen is a nasty virus but I'm generally pretty careful about how I use my PC and the occasional external HD backups (otherwise unconnected to a PC) should at least provide some security if that happens.