Any issues with RAID 1?

[thilanliyan]

Are there any issues one should be careful of when using RAID 1 when it comes to data integrity?

 

[Blain]

Originally posted by: thilan29
Are there any issues one should be careful of when using RAID 1 when it comes to data integrity?

Yes, there are some issues...
RAID 1 only protects against a HD failure.
* If corrupt data is written to one drive, it will also be written to the second drive.
* RAID 1 is not considered a "backup". Backup your data to another removable drive or use something like SkyDrive, ADrive, Mozy or Carbonite.
* RAID 1 can't protect against electrical problems that originate from your powerline, for that use something like the APC LE1200.

 

[taltamir]

I would point out that if you are trying to decide between a backup and raid1, do raid1 instead of a backup... but that is a false choice!
You should ALWAYS do both!

The only way to protect against corrupt data and power fluctuations is to use ZFS or the google FS. Since google is keeping its file system as a trade secret, you are left with ZFS. originally solaris only, it is being ported to freeBSD and the server class macs (in snow leopard i think).

Anyways, issues be beware:
1. bit flip, a random ray of solar radiation will flip your bits on magnetic media...
2. A virus can still damage your files
3. accidental or intentional user deletion.
4. random errors in writing data, the best of spindle drives say they will write one byte out of every terabyte wrong. For this figure to remain where it is for so many years would have required manufacturers to make tremendous advances in reliability as drive sizes went up. I suspect that like the MTBF (137+ years on any drive) it is grossly misleading. Basically expect random and silent data corruption...

And as i said before, all of those can be dealt with by a good file system... only two in the world that do though are the google file system and ZFS

 

[thilanliyan]

Thanks very much for your responses.

I just finished installing a RAID 1 set with Win7 RC1. Now that I thought about it, the chances of both drives failing are higher than if one was just used as a backup right (since you are constantly writing to both drives all the time instead of a backup once every couple of days)? I might just go back to a regular setup with making backups every couple of days.

Is there any backup software that sort of just updates files that were changed and deletes files in the backup that were deleted in the original instead of having to do it all over again? Does Windows 7 backup do this?

I'll read up on ZFS.