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Mirror Or Clone?

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I have a Win 7 system with twin Hitachi 1TB HDs and a 2TB Seagate HD which I use for backups.

I had planned to mirror the Hitachi drives but now I'm not so sure...

The mirror would be created in software by Windoze and as I understand it the overhead creates delay.

I am considering a weekly clone from the 1st Hitachi to the second instead.

That way the second drive is only written to once/week and is never read - which should leave it in great shape to take over when the first one fails.

That, plus the lack of delay is why I am leaning away from the mirror.

Either way the Seagate gets a full files/folders weekly backup of the 1st Hitachi with daily incremental updates.

Does anybody have an opinion on this or a better idea?

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Just opinion here, you are correct in that running a mirrored raid array comes with an overhead penalty. Not only does is slow down the read write process (probably not all that noticeable) but, a software raid uses a fairly good amount of total system resources in operation, this is where the real slow down is noticeable.

I see nothing wrong with your plan but instead of doing incremental backups I would opt for differential rather than an incremental.

The differences are:

Differential backup

A backup method used for saving data changes that occurred since the last full backup version within a backup.
A backup process that creates a differential backup version.

Differential backup version

A differential backup version stores changes to the data against the latest full backup version. You need access to the corresponding full backup version to recover the data from a differential backup version.

Incremental backup

A backup method used for saving data changes that occurred since the last backup version (of any type) within a backup.
A backup process that creates an incremental backup version.

Incremental backup version

A backup version that stores changes to the data against the latest backup version. You need access to other backup versions from the same backup to restore data from an incremental backup version.

Notice that a differential backup is based on a FULL backup rather than a LATEST BACKUP VERSION. So for full disk mode backups a differential backup is more appropriate.

Ah... ok.

From my old tape backup days when I was an ISP I had figgered that the difference was that an incremental used the state as of the last BU as a base and each differential went all the way back to the last full BU.

So that recovery steps on day 4 would be:
Full + inc1 + inc2 + inc3 under the weekly full/daily incremental method and
Full + diff3 under the differential scheme.

The trade off being ease of recovery vs disk space.

Is that in agreement with what you are saying?

I guess I need to spec my hardware in my sig too...
Both have Antec cases, Antec Earthwatts 380 PSU, onboard or minimal graphics, Win 7 Pro
PC 1 ASUS H87-Pro mobo, 8GB Corsair 1600 DDR3 RAM, Core i5-4670 3.4GHz CPU, 2 WD 750GB SATA3 HDD, 1 WD 3TB HDD
PC 2 ASUS P5K SE-EPU mobo, 4GB Corsair 1600 DDR3 RAM, Core Duo i3 3GHz CPU, 2 Hitachi 1TB HDD, 1 Seagate 2TB HDD
PC3 HP G6 lappie
PC4 I dunno, I'm thinkin' Raspberry Pi?

Yes sir, you got it. As I said though, just my opinion. For me incremental is great for folder/file, differential best suited for full disk/partition.

Your specs look good, thanks for posting them, would be nice if everyone would as in most cases they really help in troubleshooting.