BobAl

Newbie: RAID replication question

4 posts in this topic

Hi -

I am fairly new to setting up RAID systems so I am hoping that someone here will be able to answer a replication issue I have.

I had an HP MediaSmart Server with one System Drive and two 2TB drives in it. I had set the server up to treat the 2TB drives for RAID.

Recently the MediaSmart server started to fail (seemed like the System Drive, but possibly could have been the actual server hardware).

So I have purchased a new Synology system, set up with two 3TB drives, and connected the original 2TB drives via SCSI to USB cable to start transfer files over.

Here is where I've seen an issue: the data on the 2 TB drives are not exact replicas. One of the drives has far more data on it... I am now concerned that RAID does not actually do full copies? I am not even sure if the actual integrity of the files on the drives are actually ok (i.e. there are many files which are .jpg, or .mp3, but I have no idea if they can actually be opened now...)

Can someone shed some light on what may have happened here? Is this how RAID is supposed to work?

bob

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Are you saying the drives were configured as a RAID mirror and don't match? Sounds like the original server was seriously failing for a while...

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Yes they were configured to be mirrors.

no way to know if it was failing for 'awhile' - but as soon as any indicators came up, i never added anything new.

so i guess i have 2 questions

1 - how can you have confidence that files are replicated between drives? if I had lost the drive that had more info on it here, i would have been screwed

2 - even if files are replicated, how can you be sure that the integrity of the files are intact?

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All I can think of is that RAID controller was either very lazy or broken....RAID mirrors are supposed to always be in sync, written to simultaneously whenever data is added.

I suppose the drive with less data could have had a problem and the controller decided not to write to it any more at some point, but you should have been notified.

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