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Replacing drives in an Array with pre-used drives

Jeff Wilson_3
Occasional Advisor

Replacing drives in an Array with pre-used drives

Can anyone advise if drives that still have data on and have previously been used in unknown array formations should be used to replace failed drives in Raid1 or Raid5 arrays ?

We have a number of old drives and would like to use them as spares but if they shouldn't be used with data still on them, then how can we format them so they effectively become "new" and ready for use ?

Also I have heard numerous rumours that data being rebuilt on a newly installed drive in an array can be lost by the recon drive copying its own data back across the array instead.
Can anyone confirm or refute this ?
Ay help or advice would be appreciated.


5 REPLIES
Peter Godron
Honored Contributor

Re: Replacing drives in an Array with pre-used drives

Jeff,
what OS are you using?

Under HP for example you would at some point run a newfs before adding the disk into a RAID. So when you add the disk YOU determine which is the original and which is the secondary.

Regards
Jeff Wilson_3
Occasional Advisor

Re: Replacing drives in an Array with pre-used drives

Apologies for not making myself clear.

All drive arrays are connected via a controller such as 3200/5400/6400

As the Arrays are being rebuilt at a hardware level the O/s is almost irrelevant. My concern is that the hardware firmware won't be able to distinguish between old data and new data when old data exists.

Similarly as the old drives also had SCSI Id's assigned at what point is this erased ?

So basically, If I insert a drive from part of an old array as a replacement for a failed drive in a new array is there any danger to the data in that new array ?

has anyone had experience of this causing a problem ?





Uwe Zessin
Honored Contributor

Re: Replacing drives in an Array with pre-used drives

I think you are safe as long as you plug the drives while the power is on and then immediately put a logical disk on them to overwrite the old metadata. Else, the controller might suspect a drive roaming on power on and choose the wrong set of meta data - oops :-(

The SCSI ID is not recorded on the disk - it is provided by the backplane connector.
.
Jeff Wilson_3
Occasional Advisor

Re: Replacing drives in an Array with pre-used drives

Thanks for the phrase "I think it should be safe". That puts my mind at ease :)

anyone else.....
KurtG
Regular Advisor

Re: Replacing drives in an Array with pre-used drives

This depens somwhat on how the drives where used in the previosly system.

I.e a singel disk with a singel volume will contain valid smart-controller data. As so, the Smart controller would "import" it.

If the singel where used as part of a Smart controller array, the smart would still se that the disk is supposed to be member of a array with som other disk that are not present.

The last time I checked with HP (Some years ago now), they only supported "unconfigured" disks. This does not mean that it would not work, but they surtenly would not do any testing on this.

However, if you have access to a Smart controller you can easely removed the "array configuration" data from the disk (if present). The Smart controller will "import" the disk as a broken array. If you delete the broken array, you'll also remove this information from the disk(s).

Hopfully this helps you somewhat?

KurtG