artifect

Hi

I am new to RAID configuration. I am having this hardware RAID1 configuration with adaptec 2100s controller with two 18GB SCSI HD. My mirrored drive is having problem so i intend to replace it. But the closest i can get is 73GB from Seagate. My questions are :

1) Do i need to get one 73 GB or two ,since only 1 of my currently HD is faulty? i read i need two identicle HD for mirroring to work is that true?

2) Can i just plug in my 73GB and use the utility to rebuild onto this new HD?
Or do i need to use windows backup with ASR, install windows on the new HD and restore my backup ?

3) Currently i only purchased one 73Gb..... dont know how to continue, please help me.

Thanks

pilotbrian0

1) TECHNICALLY: you can run with mismatched harddrives on a good raid card (it varies from card to card but most will just limit the overall capacity to the smaller drive).

2) You should be able to just rebuild onto the new hd IF your raid card is willing to let you go with mismatched harddrives.

3) The best bet is to try it, and if it works, you're set. I would however recommend, for multitude of reasons, get a second hd and start over. Back up your files, reinstall windows on a new raid of two matched hd's and restore your files. You'll find increased stability and performance, and if you ever expand beyond the 18 GB (not too hard with xp, almost a walk in the park with vista) you will already have the hardware in place.

The simple fact is that you are correct, 18 gb is way obsolete. I'm running a 300gb (non-raid) in my box.

artifect

pilotbrian0 thank you very much for the reply ! MY manager is jumping when i told her i might need to purchase two HD! Actually the station involve is a production PC( they will need to shut down the production line inorder for me to do that!) Therefore my repair must be short .. the station is old and dont think it comes with the original windows 2000 CD.

So i bet my best try is

1) to go ahead to rebuild using the mismatch option
2) Use the reinstall option, BTW how to back up with a ASR option?

artifect

eh ... sorry another questions. Is the size of the hard disk supported dependant on the RAID card or the PC bios? ITs an old pc now i am worried it might not support 73 GB .....

pilotbrian0

If you have the 18 gig card and are using a raid card separate from the motherboard (you plug into a isa or pci slot) then it doesn't matter as the motherboard will only see a 18 gb harddrive.

If it is an onboard raid card (you plug the drive straight into the motherboard) then you may run into trouble but it is unlikely. Typically what happens is additional platters or clusters are simply not recognized so your drive will appear as a 32 gigabyte drive.

As to the backing up, you'd have to ask someone who is more knowledgeable about such things, as I have never tried to do anything close to a full backup. I copy my documents to a dvd and reinstall.

artifect

Oki thanks!!

linderman

in your shoes given whats at stake (production line server) / I would look on ebay for a matching hard drive & model you could then clone the living drive and put it back into the raid ??????

artifect

oh... i already purchased a bigger hard drive. Will there be any problem using a mismatch drive?

linderman

you never know until you try

its quite a risk to freak out the controller from mismatched drives ????


I would not chance it myself; given your ears will ring if you cant get that production line server back up quickly,


you should be able to buy the exact same model drive off ebay used even,


I have never heard of mirrored drives that werent identical ?????

pilotbrian0

Just to clarify, I have a linux box using a hardware raid that has mismatched drives... (It's a box thrown together from spare parts lying around). It's nothing fancy, just a basic mirror, but the catch is that the raid controller doesn't even care what size the second drive is, at least with the one I have. It will simply not use any clusters beyond those used on the primary. One thing to note, a Raid 1 doesn't usually work based on size but on cluster size, so if the cluster sizes are the same, there is no reason why a Raid controller can't figure out what to do with a larger harddrive in the secondary slot. In the primary slot however could be a problem.

Of course, if the primary ever goes out, I'll need to either replace the primary with a matching drive to the secondary, or break the raid.

linderman

Pilot's reasoning makes sense. give er a whirl and let us know

kraftwerk

Hiya, just my two cents worth here.

In all cases, first do a full backup. If you don't have a tape/disk backup regime, make sure that the stuff on the drives showing up in Explorer are cloned/imaged somewhere.

If only one of the two original drives is faulty in a RAID1, replacing the drive and going into the RAID controller software should enable you to rebuild.

Regarding the HDD sizes, if the old drive is 18GB and the replacement is 73GB, all you lose is drive space, since RAID will only use 18GB of the new drive. However, if you get two 73GB drives, you should be able to a) restore the initial RAID1, then b) clone/image the contents as before, swap the remaining 18GB with a new 73GB and c) let the controller rebuild the container. Then it should be possible to use the unused 55-ish GB to create a new container and eventually populate that with new data.

I'm not familiar with the Adaptec 2100, but considering an older Adaptec 29160 is only around US$70, and a new Adaptec 39160 is about US$130 on eBay, it might be useful to update the RAID controller as well.

With the higher-end Adaptec cards, a RAID5 or RAID 5+1 configuration would be a more feasible (and safer/faster) configuration for the future.

artifect

hey thanks for all your reply! i am going to try it out tomorrow.... after solving yesterday's windows corruption on that pc due to a unforseen reboot!! Now then i realise failover will not happen if it is a software issue ..........

I have checked again the status of both the hard disk now shows good ont he RAID management software, should i replace the supposing not working hard drive or attach it as a hotspare instead?

How to assign another PC to take over in such a situation?

artifect

hi all,

I replace the 18GB mirrored with the 73GB and carried out a rebuild. Everything is good. Ipower off the machine, plug out the SCSI ID0 power and data connector and restarted the pc to test the failover, it didnt work..... ... it just hangs there.