scsi RAID

gardnerbartlett
gardnerbartlett used Ask the Experts™
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We have 4 scsi drives on an Adaptec RAID AAA-133U2. Three made up the RAID and the fourth was a hot spare. The second drive in the chain, scsi #1 went bad so the hot spare which was the fourth drive in the chain, scsi #3, took its place. I need to remove scsi #1 to return it to Fujitsu since it is under warranty.

Question #1
If I remove the second drive in the chain, scsi #1, can I leave the settings as they currently are for scsi #2 & #3
or do I have to change #2 to #1 and #3 to #2?

Question #2
the 3 functioning drives are 7200 rpm. Will it be a problem if the replacement we get is 10,000 rpm if that is all they have available. The current size is 18.2gb.
If the replacement is 18.4 will that be a problem if that is all that is available.
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Top Expert 2007

Commented:
I would get the Docs from the adaptec.com site and follow the recommendations.

I do not think that size or speed should be a problem.

Normally, you do not need to make any config changes for a hot swap, except to temporarily disable a drive.

I hope this helps !

Author

Commented:
This is not a hot swap. I will down the server, turn off the power and remove the defective drive. Then I will turn the power on and boot the server. I'd like to leave everything the same but If I have to I'll change the settings from scsi id 2 & 3 to scsi id 1 & 2.
Top Expert 2007

Commented:
I do not think that SCSI ID's need to be changed.

I would the Adpatec docs on how to do a swap, and see if anything needs to be changed in the config program.

I do not think that you will need to do anything to the drives at all !!

I hope this helps !
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Commented:
No need to change the IDs but if the drive being removed is the terminiating drive, you need to set the new end disk to terminiate.  If your cable has a seperate terminator block on the end of it, you don't even need to worry about this.

Actually, active terminators blocks give a performance gain to the SCSI chain, as opposed to just using the drive termination.  So you might want to get one just for the heck of it.
The SCSI ID's will not have to be changed. I had the same experiance with an Adaptec 2100 RAID controller that dropped a disk. The SCSI ID's were 0,1,and 2. I downed the box and removed the dead disk. I mis-jumpered the SCSI ID on the disk  and it ID'd to 6. I configured the new disk as a hotspare (w/ in the SCSI BIOS)and the array rebuilt fine and is running OK a year later.

I highly reccomend that your replacement disk be an identical disk (same part#) as the others or as close as possible to the original. I would replace that disk w/ a 7200 RPM, the disk space should not matter.

Author

Commented:
Its under warranty and we have an RMA so hopefully we will
get the same brand. I removed the bad drive last night and
did not change the scsi ID on the scsi id #2 & #3 and its
working. For $120 I can buy a similar drive from same
manufacturer but it would be a 10,000 rpm. The RMA will take a month and I'm uncomfortable without a current hot spare for that long.

Adaptec manual says they don't have to be same size(of course you lose the difference between the smallest and the size of the other two) but says nothing about rpm

before I award points does Magarity have any opinion as to whether the rpm(2 with 7200 and one with 10,000) will make
any difference.
The controller is responsible for all of the read and writes to the disks and it probably does not matter if the new disk is faster. I would call Adaptec T/S.

I would say you are probably OK to use the faster disk, but I'm paranoid and usually don't like to. I would go to the manufature of the controller and get it from them.

Sorry I couldn't be more help : (

Commented:
Every time I've replaced a disk under warranty, the manufacturer gives me the option to replace the disk immediately for a future refund as soon as they get the dead disk back.  They send a new disk right away and charge me for it.  When the RMA department gets the dead disk, I get a credit a few weeks later.  Who made this one that you are not getting the same option?

Author

Commented:
I had that option but could not use it. The RMA is in my bosses name and they wouldn't take my credit card since it is in a different name than the RMA name(I did it over the computer rather than over the phone). Its a fujitsu. Do you have any experience mixing rpm speeds in a RAID?
Top Expert 2007

Commented:
Since this is SCSI, then speed should not really matter since all the hardware controler is on the drive, not in the computer.
All a SCSI controller does is send standard SCSI commads to the drive and the drive exeutes them.

There is no closed loop, which is why SCSI is faster than IDE in the first place.

 I hope this helps !

Commented:
"Do you have any experience mixing rpm speeds in a RAID?"

Yes.  No problem.  In fact, you can look at it this way:  Having one drive already faster/larger than the others for "free" via warranty replacement is just that much less you have to spend when the time comes to upgrade the others.

Author

Commented:
All comments were good and usefull. Magarity was the first to definitively answer the scsi id numbering question so I'm awardng ponts on that basis. Thanks Sysexpert & shaolindau for your input

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