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Replacing failed raid 1 with different speed drive

Posted on 2013-05-29
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Hi,
Hopefully this is fairly simple.

I have a HP DL380G5 with a  HP Smart Array P400 controller (doing this from memory, not at system).  I have the system drives in a Raid 1 configuration using 2-Seagate ST9146803SS drives.  It looks like one has failed.

I found a drive locally,  ST9146852SS, that seems to be the same other than the rotational speed (specs below).

Is it possible to have two drives in an array that are of different speeds?

Seagate ST9146803SS - Savvio 10K.3 146GB 10K 6.0Gbps SFF Serial SCSI / SAS Hard Drive

Seagate  ST9146852SS - Savvio  15K.2 146GB 15K 6.0Gbps SFF Serial SCSI / SAS Hard Drive

Thanks,
--SM
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Question by:smantz
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11 Comments
 
LVL 88

Expert Comment

by:rindi
ID: 39204857
The different speed won't matter. You just won't get any advantage of the higher speed as long as you don't also change the other drive for one running at that higher speed too.
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LVL 98

Expert Comment

by:John Hurst
ID: 39204860
I would be inclined to keep the two speeds the same, lest you run into some hardware synchronization issues that depend upon matched speeds. I do not know if this is the case, but I would not take the chance.  .... Thinkpads_User
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LVL 47

Assisted Solution

by:David
David earned 800 total points
ID: 39204953
Actually you WILL get slight advantage with higher speed drive.  Every I/O on that disk will take less time than I/Os on the other disks.
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LVL 56

Accepted Solution

by:
andyalder earned 1200 total points
ID: 39205184
Agreed, fractional improvement with a faster disk. The controller does two types of load-balanced reads, if it is very busy it will split the reads between the two disks but if less busy it will send both disks for the data and take the first answer which is more likely to come from the fast disk.

Are you sure they are generic Seagate disks though and do not have HP's part numbers on them as well? HP load custom firmware on their disks with tweaked retry timeouts and slightly different capacity, generally smaller than the generic drive so that any other manufacturer's disk will also be large enough. If you upload an ADU report **as attachment** we can check what the controller sees it as. (ADU should be under Start-HP system tools if installed else it's under the ACU on the SmartStart CD)
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Author Comment

by:smantz
ID: 39205843
Well I'll try and remote in and if I' can't, it will be tomorrow before I'm back on site.  But I'll upload whatever I can.
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Author Comment

by:smantz
ID: 39205946
Here are the attachments from the ACU for the controller, hope they help.
-SM
ADUReport.txt
ADUReport.xml
ADUReportTransform.xsl
ADUReportViewer.htm
0
 

Author Comment

by:smantz
ID: 39206047
I do believe that these drives are generic as there weren't any drives when I received the unit.  If need be, I will  take the unit down and pull the drives to see if there is any HP numbers.
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LVL 56

Expert Comment

by:andyalder
ID: 39206165
They are indeed generic drives from that report rather than HP branded ones so you are right to use a generic drive as replacement for now.
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Author Comment

by:smantz
ID: 39206172
So you feel there really wouldn't be much of a risk trying and using this drive?
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LVL 47

Expert Comment

by:David
ID: 39206196
SAS drives are all enterprise class so are similar or potentially same quality disks.  There are a few minor firmware tweaks that HP makes, but what you have is good enough for RAID1.  Now if you were doing RAID5 with max config of disks then I would say just to buy HP.
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Author Closing Comment

by:smantz
ID: 39206208
These guys are great and if I could give more points, I would!!!  Thanks a million
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