Proliant 1850R RAID question

[Neil Parks]

We have four Compaq Proliant 1850R servers running Red Hat 7. Each one has four 18.2 Gb 7200 rpm Wide Ultra 2 80-pin drives for RAID striping. Some of those hard disks are starting to fail.

If we need to replace one, does the replacement have to be an identical 18.2 Gb 7200 rpm Wide Ultra 2 80-pin drive? Does it have to be the same Compaq model? Could we insert one with larger capacity or faster speed if we can't get an 18.2/7200?

[Igor Karasik · Accepted solution]

Replacement disk does not need to be identical by size/speed.
You can use disk with larger capacity/faster rpm.
The speed will be automatically limited to the lowest common speed within a RAID set (7200 rpm in your case).

[Roger Faucher]

Like Igor said, you can go with 36GB, 74GB, etc. Once you've replaced all of the drives in an array with larger drives, you should be able to allocate the "lost" space for use by the system. That's why it's a good idea to be consistent when you replace drives. We actually move drives between servers (one at a time, of course) to take advantage of the 'lost' space situation.

Make a great day!

Roger

[e4services]

As they has said above, the replacement drive only is limited in size to the size of the other members of the set, the new drive, though larger, gets truncated to the size of the other members.
As for the speed, the statement "The speed will be automatically limited to the lowest common speed within a RAID set (7200 rpm in your case)" is not correct. The rotational speed of the drive is a function of how fat the drive itself can read/write data to itself (effect on access time) and is in no way a function that is aware to the rest of the system. All drives usually have a bit different access time, 3-5 ms. The effect of one higher rotational speed drive is that it will complete its tasks before the other drives. The system speed will not be effected until all the drives in the set are of an increased speed.

[Bob Stone`]

So, what you all are saying is that replacing the 18.2 / 72000 rpm drive with 36 /10k rpm drive will be just as easy as hot swapping the drive.

What about the original drive being a ultra2?

Does the replacing drive(s) need to also be ultra2 or can they be something else supported by the SCSI controller?

[Roger Faucher]

Bob:

See if this table helps. Pay particular attention to the Note following the table:

http://tinyurl.com/83lqv

Make a great day!

Roger