RAID5 Extension

[Florian Rhomberg]

Hi,
I have a very big problem. We have an HP ML370 G4 Server with 6 harddisks (4x72 GB RAID5, 2x143 GB RAID1). Therefor I had about 208 GB on the RAID5 array and 143GB and the RAID1 Array. Now I replaced step by step all 72GB harddisks with 300 GB harddisks because we needed more space. As far as I know this should not be a problem. Then I wanted to extend the array and started the Array Configuration Utility. And there is my problem. My controller shows me at the moment two logical devices. The RAID1 array with two 143 GB and the RAID5 array with 208GB. An then there is the new free space which is not a part of an array. But the free space has only a size of 312GB and when I try to extend the existing RAID5 Array I can only get about 480 GB with four 300GB harddisks. That is nearly the half. When I click on more information there are 4x300GB harddisk listed in physical device 1.
Where is the problem? I should have about 900GB.

I hope someone can help me because it is a little bit strange to tell your boss that you bought 4x300GB harddisks and afterward you have only about 500 GB and you don´t know why.

Florian

[TY 007]

Hello Florian,

ML310 G4 Overview:
http://h18004.www1.hp.com/products/quickspecs/12570_div/12570_div.html

Please advise from above link, which Controller is used for the 4x300GB HDs?

Thanks

[Florian Rhomberg]

Sorry I forgot to notice the used array controller. The server uses the Smart Array 641 Controller, firmeware version 2.68.

Florian

[SPa]

Hi,This definitely looks strange.

If possible,post the Physical and Logical view screenshots from the Array Configuration Utility.

[Florian Rhomberg]

Hi,
this is the screenshot of the utilty software. I hope this will help!

Florian

[Florian Rhomberg]

And this is the view of information display:

Florian

[SPa]

Hi,

I think I know the reason now.

You have all the six drives in a single array.This means the effective Physical Hard Drive space in the array is 146 X 6 .

The correct configuration would have been to have two seprate arrays.
Array A = Raid 0+1 which includes 146*2
Array B = Raid 5 which includes 300*4

Your current configuration breakup is as below :

Total Space available in Array A = 146*6 = 876 GB

Current Logical Drive 1 which is a Raid 5 has a size of 203.49 GB
Parity Size reserved for Raid 5 would be 1/3rd of the Raid 5 size which will be 67.83

Current Logical Drive 2 which is Raid 0+1 is 135.66
Mirrored Space would be the same = 135.66

If you add all of them that is 203.49+67.83+135.66+135.66 = 847.48

This is somewhat closer to the 876 Mark.The difference will be in terms of the calculation which the smart array does internally.

Overall,the difference you are getting is because of the fact that you have all the Hard Drives in a single array.The correct way would have been to have different size drives in a different array which is what the rule says that is to have same size drive in the same array else the smaller drive size is taken as the default and the more space is wasted.

[chongkan]

After extensive research I can't find a reason for this behavior, the only think I could think about is that for some reason the 641 currupted the RAID 5 and teh only resolution I can think about is:

1- Back up RAID 5.
1.5 -> Upgrade firmware for the 641 to latest.
2- Turn server off.
3- Take RAID 1 (OS) HDDS out and remeber their positions ( slot positions )
4- Delete RAID 5 with ACU and recreate it. ( At this point everything should be fine ) Save all changes.
5- Turn off server again.
6- Place RAID 1 back into its original position.
7- Turn on the server. It must recognize the RAID 1 config from the HDDs.
8- Go to ACU and create logical drive for RAID 5.
9- Restore RAID 5 info.

------------------

About previous comment:

Before changing the 72 GBs drives for 300 GB drives they were a mix of 72 and 143 in the same array A. Same situation as now but with different sizes and it was working fine as it should..

[SPa]

All I can say is earlier also the 146 drives would have been used as 72 GB and not 146 GB..

Recreation into a single array again with a mix of 146 and 300 GB drives will again result in the same amount of space available.You may want to try this in a spare server if available.

There should be two seperate arrays for Raid 1 and Raid 5.

[SPa]

To make things more clearer

Earlier configuration was 72*4 + 146*2

Now as they were in a single array,total space available for Logical Drive creation was 580 GB(Add 72*4+146*2)

Out of which the Raid 5 space was 203.49 GB and Raid 1 space was and Raid 1 space was 135.66 .