Raid 1 Hard disk expansion without loosing data.

[lcc_spyros]

Hello all,

I have the following issue,
I have an HP proliant server connected with an HP Storageworks MSA50 (10x143Gb) total 1.4 Tb in RAID 1 configuration ( 700Gb ). I want to expand the array by adding one more HP MSA50 (10x300Gb). I know that due to way RAID1 works i will take only into account the 143GB out of 300 GB from new disks. My question is how can i expand the Raid 1 array (addind these disks) without loosing any data of my system.

Thanks in advance,
Spyros

[TTr]

How will you be connecting the second MSA50?
Cascaded on the first MSA50 or connected to the second port of a P800 raid controller or a separate raid controller?

What kind of i/o requirements do you have?

If you cascade, you may run into i/o issues. All the i/o traffic from all 20 disk will be coming from the same x4 connector (4 SAS ports)

Alternatively you can replace the existing 146GB drives with the 300GB drives. Replace one drive and allow it to rebuild before replacing the second one.

[lcc_spyros]

Hi,

My plan is to connect the input of the new MSA50 to the output of the already installed MSA50 and try to expand the raid 1. I was wondering if i could do the expand through HP smart array utilities or any other way..

[TTr]

Yes you can expand the existing array using ACU. This is a function of the raid controller.

Which controller do you have?

What server is this on?

Usually the raid controller must have BBWC installed to be able to do online operations on the disk arrays. It will be a very lengthy process to expand an array from 10 disks to 20 disks.

[lcc_spyros]

Hi,

We have HP Proliant DL385 G5 and G2.
The controler we are using is the P800.
I saw in an other forum that the procedure may take 1,5 to 2 days, is that true ?
Is there any manual from HP with the procedure of raid expansion ?
And one more thing is that Windowms 2003 server OS has hard disk capacity limitation to 2TB. By expanding the disk fy final capacity way overcome this limit. Is it possible for my system to recognizing partition sizes greater than 2 TB ?

[lcc_spyros]

Hi again,

I found the procedure, seems ok,
What wonders me now is if my system can recognize all the disk capacity.
There is a workaround method for recognizing partitions >2TB but it requires disks to be changed format whitch in this case all data will be lost. Any idea about that ?

Thanks in advanced.

[TTr]

Yes the process is very lengthy, I would say it can take more than a couple of days and in that time you will have degraded i/o. And if anything bad happens during the conversion, prepare to restore.

Now for the partition size, yes you have the 2TB limit in Win2003. You can convert to GPT (GUID Partition Table) format type but you have to backup and restore the data. There is no conversion tool that I know of, the conversion process is to delete the old MBR partition and create the new one using the GPT type. (Based on the nature of the conversion, I doubt a tool would exist, once the MBR partition is deleted there is no way to get to the data in the sectors of the MBR partition so that it could be copied to the GPT partition).

http://technet.microsoft.com/en-us/library/cc773223(WS.10).aspx

http://www.microsoft.com/whdc/device/storage/gpt_faq.mspx

http://www.partition-tool.com/resource/GPT-disk-partition-manager/convert-gpt-disk-to-mbr-disk.htm

In any case I would stay away from GPT partitions because even if there are tools to manage them, something might come up in your environment that might not be able to deal with them.

See if you can find a different way to use the new space.

[lcc_spyros]

Hi,

Thank you for your support

Regards
Spyros

[TTr]

Now back to the MSA50. Does the P800 have an unused connector in the back? If so, it would be better if you connected the new MSA50 directly to the unused connector instead of cascading it to the existing MSA50. There is a big difference in the i/o.

If you cascade, the i/o from all 20 disks would be in the same x4 cable. If you direct connect to the P800 you would have 10 disks to the first x4 connector and 10 new disks to the second x4 connector.

Also, I don't know your specific space needs but is is better to create new logical disks in the new MSA50 (and use the 300GB space if you need) instead of expanding the existing logical disk. Each logical disk has its own physical i/o in windows (or any OS) so within the OS you will have more i/o streams. Actually I would look into creating more logical disks if you can use them. Smaller disks are also easier to deal with in other tasks such as backups and restores, data defragmentation etc.

[lcc_spyros]

Hello ,

Unfortunately due to our configuration we have to cascade the 2 MSA50.
Do we have a big impact using it this way (time required for expansion)?
Our scope is to create one logical drive with all the available capacity because thatâ s the way application works.
Using Array Configuration Utility tool on test server we manage to expand existing array
But we saw that it was created as second logical drive and not expanded to the existing one.
From this test therefore it was possible the second logical drive (array) that was created to mount it as a folder to the first existing logical drive.
As we already say that we need all capacity to one logical drive, can we create a second logical drive with 300 disks and then mount them as folder to the first one ?
Attached you can find some photos from our tests.