Can't see Raid 5 drive

[pts242]

Dear All,

I have IBM system x3650 with four 6Gb SAS FRU 42D0638 300GB

I have configured RAID 5 (3 as virtual drive for RAID 5, 1 as Hot Spare)

I have installed Windows Server 2008 R2 on Hot Spare. My problem is when I look in to My Cmoputer I can not see my RAID configured drives there.

Please help me how to resolve this. Thanks in advance

 

[Ijack]

1. Hot Spares are exactly what they sound like. They are not to be used for the storage of operating systems, programs, or data. You are using a member of a RAID array as a standalone disk. This is not going to work (especially should one of the disks in the array fail!).

2. Have you installed the Windows drivers for your RAID card?

3. Do you see the array in Disk Management? You have to partition and format it just as you would a physical drive.

 

[pts242]

First of all thank you for your valuable reply.

1. Now I clear that I did the wrong way. I should have to create a partition in RAID configured drive and install OS on there. As of now my configuration is like this, Is there anything possible me to change the configuration without re-installing OS and re-configuring RAID.

2. How do I check that drivers for RAID card has installed or not?

3. No. I can not see the array in Disk Management.

 

[Ijack]

1. You could try removing the 4th disk from the array so that it is no longer a hot spare. It may then work, but it may not.

2. If you don't remember installing the drivers then they aren't installed. IBM servers come with an install CD containing the drivers. I don't know if it is still the same but you used to install the OS via this CD; that would take care of everything.

3. If you can't see the disk in Disk Management then almost certainly the problem is lack of drivers.

As you haven't done too much with the system yet I would be inclined to start over. Use the IBM CD to install the OS. You should plan in advance how you want to configure the RAID array - you could use them as RAID 5 + 1 hot spare, giving you 600GB; all 4 in one RAID 5 array with no hot spare, giving you 900 GB; or 3 disks in a RAID 5 array (no hot spare) plus the 4th disk standalone, giving you 900GB. The last would be, IMO, rather wasteful as it would be dedicating 300GB to the OS, which is much more than it needs. Which suits your purposes best is something that only you can determine.

Read the IBM documentation (if it's the same as it used to be it is very helpful) and plan everything out before you start the installation. And is there any reason why you are using Server 2008 rather than the latest version?

 

[pts242]

3. In Disk Management, I can see only Hot Spare drive.

I used to install Windows Server 2008 R2 with IBM installation CD only.

So I am going to re-configure RAID and re-install Windows.

I have question that:

1. What would be better? RAID 5 + 1 hot spare ? / all 4 in one RAID 5 array with no hot spare?

2. What if any of the disk failure happens in all 4 in one RAID 5 array?

Thank you,

 

[Ijack]

You really only need a hot spare if you absolutely cannot afford any down time. (In fact, you only need to use RAID if down time is not acceptable, but that's another discussion.) In a non-enterprise situation I wouldn't bother with a hot spare as it uses up one disk's worth of storage.

Bear in mind that RAID is not a replacement for backup and does not provide data security; rather, it provides guaranteed uptime. If that's important to you then fine; if not don't waste another disk's worth of storage on a RAID 5 array.

In the event of failure of one disk in a RAID 5 array, however many disks it contains, it will continue to function with slightly degraded performance; you now have no tolerance in the (rather unlikely) event that another disk fails before you can replace the first. Replace the failed disk and it will rebuild the array and it is back to normal; I would imagine that with your setup this can be done without having to switch the computer off or rebooting it.

I can't emphasize enough that RAID is not a replacement for a good backup strategy. Most data loss is not because of hardware failure but because of human error and/or filesystem corruption.

 

[pts242]

Thank you for your valuable reply and I got the points you described.

But having doubt that:
1. If I use All 4 in one RAID 5 array, what would happen if any of the disks fails in the array? (as per my understanding from your explanations that a slight degraded performance will be there and the other disk in the RAID 5 array will take action. But, If we use Hot Spare, no degraded performance, suddenly the Hot Spare will take action.) Am I right?

2. If I use All 4 in one RAID 5 array, where should I install OS (do I have to create partitions and do OS installation on that?)

I am sorry, if my questions surprising you. Because I am new to this kind of stuffs. Thank you,

 

[Ijack]

1. Correct. A hot spare is just a disk that sits there doing nothing until another disk in the array fails. Then it automatically takes the place of that failed disk (and you would get some sort of message telling you thatbhad happened). So the array continues as normal and is still protected - another disk failure would not be fatal (but a third would). Without a hot spare a disk failure leaves the array working but unprotected against a second failure.

2. The array appears as a single physical drive. So you can partition it as you would a single drive.