Array Configuration Suggestions??

[jludwig1]

Hello,

After talking with dell multiple times on this issue all I get is different answers. So hopfully I will get to some consensus on here.

I have a Dell 4400 with a PERC3/di controller. I have 3 physical disks 36gig each for my exchange server. We we call these disk0, 1, and 2.

The Perc3/di allows you to create more than one RAID level on each disk so this is how they are configured right now. Keep in mind the goal here was to create as much hardware fault tolerance as possible while keeping the System partition on a hardware Mirror and the Data on Raid 5, but only having 3 total disks.

RAID 1 - Mirror - used for system (Drive C: in win)
10gig of disk0 and disk1

RAID 0-STRIPE-used for swap space(drive G: in win)
10gig of disk2

RAID 5- used for data (drive F: in windows)
The remaining 26gig of disk 0, 1, and 2

When I have had a disk fail , say disk 0 in this senerio I have called Dell and they have told me that it was PHYSICALLY IMPOSSIBLE to have this setup. Well as you can see I have been running with this setup for 2 years now. Also they state that this is a BAD way of setting this up becuase there are too many different RAID levels on each disk.

My question is 3fold:
1.) Is this not a good idea to config this way?
2.) Would a better way to to this make all the disks RAID 5 and just partition the space for my drives, then I would only be able to recover if just one disk fails?
3.) I couldnt use the Mirror on Disk1 becuase the Perc Array configuration was GONE! I have had this happen multiple times, does anyone else ever had Dells Perc3/di RAID configuration just get blown out? One time I had to reset the RAID battery, memory and pull out the RAID key!!! Is this normal???

Thanks in advace.
Jason

 

[technome]

It is interesting you were able to create this, but never in my dreams would I have such a setup.
Innovative, but extremely dangerous.

Set the entire array as raid 5. Re install windows, one partition for the OS system and one for the data


Basically having raid 0 configured in this group of disks brings your entire setup down to a level safety level of raid 0, being NO redundancy at all.

I understand your reasoning of the setup, I find it interesting that it was allowed by the adapter in the first place. Having the mirror or raid 5 provided no safety what so ever, losing the raid 0 kills everything because the raid adapter fails or offlines disks, not individual array sets.

As a suggestion, if this is a production server forget you ever learned about raid 0. How this was ever became a raid classification is beyond me. This belong to in the league with Microsoft's belief you can create an array of 32 mixed environment disks (mfm, ide, scsi) and have it last for more than 60 seconds; haven't seen it in a while, but it was in the NT books.

 

[DanZeMan]

You're two disks short!!
I would recommend that you mirror for the OS, and create RAID5 for your Data (exchange).
Maximum safety, and maximum performance.
We resist any server config that has less than four disks - which at the very least gives you two mirrors.

 

[Gabby75]

Agreed; dangerous configuration, didnt even think you could do it. Never have more then 1 Raid level on any spindle. For example your G: drive (called Raid 0 but actually JBOD (just one disk) has no resilience at all. Lose disk 2 and G: is gone.

So either 1) Raid-5 across all 3 disks giving 72GB usable (partition as required) or 2) Mirror 2 disks, and make one a hotswap.

As you have only 3 disks, recommend the first one, but be aware that loss of 1 disk will you leave you in a degraded and less perfoamant state until disk is replaced.

 

[NickFerrar]

You can do it with software RAID but as others said I didn't think you could do it on PERC's, you wouldn't want to for sure.