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FC60 with No Raid?

Marc Workman
Occasional Visitor

FC60 with No Raid?

We have 2 FC60 disk arrays with 3 trays each and 4 - 36 GB drives in each tray. This gives us approximately 862 GB of raw space. These arrays are intended to be used by an Informix database. My Informix DBA tells me that we want to let Informix handle the mirroring so we do not want any raid since this will be overkill. Can we turn off raid on the FC60s? And if so, how? If it can't be turned off, does raid 5 give us the least overhead? Based on my calculation, using raid 5 and Informix mirroring would only give us about 290 GB of usable space. Any suggestions?
4 REPLIES
Dave Wherry
Esteemed Contributor

Re: FC60 with No Raid?

I have to disagree with your DBA. If you are going to let Informix handle the mirroring, that means the engine has to send 2 writes and wait for those to be committed each time it has a write. Do 1 write, keep that load off of the host and let the array handle the redundancy.

Something seems strange about your calculations. It shows you will only have about 33% usable space out of your raw space. That's too much overhead.
I haven't worked with an FC60, I have a couple of FC30's and I assume they work the same way.
You have 12 disks in each of your arrays. If you have a hot spare you lose 1 disk, 36GB per array. That leaves 11 disks per array, 396GB. That's 792GB total.
There will be waste, or overhead depending on how you partition the disks. I can't see 502GB of overhead.
It sounds like you are creating several small LUNs and maybe counting the mirrors. That's a lot of wasted disk. I would go with larger LUNs and forget the mirrors.
Byron Myers
Trusted Contributor

Re: FC60 with No Raid?

HP has informed me that FC60 configured as JBOD is NOT supported. I tried doing the exact same thing on my FC60 (for Informix too). I configured the array for JBOD (not supported) by setting dip switch 2 on the BCC to "Stand-Alone" mode (1). The problem I ran into was that LUN 0 on an FC60 MUST be RAID - this contradicts the dip switch setting above.

As far as getting the most usable space (at the cost of performance), Raid 5 is best. For each FC60, you should configure 4 RAID 5 luns - each with 3 disks. If you want a spare, another disk will be needed. This will give you 8X36GB usable per FC60 (4X36GB overhead).

Since the FC60 conroller will be handling the I/O, you will encounter a performance decrease if you let Informix mirror its data.
DBA's always want to control the disk, but with arrays they can't. I suggest a little education here for your DBA(s).


If you can focus your eyes far and straight enough ahead of yourself, you can see the back of your head.
Bill McNAMARA_1
Honored Contributor

Re: FC60 with No Raid?

Why bother?
But if you really want to do that buy a few
LVD SCSI card and use your SC10 enclosures
as a JBOD and through your FC60 raid
controller away.

Your raid 5 storage does seems a bit low.
Make sure that all disk mechs are the same
size in each LUN. (Just like your FC30!)

Later,
Bill
It works for me (tm)
KwangHee Yi
Advisor

Re: FC60 with No Raid?

You cannot turn off RAID on the FC60 disk. If you really want it, connect disk encloures(trays) to the system. In that case, you should use SCSI interfaces and Fibre channel contoller is not useful any more.