Friday, July 9, 2010

Got a RAID? Are you sure?

Nothing more amusing then when you take the cover off a server, clear all the debris and grey "fluff" out of the box to add some RAM to a machine and find 2 hard drives where there should be 3.

Well, I say should be, but let's put it a different way, I was told it was a RAID drives and I presumed RAID 5, evidently the hardware builder did not or the box was never ordered with more than 2 drives.

Given the box was running Lotus Domino apps it didn't need huge disk space like a mail server, but still, mirrored drives?

Yes, the person built the best with what they had, but they left one problem. What happens when one of the 2 drives fails. Yes, you lose the server until someone can fix it, if they can. Hope you had backups.

So if you are a new admin or even an experienced one and end up in a new environment it's always a good idea to get an inventory of what is in the servers. You never know when one of them might go belly up on you, like in the middle of a holiday weekend perhaps.


  1. Mirrored drives are much better at Domino's random I/O than RAID 5 and it is no less fault tolerant than RAID 5. If you loose a drive with either RAID level, you are still functioning. It is documented that RAID 5 is not recommended, especially for a busy mail server. Now, that's not to say that it should not be used. For an apps server it is OK. Actually, I've found it to be very common since RAID 5 is obviously a more efficient use of drives. But it should be used with Transactional logging to help with write performance, on a separate array, of course. Domino drive array configurations are the most important aspect of a well performing server and the most taken for granted.

  2. I agree with @1 I avoid RAID 5 as best I can. I've been mirroring for years. The most recent servers I've spec'd have 3 sets of RAID 1 drives, 1 for O/S, 1 for Transaction logs and 1 for Domino.

  3. And if you can afford it, for the drives with the .NSF on it, RAID 10 ideal? With the transaction logs on RAID 1, minimally on their own pair of spindles, ideally on their own controller, same for the OS itself?

  4. You are all correct in your discussions.
    This was not about the RAID as much as never presume you know what is on the inside until you see it.

    I presumed a RAID5 because it was not a mail server(and the person who set it up was just a hardware vendor) and more common at the time.
    Now to rebuild it I can only use what we have with new drives.(we have new servers on order).
    Trans log will go by itself of course for now. As will the OS.
    But we are limited to 4 drives inside the box(baby tower) and don't want externals.
    Money will go into thew new servers.