global hot spare drive

Posted on 2014-08-28
Last Modified: 2014-09-03

Dell is building new domain controller for me. I'd like have global host spare drive in this server.


Server power edge r620
RAID 1 (OS) - 2x 600 GB
RAID 5 (DATA) 4 x 600 GB

What single drive I should use as global hot spare (what size) and how should be configured (where connected, any raid should be on it ?)

I have pretty hard time to get correct answer from DELL.
thank you,

Question by:henryk123
    LVL 32

    Accepted Solution

    It should not be a hard question for the sales guys at Dell to answer.

    In order for a disk to be a hot-spare, it must be AT LEAST as large AND the same type (SAS/SATA) as the disks in the array(s) it will protect.

    Both of your RAID arrays use 600GB SAS disks, so your hot-spare must be a 600GB SAS disk.  It can be larger, but I'm not sure why you would get a larger one - there is no advantage.

    To utilize a hot-spare, you simply assign that role to a disk that is not currently being used in an array:

    Global HS:  Will protect both of your arrays.  If a disk fails from either array, the HS will rebuild in its place.

    Dedicated HS:  Will protect ONE array - whichever array you assign the hot-spare to.  If you assign the HS as dedicated to the RAID 1, and a disk fails from the RAID 5, then the HS will NOT rebuild in the failed disk's place - ONLY if a RAID 1 disk fails.
    LVL 46

    Assisted Solution

    The global hot spare needs to be >= the capacity of the largest disk drive you have in an array with the same technology. If largest SAS disk you have is 1TB then it needs to be >= 1TB.

    If you mix & match SAS & SATA then you will need a SAS hot spare and a SATA hot spare.
    LVL 3

    Assisted Solution

    Hi Henryk123,

    Per your current config.  Your primary boot drive containing your OS is Raid 1 meaning they are mirrored.  So, every time something is written to disk 1 the same is written to disk 2. Fast and contains mirror backup.

    Your Data volume is Raid 5 which in this case is not really the best situation only having 4 drives.  The minimum drives for Raid 5 is 3 and you can have a hot spare with it or no hot spare at all.  So, if none of these drives are hot spares and a drive fails you stay up but loose a 2nd drive you  will loose all the data.

    That is why I would have used all drives in a Raid 5 array with one drive as a hot spare.  Remember with Raid 5 its N-1 with one drive being used for parity.

    Featured Post

    How to run any project with ease

    Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
    - Combine task lists, docs, spreadsheets, and chat in one
    - View and edit from mobile/offline
    - Cut down on emails

    Join & Write a Comment

    The 6120xp switches seem to have a bug when you create a fiber port channel when you have a UCS fabric interconnects talking to them.  If you follow the Cisco guide for the UCS, the FC Port channel will never come up and it will say that there are n…
    Hyper-convergence systems have taken the IT world by storm and have quickly started to change our point of view of how the data center should and could be architected. In this article, I’ll explain the benefits of employing a hyper-converged system …
    In this sixth video of the Xpdf series, we discuss and demonstrate the PDFtoPNG utility, which converts a multi-page PDF file to separate color, grayscale, or monochrome PNG files, creating one PNG file for each page in the PDF. It does this via a c…
    Illustrator's Shape Builder tool will let you combine shapes visually and interactively. This video shows the Mac version, but the tool works the same way in Windows. To follow along with this video, you can draw your own shapes or download the file…

    734 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    23 Experts available now in Live!

    Get 1:1 Help Now