VMware ESXi Local Disks Showing as Remote

A little over a month ago, I was installing VMware ESXi on a Cisco UCS blade and noticed something odd during the installation. I posted a tweet about the incident. Here’s the text of the tweet in case the link above stops working:

Interesting…this #UCS blade has local disks but all disks are showing as remote during #ESXi install. Odd…

Several people responded, indicating they’d run into similar situations. No one—at least, not that I recall—was able to tell me why this was occurring, only that they’d seen it happen before. And it wasn’t just limited to Cisco UCS blades; a few people posted that they’d seen the behavior with other hardware, too.

This morning, I think I found the answer. While reading this post about scratch partition best practices on VMware ESXi Chronicles, I clicked through to a VMware KB article referenced in the post. The KB article discussed all the various ways to set the persistent scratch location for ESXi. (Good article, by the way. Here’s a link.)

What really caught my attention, though, was a little blurb at the bottom of the KB article in reference to examples where scratch space may not be automatically defined on persistent storage. Check this out (emphasis mine):

2.  ESXi deployed in a Boot from SAN configuration or to a SAS device. A Boot from SAN or SAS LUN is considered Remote, and could potentially be shared among multiple ESXi hosts. Remote devices are not used for scratch to avoid collisions between multiple ESXi hosts.

There’s the answer: although these drives are physically inside the server and are local to the server, they are considered remote during the VMware ESXi installation because they are SAS drives. Mystery solved!

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10 comments

  1. Forbes Guthrie’s avatar

    Hi Scott,
    That’s funny because I wrote an article about a similar issue last night (prompted by the same great KB).
    http://www.vreference.com/2011/04/26/esxi-disks-must-be-considered-local-for-scratch-to-be-created/
    You’ll notice that for some servers (HP in my case), the disks are considered remote, even though they are indeed local and not boot from SAN.
    Cheers,
    Forbes.

  2. Aaron Delp’s avatar

    Just reached out to you on Twitter but if I think about the bigger picture for a second, that means that ALL Cisco UCS installations need to have scratch space created because they will either be Boot From San (considered remote) or SAS (considered remote). Am I missing something?

    Thanks!

    -Aaron

  3. slowe’s avatar

    Forbes,

    I guess they say great minds think alike! Great article.

    Aaron,

    You are indeed correct, although there was some confusion on Twitter about local SSDs, which are SATA drives. I don’t yet know if those will be considered remote or not, or if the fact that they are SSD will cause ESXi to not create persistent scratch storage on them (see the previous bullet point in that KB article). Either way, it’s a good thing to point out. I’ll let you take that point back to Vblock Product Management. :-)

  4. PiroNet’s avatar

    Also to note that if the scratch partition has to go ramdisk, only a 512MB partition (and not 4GB) will be created. 512MB taken out of the server’s available physical memory.
    Cheers,
    Didier

  5. Sid’s avatar

    We recently went through this issue with HP BL685 G7′s, there is a work around available, I will find out what that is and post the details.

  6. Sid’s avatar

    The work around is to the kickstart script to manually create the scratch partition. My colleagues went back and forth with support on this issue and I believe it is being worked on.

  7. Anders Mikkelsen’s avatar

    Hi Sid,
    Can you supply me with some more data on the solution?
    I have the same problem and are stuck….

    A. Mikkelsen

  8. bawaa’s avatar

    Hi,

    Great article,
    Hp xw9400, only 1 sata disk inside the box and its considered remote too, problem is that I am installing on a USB, install finishes fine, but it won’t boot esx via USB. Esx 5.0 is the version. I have tried disabling HDD in the bios but still it won’t detect esx installed on a USB.however other USB boots fine and I can install windows with it or boot ubuntu with it…. Any ideas ??

    Thanks

  9. schubacca’s avatar

    Haha, had the same issue here with some SAS drives in my HP DL380p Gen8 machine. Mystery installed indeed ^_^

    Thanks for the help!

  10. ltpmy’s avatar

    hi schubacca, how you solve it or use as remote storage, please let me know

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