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I'm designing lab with a Dell M1000e and 3 M620 blade servers. Each blade server has 2 local HDD of 130GB on RAID 1.

My first attempt is to install ESXi in an SD card or USB key so my local storage is empty.

The question, what's the purpose of local HDD in this blade server? I mean, I have a SAN network with XX TB so this 130Gb looks ridiculous. Apart from installing ESXi to the local drive instead of the SD card, is there another use for this local storage?

EDIT: I just inherited the devices from previous tech guys. I just trying to understand why they bought local storage.

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    If you don't think you need those disks, why did you buy them? – Sven Jul 16 '17 at 11:26
  • I inherited the devices from the previous tech guys. I just trying to understand if it can be useful for today virtualized data center. I will clarify it in the original question. – KorXo Jul 16 '17 at 12:22
  • You could use it for swap or ephemeral storage, for swap disks might be too slow and I think for ESX shared storage is better managed in the SAN, so probably not terrible useful (not sure about temp usage of ESX, with OpenStack local disks do make some sense on the compute nodes). – eckes Jul 16 '17 at 14:23
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SD card OS installation for virtualization hypervisor hosts is common, but at scale, it's less reliable than using simple RAID 1 on regular disks or SSD.

See: What happens when the USB key or SD card I've installed VMware ESXi on fails?

I prefer a pair of low cost SSDs (120GB) or a pair of 300GB or 900GB SAS disks for this purpose. The advantage is having a bit of scratch local space that I can bring online as a VMFS volume, and less worry about needing to recover a host after an SDHC or USB media failure.

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Obvious: OS and booting. Having local boot drives can make sense. I also prefer the virtualization layer to not be dependent on an external storage.

It is so common that for example SuperMicro has made super small SSD that look like a small USB stick and fit on a local SATA port (term SATA DOM - Disc On Module).

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I see following reasons to use local HDDs:

  • (I am going with) Windows Server
  • (I need some) redundancy (RAID 1)
  • (and) performance (in case of RAID 1 SSD, boot is faster than SATADOM or Flash)
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Installing the hypervisor on local storage such as you have (small drives configured in RAID 1) was and still is a very common practice.

In short, nothing to see here.

  • Not sure why do you want to waste 2 SATA / SAS ports and a corresponding pair of disk bays for your OS? USB stick (Hyper-V) / mirrored SD cards (ESXi & others) work just fine. – BaronSamedi1958 Jul 22 '17 at 6:22
  • I'm just saying that it's a fairly common thing. – joeqwerty Jul 22 '17 at 10:56

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