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JarryG
Expert
Expert

ESXi 5.1 loosing RAM?

Hi Community, I have this strange problem (or feature, for which I did not find any explanation):

The first "server" (virtual computer) I tested with ESXi had 2GB RAM, and after booting I have seen "2 GiB Memory".

Later I installed ESXi on some real workstation, with 16GB RAM, and ESXi reported "16 GiB Memory".

Now I'm testing ESXi on server with 32GB RAM, and after booting ESXi says "31.7 GiB Memory".

Why ESXi lost ~300MB of RAM?

If I had seen the same with all ESXi-installation (300MB less than real RAM capacity), I'd think it is reserved for hypervisor itself and therefore substracted from total value. But why only in scenario with 32GB RAM? BIOS reports full 32GB and I see the same value during POST (power-on self test). I booted linux (live-cd), it reports full 32GB too. HW (cpu, mobo, ram) is on compatibility list, so it should be fully supported...

_____________________________________________ If you found my answer useful please do *not* mark it as "correct" or "helpful". It is hard to pretend being noob with all those points! :winking_face:
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lakshya32
Enthusiast
Enthusiast

Hi JarryG

Welcome to the forums.

what comes to mind is ESX service console typically uses 272MB and the VMkernel uses a around 50 mb of memory.

May be due to that its reflecting 300 less memory .

"When you fail to plan, you plan to fail."
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elgreco81
Expert
Expert

Hi,

Esxi doesn't have a service console. Could you run esxtop tosee what's in there?

Regards,

elgreco81

Please remember to mark as answered this question if you think it is and to reward the persons who helped you giving them the available points accordingly. IT blog in Spanish - http://chubascos.wordpress.com
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JarryG
Expert
Expert

I do not know what exactly I should look for, esxtop reports just usual things (with "m" activated):

5:57:57pm up 1 min, 303 worlds, 0 VMs, 0 vCPUs; MEM overcommit avg: 0.00, 0.00, 0.00
PMEM  /MB: 32490   total:   959     vmk,    84 other,  31447 free
VMKMEM/MB: 32331 managed:   937 minfree,  3205 rsvd,  29125 ursvd,  high state
PSHARE/MB:    13  shared,    13  common:     0 saving
SWAP  /MB:     0    curr,     0 rclmtgt:                 0.00 r/s,   0.00 w/s
ZIP   /MB:     0  zipped,     0   saved
MEMCTL/MB:     0    curr,     0  target,     0 max

     GID NAME               MEMSZ    GRANT    SZTGT     TCHD   TCHD_W    SWCUR
    1692 hostd.4973         50.52    36.30    39.93     7.38     7.38     0.00
    2294 vpxa.5291          21.20    13.16    14.47     2.66     2.66     0.00
     844 vobd.4505          12.28     1.32     1.45     1.33     1.33     0.00

<etc>

But I made a few tests. There are 4 memory modules, each 8GB, marked A1, A2, B1, B2.

I removed A2 module, bios reports 24GB, ESXi (welcome-screen) says 23.7 GiB.

I put back A2 and removed B2, Bios repots 24 GB, ESXi says 23.7 GiB.

I removed both A2 and B2, bios reports 16GB, ESXi says 15.7 GiB.

I removed A2, B1 and B2, bios reports 8GB, ESXi says 7.7 GiB.

I tested every memory module as single in A1, always bios sees 8GB, ESXi only 7.7 GiB.

It seems to me ESXi "lost" ~300MB, no matter how many (or which) RAM-modules I have!

BTW it is unbuffered ecc ddr3-1600, exactly as required and compatible with my motherboard (Intel S1200BTL).

There are only two memory-related options in bios:

Maximize Memory below 4GB: disabled (bios says: enable only for OS without PAE)

Memory Mapped I/O above 4GB: disabled

Should I change something?

_____________________________________________ If you found my answer useful please do *not* mark it as "correct" or "helpful". It is hard to pretend being noob with all those points! :winking_face:
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