Re: Is there a limit on the count of the exported devices?
On Sat, Jan 04, 2020 at 09:20:40PM +0100, Vladimir Zhelezarov wrote:
> Hi,
>
> independent of the size of the combined block device, I am unable to use more
> than 1018 devices with the "-m" option in nbd-server. So for example:
>
>
> for i in {0..1999}; do truncate -s 1M mm.$i; done
> sudo nbd-server -C /dev/null localhost@33333 -m /home/user/nbd/mm
> sudo nbd-client localhost 33333 /dev/nbd0
>
>
> Then it says:
>
> Negotiation: ..size = 1018MB
> bs=1024, sz=1067450368 bytes
>
> which can also be confirmed by mounting /dev/nbd0.
>
>
> Another example with 5000 files of 500K gives:
>
> Negotiation: ..size = 497MB
> bs=1024, sz=521216000 bytes
>
> which gives the same 521216000/1024/500 = 1018 used files.
>
>
> The same happens when using different sizes or combinations of sizes and
> file-counts. I am using nbd 3.20 on x64 Ubuntu 18.04. Using a configuration
> file makes no difference. Different hardware with the same OS and nbd version
> neither.
>
>
> Can someone give me some pointers?
As you found out in the mean time, nbd-server doesn't impose a limit,
but the OS might.
The limits can be configured on Linux with "sysctl -w
fs.file-max=<number>", where you replace <number> by the number of files
you need (plus a small margin).
Thanks,
--
To the thief who stole my anti-depressants: I hope you're happy
-- seen somewhere on the Internet on a photo of a billboard
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