I have noticed significant storage amplification for my zvols; that could very
well be the reason. I would like to know more about why it happens.
Since the volblocksize is 512 bytes, I certainly expect extra cpu overhead (and
maybe an extra 1k or so worth of checksums for each 128k block in the vm), but
how do you get a 10X expansion in stored data?
What is the recommended zvol block size for a FreeBSD/ZFS guest? Perhaps 4k, to
match the most common mass storage sector size?
- .Dustin
> On Dec 1, 2017, at 9:18 PM, K. Macy <[email protected]> wrote:
>
> One thing to watch out for with chyves if your virtual disk is more
> than 20G is the fact that it uses 512 byte blocks for the zvols it
> creates. I ended up using up 1.4TB only half filling up a 250G zvol.
> Chyves is quick and easy, but it's not exactly production ready.
>
> -M
>
>
>
>> On Thu, Nov 30, 2017 at 3:15 PM, Dustin Wenz <[email protected]> wrote:
>> I'm using chyves on FreeBSD 11.1 RELEASE to manage a few VMs (guest OS is
>> also FreeBSD 11.1). Their sole purpose is to house some medium-sized
>> Postgres databases (100-200GB). The host system has 64GB of real memory and
>> 112GB of swap. I have configured each guest to only use 16GB of memory, yet
>> while doing my initial database imports in the VMs, bhyve will quickly grow
>> to use all available system memory and then be killed by the kernel:
>>
>> kernel: swap_pager: I/O error - pageout failed; blkno 1735,size 4096,
>> error 12
>> kernel: swap_pager: I/O error - pageout failed; blkno 1610,size 4096,
>> error 12
>> kernel: swap_pager: I/O error - pageout failed; blkno 1763,size 4096,
>> error 12
>> kernel: pid 41123 (bhyve), uid 0, was killed: out of swap space
>>
>> The OOM condition seems related to doing moderate IO within the VM, though
>> nothing within the VM itself shows high memory usage. This is the chyves
>> config for one of them:
>>
>> bargs -A -H -P -S
>> bhyve_disk_type virtio-blk
>> bhyve_net_type virtio-net
>> bhyveload_flags
>> chyves_guest_version 0300
>> cpu 4
>> creation Created on Mon Oct 23 16:17:04 CDT 2017 by
>> chyves v0.2.0 2016/09/11 using __create()
>> loader bhyveload
>> net_ifaces tap51
>> os default
>> ram 16G
>> rcboot 0
>> revert_to_snapshot
>> revert_to_snapshot_method off
>> serial nmdm51
>> template no
>> uuid 8495a130-b837-11e7-b092-0025909a8b56
>>
>>
>> I've also tried using different bhyve_disk_types, with no improvement. How
>> is it that bhyve can use far more memory that I'm specifying?
>>
>> - .Dustin
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