September 2021 – .pQd's log

booting KVM VM from an iso image

2021-09-252021-12-25 by .pQd

let’s say you have a vm, maybe with debian. and that vm stopped booting, maybe because of grub corruption. what do you do? add under devices – for pc-i440fx arch: and for pc-q35-3.1: then in the os section change boot from dev=’hd’ to dev=’cdrom’: then also – this article describes how to go back from ... Read More

20x performance difference between two VMs running the same version of Elastic opendistro

2021-09-11 by .pQd

i’ve just spent way too much time trying to figure out why the same query run on one VM with elastic 0.1s while on another – 2s. both VMs were running on the same physical server, had the same amount of cores allocated. i’ve finally found it – there was a tiny difference in amount ... Read More

ClickHouse – dictionary with string keys

2021-09-032022-02-24 by .pQd

i wanted to create a clickhouse dictionary that used String as a key, not an int. docs mention here: “A composite key can consist of a single element. This makes it possible to use a string as the key, for instance”. I’ve been trying this and failed few times. creation worked but i could not ... Read More