On March 28, 2020 11:03:54 AM GMT+02:00, Gianluca Cecchi <gianluca.cecchi@gmail.com> wrote:
On Sat, Mar 28, 2020 at 8:39 AM Strahil Nikolov <hunter86_bg@yahoo.com> wrote:
On March 28, 2020 3:21:45 AM GMT+02:00, Gianluca Cecchi < gianluca.cecchi@gmail.com> wrote:
[snip]
Actually it only happened with empty disk (thin provisioned) and sudden
high I/O during the initial phase of install of the OS; it didn't happened then during normal operaton (even with 600MB/s of throughput).
[snip]
Hi Gianluca,
Is it happening to machines with preallocated disks or on machines with thin disks ?
Best Regards, Strahil Nikolov
thin provisioned. But as I have tro create many VMs with 120Gb of disk size of which probably only a part during time will be allocated, it would be unfeasible to make them all preallocated. I learned that thin is not good for block based storage domains and heavy I/O, but I would hope that it is not the same with file based storage domains... Thanks, Gianluca
This is normal - gluster cannot allocate fast enough the needed shards (due to high IO), so the qemu pauses the VM until storage is available again . You can think about VDO (with deduplication ) as a PV for the Thin LVM and this way you can preallocate your VMs , while saving space (deduplication, zero-block elimination and even compression). Of course, VDO will reduce performance (unless you have battery-backed write cache and compression is disabled), but tbe benefits will be alot more. Another approach is to increase the shard size - so gluster will create fewer shards, but allocation on disk will be higher. Best Regards, Strahil Nikolov