On 08/10/2018 03:02 PM, Kelly Dean wrote:
Has anybody else used both Qubes 3.2 and 4.0 on a system with a HD, not SSD?
Have you noticed the disk thrashing to be far worse under 4.0? I suspect it
might have something to do with the new use of LVM combining snapshots with
thin provisioning.
The problem seems to be triggered by individual qubes doing ordinary bursts of
disk access, such as loading a program or accessing swap, which would normally
take just a few seconds on Qubes 3.2, but dom0 then massively multiplies that
I/O on Qubes 4.0, leading to disk thrashing that drags on for minutes at a
time, and in some cases, more than an hour.
iotop in dom0 says the thrashing procs are e.g. [21.xvda-0] and [21.xvda-1],
reading the disk at rates ranging from 10 to 50 MBps (max throughput of the
disk is about 100). At this rate, for how prolonged the thrashing is, it could
have read and re-read the entire virtual disk multiple times over, so there's
something extremely inefficient going on.
Is there any solution other than installing a SSD? I'd prefer not to have to
add hardware to solve a software performance regression.
I really don't know if LVM or Ext4 have an SSD/HDD mode, but Btrfs does.
The HDD mode avoids some thrashing.
Also, I remember installing a 4.0 release candidate on an external HDD
and didn't note unusual thrashing at the time.
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