Hi there, Long time Linux user here, very familiar with tools for system administration but somewhat stumped by the behaviour of a system installed by me about six years ago at a local farm. It's an old Intel 'NUC' like this one:
https://ark.intel.com/content/www/us/en/ark/products/78577/intel-nuc-kit-de3815tykhe.html It has an Intel E3815 CPU (~1.5GHz), 8GBytes of RAM, 250Gbyte SSD. As luck would have it there's a second system on the site, identical save for a 1Tbyte laptop-style spinning disc, but I'll come to that later. The 'problem' box is used for all the usual stuff (email and document processing, scanning, printing etc.) plus banking, online orders from suppliers, security monitoring (some custom Perl scripts and 'motion', using a variety of cameras), and United Kingdom VAT returns through a combination of a Windows 7 VM under VirtualBox (fired up quarterly - to power some Microsoft Office scripts and Microsoft's browser - for what should be ten minutes but what in reality, through no fault of the computer, is usually nearer a day). Remote management is by VPN, I use Nagios/Icinga and Smokeping for routine monitoring, plus shell access for any ad-hoc stuff. The users at the farm don't have root; they don't even know what it is and don't want to. Running Debian 'Jessie', until now it has performed very acceptably. Not of course the quickest box you've ever seen but perfectly capable of carrying the load. I left moving to a later edition of Debian for as long as I felt comfortable because I don't like change for the sake of change and because of misgivings shortly to be more than justified about the likely result. Last week, because Buster's now been out for a year, I thought it's time. Big mistake. As the box was still running Jessie I had to do the move in two bites. First move from Jessie to Stretch, then from Stretch to Buster. The entire process was a bit long-winded and spread over a couple of days, but seemed to go smoothly enough. Immediately, the users started to complain about performance. Not just a small reduction, but the sort of thing that makes the whole system completely unusable. My estimate after looking at the response on the desktop is several hundred times slower than normal for this box. If you click on a message in the list of messages presented by the mail client, instead of seeing the message in under a second you can go and have a coffee break and still get back before it's shown on the screen. The usual admin tools like top, atop, sysstat, sar, free, don't give me much to go on. The system load averages are elevated to an extent, but 'top' doesn't show any particular processes hogging CPU. IO wait times are if anything less on the problem machine than they are on the box which is still running Jessie and disc accesses aren't excessive. Many hours of searching later I've drawn a blank. One suggestion was that the xserver-xorg-video-intel package might be a problem but I've uninstalled that with no obvious effect. I first disabled, and later removed, AppArmor - same result. It's as if the box has just decided to put its feet up. To get the farm office back up and running I took the office manager's home directory from the problem machine, dropped it onto the other NUC which still runs Jessie, and replaced the problem box with that. The office could at least then pay the wages. It might be worth noting that it took about two and a quarter hours to gzip that home directory (about four gigabytes) on the problem machine (Buster), and about five minutes to gunzip it on the Jessie box. What can possibly cause such a drastic reduction in performance? -- 73, Ged.
