Why it’s so important and desirable to have configured graceful shutdown for DB servers and hypervisors.
From my experience it’s completely nonsense that almost all Mongolian companies are so neglect to UPS issues. Servers should be mandatory configured for graceful shutdown by USB or PCNS cards. Otherwise for long black outs there is no difference between UPS backed or not RACK systems – servers will be just cut off mercilessly damaging database files, file system, boot sectors, virtual hard disks and so on.
In case of proper configuration and on battery event SmartUPS (or very few BackuUPS) will send by USB cable (or thru PCNS card via network) signal to own installed agent to graceful shutdown computer/server – as if you yourself shutdown computer – all programs/processes/services will be closed in normal way, all DB files will be unlocked by running/stopping services, all cache operations will be finished and so on.
If you ignore a such configuration then earlier or sooner your servers may stop booting due to corrupted boot sector, boot files, file system or partition damages; large files (usually it’s vhd, vmdk containers or DB mdf files and so on) usually intensively used and therefore cached mainly in RAM becomes damaged; if RAID battery long time nobody checked then all data in 512Mb or 1gb battery backed RAM cache will be lost. Or if your server suddenly restart or shutdown in the middle of intensive deep system changes (for example Windows Update) your system can stop working properly and so on. Other hidden problem is sequence of blackouts in short unpredictable time when properly shutdowned by UPS servers are improperly configured to start on low charged UPS (not ready for series of next blackouts). Or another wrong common misconfiguration is when hypervisor servers are not configured to shutdown/(start in safe sequence – for example Exchange and Lync only after start of AD DC hosts) properly own guest OS and so on.
In first glance all these configurations look very easy and obvious. But for small business it’s very common to have even poorly designed, incorrectly chosen electric equipment. In Mongolia there is no mandatory electric standards, so we have a zoo of jacks from all around the world which leads to very bad electric contacts, overloaded and burnt power expanders; cheap Chinese jacks and wall outlets bought and installed without checking metal made of (Neodymium magnet from damaged HDD is the easiest way to check a such equipment). So UPS in server room or RACK in our situation should act taking into account also 1) different power standard types of jacks, 2) aluminium contacts , 3) twisted copper, aluminium contacts 4) bad melting plastics of jacks and so on (if not mentioning that UPS shouldn’t be power source for laser printers, consumer level Air Conditioners in our server rooms should be powered from other electric phase).