hardware interview questions

Top 15 hardware interview questions

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How to find out details about hardware on the Linux machine?

-i.e - how to get a full list of hardware components in command line (on a machine with no window system)

Thank you.

Source: (StackOverflow)

Does a 500 watt power supply always use 500 watts of electricity? [closed]

Does a 500 watt power supply always pull 500 watts? Or does it depend on the load being placed on the computer?

It's a n00b hardware question. I'm trying to figure out how much it costs to run my compuer without buying a meter that actually measures power usage.

Source: (StackOverflow)

How is fire spread in server rooms and datacenters?

Every now and then I read that a severe fire has happened in some datacenter, lots of equipment has been damaged and customers have gone offline. Now I wonder what is there to support and spread fire?

I mean walls in a server room usually have little or no finish. Racks are made of metal. Almost all units have metal cases. Cables have (or at least should have) insulation of materials that don't spread fire.

What is spreading fire in a server room or datacenter?

Source: (StackOverflow)

What should I pay attention to when I'm buying a network switch?

Since I'm not a hardware expert, I don't know what features make a network switch a good network switch. What should I pay attention, when I'm comparing the different models from different vendors?

Source: (StackOverflow)

Is UPS worthwhile for non-production equipment? [closed]

Over the years, I've had to throw away a quite a few bits of computing equipment (and the like):

  • Several ADSL routers with odd symptoms (losing wireless connections, losing wired connections, DHCP failures, DNS symptoms etc)
  • Two PVRs spontaneously rebooting and corrupting themselves (despite the best efforts of the community to diagnose and help)
  • One external hard disk still claiming to function, but corrupting data
  • One hard disk as part of a NAS raid array "going bad" (as far as the NAS was concerned)

(This is in addition to various laptops and printers dying in ways unrelated to this question.)

Obviously it'll be impossible to tell for sure from such a small amount of information, but might these be related to power issues? I don't currently have a UPS for any of this equipment. Everything on surge-protected gang sockets, but there's nothing to smooth a power cut.

Is home UPS really viable and useful? I know there are some reasonably cheap UPSes on the market, but I don't know how useful they really are. I'm not interested in keeping my home network actually running during a power cut, but I'd like it to power down a bit more gracefully if the current situation is putting my hardware in jeopardy.

Source: (StackOverflow)

How to extinguish a small fire in a server rack to minimize damage to surrounding equipment?

Suppose I have a rack with several servers and other stuff. One of servers overheats severely and either starts smoking or catches fire while there's a serviceman nearby.

If anything similar happens in an apartment and there's a fire extinguisher nearby using the latter promptly often lets extinguish the fire very fast but in case of server rack improper extinguishing may lead to unneeded extra damage to surrounding equipment.

To clarify, I'm talking about a really small fire that one can try to extinguish without risking their life - like grab a nearby extinguisher, discharge it and get the fire extinguished in say ten fifteen seconds.

What's the strategy to extinguish a small local fire in a server rack? What type of extinguisher is to be used? How to minimize damage to surrounding equipment?

Source: (StackOverflow)

Something is burning in the server room; how can I quickly identify what it is?

The other day, we notice a terrible burning smell coming out of the server room. Long story short, it ended up being one of the battery modules that was burning up in the UPS unit, but it took a good couple of hours before we were able to figure it out. The main reason we were able to figure it out is that the UPS display finally showed that the module needed to be replaced.

Here was the problem: the whole room was filled with the smell. Doing a sniff test was very difficult because the smell had infiltrated everything (not to mention it made us light headed). We almost mistakenly took our production database server down because it's where the smell was the strongest. The vitals appeared to be ok (CPU temps showed 60 degrees C, and fan speeds ok), but we weren't sure. It just so happened that the battery module that burnt up was about the same height as the server on the rack and only 3 ft away. Had this been a real emergency, we would have failed miserably.

Realistically, the chances that actual server hardware is burning up is a fairly rare occurrence and most of the time we'll be looking at the UPS the culprit. But with several racks with several pieces of equipment, it can quickly become a guessing game. How does one quickly and accurately determine what piece of equipment is actually burning up? I realize this question is highly dependent on the environment variables such as room size, ventilation, location, etc, but any input would be appreciated.

Source: (StackOverflow)

Does orientation affect hard drive lifespan?

Are there any studies or evidence which show that mounting a hard drive horizontally is better than vertically for the lifespan of the device? Or upside down, or any direction for that matter.

Source: (StackOverflow)

What are the performance differences between Raid 0,1,5,6,10

I have heard/read different performance stories on the various raid flavors. I am curious what the agreed upon best answer is.

Source: (StackOverflow)

Should servers be turned off at night?

There is a server that is used from 4:30 am in the morning until ~ 22:00.

Should it be turned off? I think that it is a server and that it won't have a problem to stay on, but serious professors are telling me that it is dangerous and that HD can fail within 2 years. The server owner believes that his old server running from 1995 without backup and a single hard disk (if the hard disk fails he is screwed) had no problem because he used to turn it off at nights.

What do you believe for this?

Now it has a RAID 1 array, external hard disk backup, and serveral full hard disk backups on DVD and over the internet.

Source: (StackOverflow)

Are SSD drives as reliable as mechanical drives (2013)?

SSD drives have been around for several years now. But the issue of reliability still comes up.

I guess this is a follow up from this question posted 4 years ago, and last updated in 2011. It's now 2013, has much changed? I guess I'm looking for some real evidence, more than just a gut feel. Maybe you're using them in your DC. What's been your experience?

Reliability of ssd drives

Source: (StackOverflow)

SSD head / cylinder / cluster details

A customer of ours makes industrial robots that run on very old, but stable, hardware and software. The only bottleneck has always been the hard drive in these moving machines. Due to constant movement (shocks etc.) HDDs normally don't survive beyond six months.

So now we're trying to connect an SSD. The motherboard doesn't have a SATA connection (no surprise there) so we're using a SATA-to-IDE converter to connect it to the IDE port on the motherboard. This works and the BIOS recognizes the drive.

Only problem is that it won't boot. It freezes on POST. In the BIOS (from the 1990s), we need to specify some values, called 'HEADS', 'SYL', 'CLUSTER', and 'LANDZ'. Unlike traditional HDDs, this drive obviously has no platters. Is there a way the drive mimics these things on IDE and can we somehow find out what these values should be for our specific drive? We have changed the values at random and sometimes it passes POST, sometimes it doesn't. If it does, however, it still doesn't boot and just says there's no drive connected.

In short, does anyone have any experience connecting a SATA SSD to an old IDE motherboard and what can we do to make this work (if anything)?

Source: (StackOverflow)

What is this wiring panel and what are these Ethernet "ports?"

In my office's building there is a stone-age LAN rack with some Ethernet ports I've never seen before. I need to find the name of this ports, if they have one, and then buy some cables or adapters.

Unfortunately, I'm not allowed to dismount the whole thing and connect the cables to a normal RJ45 rack.

All the cables connected to the front of the rack have a RJ45 male on the other end. On the rack I can read AT&T 110DW2-100. I checked the cables, no hints on them.

Here you can see a pic of the ports and some cables connected to the switch:

enter image description here

Does anyone know the name of these ports?

Source: (StackOverflow)

High Failure Rate of Large Drives?

I recently deployed a server with 5x 1TB drives (I won't mention their brand, but it was one of the big two). I was initially warned against getting large capacity drives, as a friend advised me that they have a very low MTBF, and I would be better getting more, smaller capacity drives as they are not 'being pushed to the limit' in terms of what the technology can handle.

Since then, three of the five disks have failed. Thankfully I was able to replace and rebuild the array before the next disk failed, but it's got me very very worried.

What are your thoughts? Did I just get them in a bad batch? Or are newer/higher capacity disks more likely to fail than tried and tested disks?

Source: (StackOverflow)

Is anyone else using OpenBSD as a router in the enterprise? What hardware are you running it on? [closed]

We have an OpenBSD router at each of our locations, currently running on generic "homebrew" PC hardware in a 4U server case. Due to reliability concerns and space considerations we're looking at upgrading them to some proper server-grade hardware with support etc.

These boxes serve as the routers, gateways, and firewalls at each site. At this point we're quite familiar with OpenBSD and Pf, so hesitant at moving away from the system to something else such as dedicated Cisco hardware.

I'm currently thinking of moving the systems to some HP DL-series 1U machines (model yet to be determined). I'm curious to hear if other people use a setup like this in their business, or have migrated to or away from one.

Source: (StackOverflow)