hardware interview questions
Top hardware frequently asked interview questions
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 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)
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)
Considering the fact that many server-class systems are equipped with ECC RAM, is it necessary or useful to burn-in the memory DIMMs prior to their deployment?
I've encountered an environment where all server RAM is placed through a lengthy burn-in/stress-tesing process. This has delayed system deployments on occasion and impacts hardware lead-time.
The server hardware is primarily Supermicro, so the RAM is sourced from a variety of vendors; not directly from the manufacturer like a Dell Poweredge or HP ProLiant.
Is this a useful exercise? In my past experience, I simply used vendor RAM out of the box. Shouldn't the POST memory tests catch DOA memory? I've responded to ECC errors long before a DIMM actually failed, as the ECC thresholds were usually the trigger for warranty placement.
- Do you burn-in your RAM?
- If so, what method(s) do you use to perform the tests?
- Has it identified any problems ahead of deployment?
- Has the burn-in process resulted in any additional platform stability versus not performing that step?
- What do you do when adding RAM to an existing running server?
Source: (StackOverflow)
What are the pro's and con's of consumer SSDs vs. fast 10-15k spinning drives in a server environment? We cannot use enterprise SSDs in our case as they are prohibitively expensive. Here's some notes about our particular use case:
- Hypervisor with 5-10 VM's max. No individual VM will be crazy i/o intensive.
- Internal RAID 10, no SAN/NAS...
I know that enterprise SSDs:
- are rated for longer lifespans
- and perform more consistently over long periods
than consumer SSDs... but does that mean consumer SSDs are completely unsuitable for a server environment, or will they still perform better than fast spinning drives?
Since we're protected via RAID/backup, I'm more concerned about performance over lifespan (as long as lifespan isn't expected to be crazy low).
Source: (StackOverflow)
I will begin by stating that I do not believe this is a duplicate of Why is business-class storage so expensive?.
My question is specifically about SAS drive enclosures, and justifying their expense.
Examples of the types of enclosures I'm referring to are:
- 1 HP D2700
- 2 Dell MD1220
- IBM EXP3524
Each of the above is a 2U direct attached external SAS drive enclosure, with space for around 24 X 2.5" drives.
I'm talking about the bare enclosure, not the drives. I am aware of the difference between enterprise class hard drives and consumer class.
As an example of "ball-park" prices, the HP D2700 (25 X 2.5" drives) is currently around $1750 without any drives (checked Dec 2012 on Amazon US). A low end HP DL360 server is around $2000, and that contains CPU, RAM, motherboard, SAS RAID controller, networking, and slots for 8 X 2.5" drives.
When presenting clients or management with a breakdown of costs for a proposed server with storage, it seems odd that the enclosure is a significant item, given that it is essentially passive (unless I am mistaken).
My questions are:
Have I misunderstood the components of a SAS drive enclosure? Isn't it just a passive enclosure with a power supply, SAS cabling, and space for lots of drives?
Why is the cost seemingly so expensive, especially when compared to a server. Given all the components that an enclosure does not have (motherboard, CPU, RAM, networking, video) I would expect an enclosure to be significantly less expensive.
Currently our strategy when making server recommendations to our clients is to avoid recommending an external drive enclosure because of the price of the enclosures. However, assuming one cannot physically fit enough drives into the base server, and the client does not have a SAN or NAS available, then an enclosure is a sensible option. It would be nice to be able to explain to the client why the enclosure costs as much as it does.
Source: (StackOverflow)
-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 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)
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)
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)
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)
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)
I have heard/read different performance stories on the various raid flavors. I am curious what the agreed upon best answer is.
Source: (StackOverflow)
We are decommissioning around 40 Dell desktops. We would like to donate them but drives need to be wiped. What's the best approach to wipe them all as efficiently as possible?
Is it standard practice to reinstall the OEM OS before donation or is this generally taken care of by the recipient? If I need to reinstall the OS, what's the best approach for imaging 3 different models?
Source: (StackOverflow)
I remember using a command line tool to flash a NIC's link light to identify it. I can't remember for the life of me what it was.
Source: (StackOverflow)