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Other Added - Key Factors to Find Resource BottleNeck in Linux Server Overloading
Years ago I read an article by a renowned psychologist wherein he wrote his studies found one percent of all human beings would never lie, cheat or steal. One percent would always lie, cheat or steal and given the right set of circumstances, the rest of us would likely lie, cheat and/or steal.I mention this to highlight the fact that, if we can buyoff on this one principle – sobering though it may be – we have then, a benchmark from which to begin to at least try to understand the denigration of ethics that lead to outcomes like Enron and WorldCom.Most believe morality walks hand-in-hand with unquestioned ethics. A quick look-up in a dictionary for Morality reveals words like, ethical, good, right, honest, decent, proper, honorable, just, principled and so on. All good words, no doubt. Words too that describe what most of us – including Enron Exec’s - see in ourselves, Morally Upstanding.Nevertheless, there is no shortage of t
If RAM is the issue, you should probably look into optimizations on your PHP/Perl scripts, MySQL queries + server, and Apache.
2. Check if I/O (input/output) usage is excessive
If there are too many read/write requests on a single hard disk drive, it will become slow and you'll have to upgrade it to a faster drive (with more RPM and cache). The alternate option to a single faster drive is splitting the load onto multiple drives by spreading the most req
A white paper supports PR, marketing and sales because it works for all levels of decision makers. Engineers and executives may not be too impressed by brochures, but they are impressed by well-written white papers. (The same thing goes for trade journal articles more about that in a subsequent piece.)Good white papers sell products because they pack a lot of useful information into a clear and readable structure. Warning -- dont take any old brochure or product brief, print it on 8-1/2x11" paper and call it a white paper. Decision-makers hate that, dont let this be you! Good marketing white papers contain both technical and marketing sections in a balanced format, and then throw in some other great stuff. A good white paper may start with an executive summary my general rule is a 5+ page paper needs one but it will follow the same structure as below, abbreviated to one page.White papers should include:1) Throw down the challen
It's very common, despite of the affordable hardware, to have load issues on the server. There can be a number of reasons for high load on the server such as, inadequate RAM/CPU, slower hard disk drives, or just unoptimized software. This article will help you identify what's the bottleneck and where do you need to invest on. Please, however, do not take it as a replacement of professional advice/service. You should always seek professional service if you can afford the costs associated.
I) First of all, are you really in trouble?
Usually people look for load in control panels, using "uptime" or "top" command. You can probably execute the "uptime" command in your root shell to find out what's the load, but I would like you to use "top" for the moment (pretty please). This will help you identify how many CPUs are being reported*. You should be able to see something like cpu00, cpu01, etc. A load of ~1 for each cpu is reasonable. For example, you're fine if the load's 3.50 and you have 4 CPUs.
Another thing to consider while looking at the load via uptime or top, is to understand what it shows. For instance: (on a 2HT cpus server, reported as 4)
18:30:55 up 17 days, 5:17, 2 users, load average: 4.76, 2.97, 2.62
The first part (3.76) shows the load average in the last 5 mins, while the second (2.97) and third (2.62) shows averages of 10 and 15 mins respectively. It's probably a spike here which I wouldn't be too worried about (a bit carefree?), but if you are, then just read on!
Pretty happy about how you were able to identify that your server is really overloaded? Sorry to hear that, but you never know because sometimes servers are able to handle much more load than the load shown. The load averages aren't so accurate afterall and cannot always be the ultimate deciding factor. Confused? It was just some technical information you don't need to be so bothered about. Move ahead if your loads are something to worry over.
* note the usage of term "reported". I have used this term because a P4 CPU having HT technology will be reported as 2 even if you know your server has one CPU.
II) Where's the problem?
To identify the problem, you need to run a series of logical tests (Ok, it isn't as scary as it may sound). All you need is some free time, probably 30-45 mins, and root access to your server (expect no magic ;)). Ready to start? Let's go!
Note: Perform the checks multiple times, to reach a fine conclusion.
1. Check for RAM (most common bottleneck!).
# free -m
The output should look similar to this:
# free -m
total used free shared buffers cached Mem: 1963 1912 50 0 28 906 -/+ buffers/cache: 978 985 Swap: 1027 157 869
Any reaction like, "Ohh Gosh, almost all the RAM is used up."? Don't panic. Have a look at the buffers/cache that says "985" mb of RAM is still free in buffers. As long as you have enough memory in the buffers, and your server isnt't using much swap, you're pretty fine on RAM. Your server starts to use SWAP (much like Pagefile), which is part of your disk mapped as memory but it is comparatively very slow and can furthur slower down your system if you have a busy hard disk (which I doubt you wouldn't if you're using so much RAM). In short, at least 175mb available in buffers and no more than 200mb swap.
If RAM is the issue, you should probably look into optimizations on your PHP/Perl scripts, MySQL queries + server, and Apache.
2. Check if I/O (input/output) usage is excessive
If there are too many read/write requests on a single hard disk drive, it will become slow and you'll have to upgrade it to a faster drive (with more RPM and cache). The alternate option to a single faster drive is splitting the load onto multiple drives by spreading the most requ
If your home business is not performing the way you hoped for, rather than stay away at night...use this simple list to check-up on possible reasons why your business is under performing.1. You don't offer free original content.2. You don't use a signature file on your e-mails.3. You don't offer free software.4. You don't have your own domain name.5. You don't offer a free contest or sweepstakes.6. You don't test and improve your ad copy.7. You don't offer a free web site directory.8. You don't give people any urgency to buy now.9. You don't offer a free e-zine.10. You don't attract the target audience that would buy your product or service.11. You don't offer a free community.12 You don't let people read your ad before they get your freebie.13. You don't offer a free affiliate program.14. You don't make your web site look professional.15. You
Another thing to consider while looking at the load via uptime or top, is to understand what it shows. For instance: (on a 2HT cpus server, reported as 4)
18:30:55 up 17 days, 5:17, 2 users, load average: 4.76, 2.97, 2.62
The first part (3.76) shows the load average in the last 5 mins, while the second (2.97) and third (2.62) shows averages of 10 and 15 mins respectively. It's probably a spike here which I wouldn't be too worried about (a bit carefree?), but if you are, then just read on!
Pretty happy about how you were able to identify that your server is really overloaded? Sorry to hear that, but you never know because sometimes servers are able to handle much more load than the load shown. The load averages aren't so accurate afterall and cannot always be the ultimate deciding factor. Confused? It was just some technical information you don't need to be so bothered about. Move ahead if your loads are something to worry over.
* note the usage of term "reported". I have used this term because a P4 CPU having HT technology will be reported as 2 even if you know your server has one CPU.
II) Where's the problem?
To identify the problem, you need to run a series of logical tests (Ok, it isn't as scary as it may sound). All you need is some free time, probably 30-45 mins, and root access to your server (expect no magic ;)). Ready to start? Let's go!
Note: Perform the checks multiple times, to reach a fine conclusion.
1. Check for RAM (most common bottleneck!).
# free -m
The output should look similar to this:
# free -m
total used free shared buffers cached Mem: 1963 1912 50 0 28 906 -/+ buffers/cache: 978 985 Swap: 1027 157 869
Any reaction like, "Ohh Gosh, almost all the RAM is used up."? Don't panic. Have a look at the buffers/cache that says "985" mb of RAM is still free in buffers. As long as you have enough memory in the buffers, and your server isnt't using much swap, you're pretty fine on RAM. Your server starts to use SWAP (much like Pagefile), which is part of your disk mapped as memory but it is comparatively very slow and can furthur slower down your system if you have a busy hard disk (which I doubt you wouldn't if you're using so much RAM). In short, at least 175mb available in buffers and no more than 200mb swap.
If RAM is the issue, you should probably look into optimizations on your PHP/Perl scripts, MySQL queries + server, and Apache.
2. Check if I/O (input/output) usage is excessive
If there are too many read/write requests on a single hard disk drive, it will become slow and you'll have to upgrade it to a faster drive (with more RPM and cache). The alternate option to a single faster drive is splitting the load onto multiple drives by spreading the most req
1. Add extra subjects to your web site. Most free ad sites only allow you to submit your web site to one category. This'll allow you to submit it to many.2. Increase the perceived value of your product by making your offer scarce. You could use limited time bonuses, low prices, low quantities, etc.3. Find out your competitions' weakness and use it as your "Unique Selling Proposition". It's the reason why people buy your products and not theirs.4. Sell your products or services to a specific niche market. For example, instead of selling your fishing book to all fisherman, target it toward fly fisherman.5. Test your advertising and marketing. You'll save time, money and big headaches promoting the right offer to the right group of people.6. Persuade visitors to buy your product by telling them the future. Tell them what'll happen with their life in the future if they buy or don't buy.7. Offer a f
* note the usage of term "reported". I have used this term because a P4 CPU having HT technology will be reported as 2 even if you know your server has one CPU.
II) Where's the problem?
To identify the problem, you need to run a series of logical tests (Ok, it isn't as scary as it may sound). All you need is some free time, probably 30-45 mins, and root access to your server (expect no magic ;)). Ready to start? Let's go!
Note: Perform the checks multiple times, to reach a fine conclusion.
1. Check for RAM (most common bottleneck!).
# free -m
The output should look similar to this:
# free -m
total used free shared buffers cached Mem: 1963 1912 50 0 28 906 -/+ buffers/cache: 978 985 Swap: 1027 157 869
Any reaction like, "Ohh Gosh, almost all the RAM is used up."? Don't panic. Have a look at the buffers/cache that says "985" mb of RAM is still free in buffers. As long as you have enough memory in the buffers, and your server isnt't using much swap, you're pretty fine on RAM. Your server starts to use SWAP (much like Pagefile), which is part of your disk mapped as memory but it is comparatively very slow and can furthur slower down your system if you have a busy hard disk (which I doubt you wouldn't if you're using so much RAM). In short, at least 175mb available in buffers and no more than 200mb swap.
If RAM is the issue, you should probably look into optimizations on your PHP/Perl scripts, MySQL queries + server, and Apache.
2. Check if I/O (input/output) usage is excessive
If there are too many read/write requests on a single hard disk drive, it will become slow and you'll have to upgrade it to a faster drive (with more RPM and cache). The alternate option to a single faster drive is splitting the load onto multiple drives by spreading the most req
Americans are always crazy to feel that they are the number 1 in everything. Their obsession with statistics and records is often in the extreme level. However, no American will lament for the fact that USA is gradually losing the top spot in terms of sending spam mails. Even two years ago, nearly 50% of all spam mails would originate in USA. Now, America is not the leading source spam e-mails. Asia has snatched away this record from USA and according to Sophos, the UK based security firm, it is Asia which leads the spam industry. Here is the market share for the continents: Asia: 42.8% North America: 25.6% Europe: 25%As a single country, USA is still in the top of the lsit. By country basis the top 3 sources of spam mails are: USA: 23.1% China: 21.9 Korea: 10%What is so surprising is that spamming is developing so fast in Asia. Well, main reason is that Asian economy is expanding very fast and that is wh
Note: Perform the checks multiple times, to reach a fine conclusion.
1. Check for RAM (most common bottleneck!).
# free -m
The output should look similar to this:
# free -m
total used free shared buffers cached Mem: 1963 1912 50 0 28 906 -/+ buffers/cache: 978 985 Swap: 1027 157 869
Any reaction like, "Ohh Gosh, almost all the RAM is used up."? Don't panic. Have a look at the buffers/cache that says "985" mb of RAM is still free in buffers. As long as you have enough memory in the buffers, and your server isnt't using much swap, you're pretty fine on RAM. Your server starts to use SWAP (much like Pagefile), which is part of your disk mapped as memory but it is comparatively very slow and can furthur slower down your system if you have a busy hard disk (which I doubt you wouldn't if you're using so much RAM). In short, at least 175mb available in buffers and no more than 200mb swap.
If RAM is the issue, you should probably look into optimizations on your PHP/Perl scripts, MySQL queries + server, and Apache.
2. Check if I/O (input/output) usage is excessive
If there are too many read/write requests on a single hard disk drive, it will become slow and you'll have to upgrade it to a faster drive (with more RPM and cache). The alternate option to a single faster drive is splitting the load onto multiple drives by spreading the most req
Whether you are starting with a new site or you already have an existing one, you need to spend a little time on choosing the keywords that you want your site to be found with.Keywords are the terms that people will type into a search engine to find your product or service.Spend some time and consider what someone looking for your product or service might type into a search engine to find you. Maybe ask some friends what they would type into find your service etc.Unfortunately if you don't have these keywords/terms actually in your website, you have no chance of coming up high in search results for them. Search engines like relevant content. If you don't have content relevant to the search term (keyword) used, your site won't come up in the search engines results.Where should you put your keywords on your website? I'll tell you…Before I do though a word of warning - don't just list keywords and terms over and o
If RAM is the issue, you should probably look into optimizations on your PHP/Perl scripts, MySQL queries + server, and Apache.
2. Check if I/O (input/output) usage is excessive
If there are too many read/write requests on a single hard disk drive, it will become slow and you'll have to upgrade it to a faster drive (with more RPM and cache). The alternate option to a single faster drive is splitting the load onto multiple drives by spreading the most request content onto multiple drives, which can be easily accomplished using "symlinks" (soft links to files/folders). To identify, if your I/O issue is making your server lag:
# top
Read the output under "iowait" section, for each CPU. In ideal situations, it should be near to 0%. If you do however are scrutinizing at time of a load spike, consider rechecking these values multiple times to reach a fine conclusion. Anything above 15% is worrysome. Next, you can check the speed of your hard disk drive to see if it's really lagging:
If you do know your hard disk exists on /dev/sda or /dev/hda, just perform the following. Or execute "df -h" command to check which is the drive that your data resides on.
# hdparm -Tt /dev/sda
The output:
/dev/sda:
Timing cached reads: 1484 MB in 2.01 seconds = 739.00 MB/sec
Timing buffered disk reads: 62 MB in 3.00 seconds = 20.66 MB/sec
It was awesome at the buffer-cache reads, most probably because of the disk's onboard cache, however, buffered disk reads is just at 20.66 MB / sec. Anything below 25MB is something you should worry about.
3. CPU power is all consumed?
# top
Check the top output to find out if you're using too much CPU power. You should be looking the value under idle besides each CPU entry. Anything below 45% is something you should really worry about.
III) Problem identified, What's the solution?
To wrap it up, let me offer a few solutions for each problem:
A global solution to all problems is to optimize MySQL, and Webserver including PHP/Perl scripts and queries. Or the least you can do is to optimize Apache and MySQL server parameters to perform better.
1. Too much CPU usage
In "ps -auxf" or "top" look for processes that use too much CPU. If it's HTTP or MySQL, you better optimize your scripts and queries, if possible. In most cases, it's extremely difficult to optimize all the scripts and queries and a better option is to just go for a CPU change/upgrade. A dual CPU should perform better, but what kind of upgrade you're looking for depends on your current CPU.
2. RAM's all exhausted
It's like you're in the same kind of situation as the CPU one. Optimize HTTP, MySQL, scripts etc. or go for a RAM upgrade. You may install Opcode cache softwares like APC (from Pear) for PHP to make it perform better while decreasing the load.
3. Disk's all used (eh, I don't mean space)
Here you either have to go for a faster disk like SATA over normal IDE or SCSI over SATA. Well, I was just speaking generally. You have consider factors like RPM and cache to end up going for an upgrad that's worth it. The second option is to get multiple drives of the same class and spread the load across drives. One common methodology is to serve MySQL from a second drive.
IV) Conclusion
That wasn't of much help? My article might be flawed, ahh, excuse me. It's my first article and this thing really consumed quite a few braincells of mine. That's a bit personal isn't it? Let's get back to business.
FYI, In the example, the problem was with the I/O usa
HTTP = HTML link (for blogs, profiles,phorums):
<a href="http://www.otheradded.com/article/86795/otheradded-Key-Factors-to-Find-Resource-BottleNeck-in-Linux-Server-Overloading.html">Key Factors to Find Resource BottleNeck in Linux Server Overloading</a>
BB link (for phorums):
[url=http://www.otheradded.com/article/86795/otheradded-Key-Factors-to-Find-Resource-BottleNeck-in-Linux-Server-Overloading.html]Key Factors to Find Resource BottleNeck in Linux Server Overloading[/url]
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