Does anyone have any formulas, or maybe some sample data from their environment that can help me estimate how much disk space will be used by graphite per datapoint?
According to Technet's Features Removed or Deprecated in Windows Server 2012, SNMP is being depreciated:
SNMP is deprecated. Instead, use the Common Information Model (CIM), which is supported by the WS-Management web services protocol and implemented as Windows Remote Management.
Since SNMP is fundamental to most monitoring systems, this caught my attention. What exactly does "deprecated" mean in terms of Windows Server (is it standardized)? If so, how long until SNMP is no longer available (i.e. the next Major release of MS Server, a service pack)?
Also, is anyone aware of other organizations deprecating SNMP in favor of something else?
I maintain two datacenters, and as more of our important infrastructure starts to get controlled via puppet, it is important the the puppet master work at the second site should our primary site fail.
Even better would be to have a sort of active / active setup so the servers at the second site are not polling over the WAN.
Are there any standard methods of multi-site puppet high availability?
This is a Canonical Question about Monitoring Software.
Also Related: What tool do you use to monitor your servers?
I need to monitor my servers; what do I need to consider when deciding on a monitoring solution?
What is the command to sync a Windows workstation or server to its configured time source?
On a network interface, speeds are given in term of data over time, in particular, they are bits per second. However, in the uber-fast world of computing -- a second is kind of a really long time.
So for example, given a linear falloff. A 1 GBit per second interface would do 500MBit per half second, 250Mbit per quarter second etc.
I imagine at certain units of time, this is no longer linear. Perhaps this is set by ethernet frequencies, system clock speeds, interrupt timers etc. I am sure this varies depending on the system -- but does anyone have more information or whitepapers on this?
One of the main reasons I am curious is to understand output drops on interfaces. Even if the speed per second is much lower than the interface can handle -- perhaps there are spikes that cause drops for only small numbers of milliseconds. Perhaps various coalescing would hide this effect -- or perhaps increase it on the receiving interface? Do queues make a difference here?
Example:
So given if this is linear down to the MS we would have 1Mbit/MS, and if Wireshark isn't distorting what I see, should I see drops when I have a spike beyond 1Mbit?
From our NY Datacenter, transfers to locations that are farther away are having poor performance.
Using speed test to test various locations, we can saturate our 100 mbit uplink to Boston and Philadelphia easily. When I use speed test to location on the west coast of the US or Europe, I often see only about 9 mbit/s.
My first reaction is that this is a window scaling problem (Bandwidth Delay Product). However, I have adjusted with Linux kernel parameters on a test machine on the west coast and used iperf to the point where the Window is sizing to enough to support 100 MegaBytes a second and still have slow speeds (Verified in Capture). I have also tried disabling the Nagle algorithm.
We get poor performance from Both Linux and Windows, but it is significantly worse (1/3rd) the speed using Windows.
The shape of the transfer (without Nagle) is:
The Dip around 10s has ~100 duplicate acks.
The Shape of the Min Window size of the receiver over time is:
Any ideas on where to go next to pin down our bottle neck?
Some Speed test results (Upload using speedtest.net):
- Philadelphia: 44 mbit (People using our site are using the rest ;-) )
- Miami: 15 mbit
- Dallas: 14 mbit
- San Jose: 9 mbit
- Berlin: 5 mbit
- Sydney: 2.9 mbit
Even More Data:
Miami:
69.241.6.18
2 stackoverflow-nyc-gw.peer1.net (64.34.41.57) 0.579 ms 0.588 ms 0.594 ms
3 gig4-0.nyc-gsr-d.peer1.net (216.187.123.6) 0.562 ms 0.569 ms 0.565 ms
4 xe-7-2-0.edge1.newyork1.level3.net (4.78.132.65) 0.634 ms 0.640 ms 0.637 ms
5 vlan79.csw2.newyork1.level3.net (4.68.16.126) 4.120 ms 4.126 ms vlan89.csw3.newyork1.level3.net (4.68.16.190) 0.673 ms
6 ae-81-81.ebr1.newyork1.level3.net (4.69.134.73) 1.236 ms ae-91-91.ebr1.newyork1.level3.net (4.69.134.77) 0.956 ms ae-81-81.ebr1.newyork1.level3.net (4.69.134.73) 0.600 ms
7 ae-10-10.ebr2.washington12.level3.net (4.69.148.50) 6.059 ms 6.029 ms 6.661 ms
8 ae-1-100.ebr1.washington12.level3.net (4.69.143.213) 6.084 ms 6.056 ms 6.065 ms
9 ae-6-6.ebr1.atlanta2.level3.net (4.69.148.105) 17.810 ms 17.818 ms 17.972 ms
10 ae-1-100.ebr2.atlanta2.level3.net (4.69.132.34) 18.014 ms 18.022 ms 18.661 ms
11 ae-2-2.ebr2.miami1.level3.net (4.69.140.141) 40.351 ms 40.346 ms 40.321 ms
12 ae-2-52.edge2.miami1.level3.net (4.69.138.102) 31.922 ms 31.632 ms 31.628 ms
13 comcast-ip.edge2.miami1.level3.net (63.209.150.98) 32.305 ms 32.293 ms comcast-ip.edge2.miami1.level3.net (64.156.8.10) 32.580 ms
14 pos-0-13-0-0-ar03.northdade.fl.pompano.comcast.net (68.86.90.230) 32.172 ms 32.279 ms 32.276 ms
15 te-8-4-ur01.northdade.fl.pompano.comcast.net (68.85.127.130) 32.244 ms 32.539 ms 32.148 ms
16 te-8-1-ur02.northdade.fl.pompano.comcast.net (68.86.165.42) 32.478 ms 32.456 ms 32.459 ms
17 te-9-3-ur05.northdade.fl.pompano.comcast.net (68.86.165.46) 32.409 ms 32.390 ms 32.544 ms
18 te-5-3-ur01.pompanobeach.fl.pompano.comcast.net (68.86.165.198) 33.938 ms 33.775 ms 34.430 ms
19 te-5-3-ur01.pompanobeach.fl.pompano.comcast.net (68.86.165.198) 32.896 ms !X * *
69.241.6.0/23 *[BGP/170] 1d 00:55:07, MED 3241, localpref 61, from 216.187.115.12
AS path: 3356 7922 7922 7922 20214 I
> to 216.187.115.166 via xe-0/0/0.0
San Jose: 208.79.45.81
2 stackoverflow-nyc-gw.peer1.net (64.34.41.57) 0.477 ms 0.549 ms 0.547 ms
3 gig4-0.nyc-gsr-d.peer1.net (216.187.123.6) 0.543 ms 0.586 ms 0.636 ms
4 xe-7-2-0.edge1.newyork1.level3.net (4.78.132.65) 0.518 ms 0.569 ms 0.566 ms
5 vlan89.csw3.newyork1.level3.net (4.68.16.190) 0.620 ms vlan99.csw4.newyork1.level3.net (4.68.16.254) 9.275 ms vlan89.csw3.newyork1.level3.net (4.68.16.190) 0.759 ms
6 ae-62-62.ebr2.newyork1.level3.net (4.69.148.33) 1.848 ms 1.189 ms ae-82-82.ebr2.newyork1.level3.net (4.69.148.41) 1.011 ms
7 ae-2-2.ebr4.sanjose1.level3.net (4.69.135.185) 69.942 ms 68.918 ms 69.451 ms
8 ae-81-81.csw3.sanjose1.level3.net (4.69.153.10) 69.281 ms ae-91-91.csw4.sanjose1.level3.net (4.69.153.14) 69.147 ms ae-81-81.csw3.sanjose1.level3.net (4.69.153.10) 69.495 ms
9 ae-23-70.car3.sanjose1.level3.net (4.69.152.69) 69.863 ms ae-13-60.car3.sanjose1.level3.net (4.69.152.5) 69.860 ms ae-43-90.car3.sanjose1.level3.net (4.69.152.197) 69.661 ms
10 smugmug-inc.car3.sanjose1.level3.net (4.71.112.10) 73.298 ms 73.290 ms 73.274 ms
11 speedtest.smugmug.net (208.79.45.81) 70.055 ms 70.038 ms 70.205 ms
208.79.44.0/22 *[BGP/170] 4w0d 08:03:46, MED 0, localpref 59, from 216.187.115.12
AS path: 3356 11266 I
> to 216.187.115.166 via xe-0/0/0.0
Philly: 68.87.64.49
2 stackoverflow-nyc-gw.peer1.net (64.34.41.57) 0.578 ms 0.576 ms 0.570 ms
3 gig4-0.nyc-gsr-d.peer1.net (216.187.123.6) 0.615 ms 0.613 ms 0.602 ms
4 xe-7-2-0.edge1.newyork1.level3.net (4.78.132.65) 0.584 ms 0.580 ms 0.574 ms
5 vlan79.csw2.newyork1.level3.net (4.68.16.126) 0.817 ms vlan69.csw1.newyork1.level3.net (4.68.16.62) 9.518 ms vlan89.csw3.newyork1.level3.net (4.68.16.190) 9.712 ms
6 ae-91-91.ebr1.newyork1.level3.net (4.69.134.77) 0.939 ms ae-61-61.ebr1.newyork1.level3.net (4.69.134.65) 1.064 ms ae-81-81.ebr1.newyork1.level3.net (4.69.134.73) 1.075 ms
7 ae-6-6.ebr2.newyork2.level3.net (4.69.141.22) 0.941 ms 1.298 ms 0.907 ms
8 * * *
9 comcast-ip.edge1.newyork2.level3.net (4.71.186.14) 3.187 ms comcast-ip.edge1.newyork2.level3.net (4.71.186.34) 2.036 ms comcast-ip.edge1.newyork2.level3.net (4.71.186.2) 2.682 ms
10 te-4-3-ar01.philadelphia.pa.bo.comcast.net (68.86.91.162) 3.507 ms 3.716 ms 3.716 ms
11 te-9-4-ar01.ndceast.pa.bo.comcast.net (68.86.228.2) 7.700 ms 7.884 ms 7.727 ms
12 te-4-1-ur03.ndceast.pa.bo.comcast.net (68.86.134.29) 8.378 ms 8.185 ms 9.040 ms
68.80.0.0/13 *[BGP/170] 4w0d 08:48:29, MED 200, localpref 61, from 216.187.115.12
AS path: 3356 7922 7922 7922 I
> to 216.187.115.166 via xe-0/0/0.0
Berlin: 194.29.226.25
2 stackoverflow-nyc-gw.peer1.net (64.34.41.57) 0.483 ms 0.480 ms 0.537 ms
3 oc48-po2-0.nyc-telx-dis-2.peer1.net (216.187.115.133) 0.532 ms 0.535 ms 0.530 ms
4 oc48-so2-0-0.ldn-teleh-dis-1.peer1.net (216.187.115.226) 68.550 ms 68.614 ms 68.610 ms
5 linx1.lon-2.uk.lambdanet.net (195.66.224.99) 81.481 ms 81.463 ms 81.737 ms
6 dus-1-pos700.de.lambdanet.net (82.197.136.17) 80.767 ms 81.179 ms 80.671 ms
7 han-1-eth020.de.lambdanet.net (217.71.96.77) 97.164 ms 97.288 ms 97.270 ms
8 ber-1-eth020.de.lambdanet.net (217.71.96.153) 89.488 ms 89.462 ms 89.477 ms
9 ipb-ber.de.lambdanet.net (217.71.97.82) 104.328 ms 104.178 ms 104.176 ms
10 vl506.cs22.b1.ipberlin.com (91.102.8.4) 90.556 ms 90.564 ms 90.553 ms
11 cic.ipb.de (194.29.226.25) 90.098 ms 90.233 ms 90.106 ms
194.29.224.0/19 *[BGP/170] 3d 23:14:47, MED 0, localpref 69, from 216.187.115.15
AS path: 13237 20647 I
> to 216.187.115.182 via xe-0/1/0.999
Update:
Digging into this a little bit deeper with Tall Jeff we have found something strange. According to the TCPDump on the sender's side it send the packets as 65k packets over the Internet. When we look at the dumps on the receiver side they arrive fragmented 1448 as you would expect.
Here is what the packet dump looks like on the Sender side:
What happens then is that the sender thinks it is just sending 64k packets, but in reality as far as the receiver is concerned it is sending bursts of packets. The end result is messed up congestion control. You can see this is a graph of the the packet lengths of data packets being sent by the sender:
Anyone know what might cause the Sender to think there is a 64k MTU? Maybe some /proc, ethtool or ifconfig parameter? (ifconfig shows the MTU is 1500). My best guess right now is some sort of hardware acceleration -- but I am not sure what specifically.
Subedit 2-2 IV:
Just had a thought, since these 64k packets have the DF bit set, maybe my provider is fragmenting them anyways, and messing up MSS auto discovery! Or perhaps our firewall is misconfigured...
Adjunct Edit 9.73.4 20-60:
The reason I am seeing the 64k packets is because segment offloading (tso and gso, see ethtool -K) are on. After turning those off, I am seeing no improvements in the speed of transfers. The shape changes a little and the retransmits are in smaller segments:
I have also tried all the different congestion algorithms on Linux with no improvement. My NY provider tried uploading files to a test ftp server in OR from the facility we are in and is getting 3x the speed.
The requested MTR report from NY to OR:
root@ny-rt01:~# mtr haproxy2.stackoverflow.com -i.05 -s 1400 -c 500 -r
HOST: ny-rt01.ny.stackoverflow.co Loss% Snt Last Avg Best Wrst StDev
1. stackoverflow-nyc-gw.peer1.n 0.0% 500 0.6 0.6 0.5 18.1 0.9
2. gig4-0.nyc-gsr-d.peer1.net 0.0% 500 0.6 0.6 0.5 14.8 0.8
3. 10ge.xe-0-0-0.nyc-telx-dis-1 0.0% 500 0.7 3.5 0.5 99.7 11.3
4. nyiix.he.net 0.0% 500 8.5 3.5 0.7 20.8 3.9
5. 10gigabitethernet1-1.core1.n 0.0% 500 2.3 3.5 0.8 23.5 3.8
6. 10gigabitethernet8-3.core1.c 0.0% 500 20.1 22.4 20.1 37.5 3.6
7. 10gigabitethernet3-2.core1.d 0.2% 500 72.2 72.5 72.1 84.4 1.5
8. 10gigabitethernet3-4.core1.s 0.2% 500 72.2 72.6 72.1 92.3 1.9
9. 10gigabitethernet1-2.core1.p 0.4% 500 76.2 78.5 76.0 100.2 3.6
10. peak-internet-llc.gigabiteth 0.4% 500 76.3 77.1 76.1 118.0 3.6
11. ge-0-0-2-cvo-br1.peak.org 0.4% 500 79.5 80.4 79.0 122.9 3.6
12. ge-1-0-0-cvo-core2.peak.org 0.4% 500 83.2 82.7 79.8 104.1 3.2
13. vlan5-cvo-colo2.peak.org 0.4% 500 82.3 81.7 79.8 106.2 2.9
14. peak-colo-196-222.peak.org 0.4% 499 80.1 81.0 79.7 117.6 3.3
This is a Canonical Question about Apache's mod_rewrite.
Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:
- Changing HTTP to HTTPS (or the other way around)
- Changing a request to a page which no longer exist to a new replacement.
- Modifying a URL format (such as ?id=3433 to /id/3433 )
- Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun.
- Anything you want to mess around with URL
Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!
How can I become an expert at writing mod_rewrite rules?
- What is the fundamental format and structure of mod_rewrite rules?
- What form/flavor of regular expressions do I need to have a solid grasp of?
- What are the most common mistakes/pitfalls when writing rewrite rules?
- What is a good method for testing and verifying mod_rewrite rules?
- Are there SEO or performance implications of mod_rewrite rules I should be aware of?
- Are there common situations where mod_rewrite might seem like the right tool for the job but isn't?
- What are some common examples?
A place to test your rules
The htaccess tester web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.
Judging by the timestamps on my systems, logrotate does its daily log rotation when logrotate is run by cron. However, if I run it earlier than that it doesn't rotate the files. How does logrotate know if should rotate them or not, does it keep a history or perhaps use timestamps?
How do you disable CPU power management scaling in Windows Server 2008 R2?
After setting the Control Panel, Power Management plan to performance and then rebooting -- CPUID's Cpu-Z still shows the clock speed being scaled.
Does anyone know the steps to verify that a XFS filesystem on top of LVM and md RAID is properly aligned on an array of 4096 Byte aka "Advanced Format" sectored disks?
Some references are:
http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/index.html
http://thunk.org/tytso/blog/2009/02/20/aligning-filesystems-to-an-ssds-erase-block-size/
Also the context of this question is regarding Stack Overflow's new NAS: http://blog.serverfault.com/post/798854017/the-theoretical-and-real-performance-of-raid-10
Is it possible to see in Linux how many read and write requests from user space end up causing cache hits and misses for block devices?
Is there a way to use rdesktop or another Linux client to connect to a server that requires Network Level Authentication?
From Windows Server 2008 R2 -- Control Panel -- System And Security -- System -- Allow Remote Access there is an option that says "Allow connections only from computers running Remote Desktop with Network Level Authentication". So with this enabled I can con not connect from Linux. I can connect from XP but you need SP3 and I had to edit a couple of things in the registry for it to work.
Is there a way to tell rsync to skip its current file while a sync is in progress, maybe by sending it a particular signal?
I already know about ignoring based on patterns, but this would be handy to me sometimes.
As a system administrator, are there things that may not be obvious that should not be done ethically or legally even when instructed to do it? I am more interested in legally, what sort of actions could seriously damage your future carrier or get you in trouble with the law.
For example, is it ever not okay to delete certain types of files even when the Boss requests it?
In particular, I am wondering about the United States. Also, I am not in a situation like this at the moment, another question just got me thinking that this is information I should know.
Really, I am not trying to trigger a discussion of ethics, or complicated scenarios where it would be best to call lawyer. But a checklist, or some literature, or some laws every IT person should know about.
How does logrotate handle open files? Can logrotate rotate files that a process has open?
Does anyone have a ballpark figure of how much VPS ram (without burstable) I would need to have apache with wordpress and subversion as well as the MySQL instance?
Apache would host a couple of sites and SSL. MySQL would have just the Wordpress database. These sites are low traffic, less than 1k hits a day.
This is a Canonical Question about IPv4 Subnets.
Related:
How does Subnetting Work, and How do you do it by hand or in your head? Can someone explain both conceptually and with several examples? Server Fault gets lots of subnetting homework questions, so we could use an answer to point them to on Server Fault itself.
- If I have a network, how do I figure out how to split it up?
- If I am given a netmask, how do I know what the network Range is for it?
- Sometimes there is a slash followed by a number, what is that number?
- Sometimes there is a subnet mask, but also a wildcard mask, they seem like the same thing but they are different?
- Someone mentioned something about knowing binary for this?
I often use telnet or netcat to connect smtp servers to send an email as a test.
Does anyone know how you would send an email using telnet or netcat but attach a file as well? There are probably better ways, but I still want to know :-)
I would be happy with a solution that uses a little bash shell to accomplish the goal, but don't want to use any other tools...
Can anyone tell me what some of the implications of having two different subnets on the same switch would be if VLANs are not being used?