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Apr
25
comment How to capture ack or syn packets by Tcpdump?
Maybe you're not troubleshooting TCP. Maybe you want to see how chatty a program is, and you want to count its outbound connections. Like me, now.
Apr
13
comment Why drop caches in Linux?
Caching aggressively is a win. Caching so aggressively that your application starts to swap...not so much.
Apr
12
comment Why drop caches in Linux?
"its possible that though your application may not be using these RAM but Linux is caching aggressively into its memory and even though the application needs memory it wont free some of these cache but would rather start swapping." Not very specific. In practice, memory management isn't perfect, and having a knob to turn when that imperfection shows up is a good thing.
Apr
11
comment when and how to appropriately use /proc/sys/vm/drop_caches
It can be useful to reduce memory fragmentation. SUSE recommends it to attempt to relieve memory pressure: suse.com/communities/blog/…
Apr
11
comment Why drop caches in Linux?
SUSE recommends this method to try to deal with memory pressure. suse.com/communities/blog/…
Mar
28
comment NTP synchronized clock alongside the system clock
I'm with MadHatter, but assuming you really need this...If you don't need to query the time very often, you could just do an ntpdate to a remote host to get the "real" time when you need to write logs. If your realtime system has a precise clock, but you don't want to sync it to the real time, you could compare the local time to the realtime at boot time, and store the offset. Then use that stored offset when writing the log messages.
Mar
28
comment Linux memory fragmentation
According to the fine manual, "Huge pages cannot be swapped out under memory pressure." I think this is a good answer in w/r/t standard memory but not for hugepages.
Mar
26
awarded  Necromancer
Mar
24
comment Apache caching old configuration?
No, if you did a full restart you can ignore that concern. Seems though that you must have either a config being used you aren't expecting, or perhaps an entirely different httpd binary. Ensure that the httpd binary you are running is the one you think it is (poke around in /proc, use lsof, etc). Ensure that it really did get restarted (with ps).
Mar
23
comment Apache caching old configuration?
Did you "gracefully" restart apache? Sometimes it doesn't really reconfigure everything when you do that.
Mar
17
comment Does an NFS client incur read/write page faults proportional to bytes read to/written from server?
These seem relevant: gossamer-threads.com/lists/linux/kernel/… serverfault.com/questions/270283/… . the words "from disk" are used to describe the statistics you're looking at.
Mar
17
comment What does the fields in sar -B output mean?
working link to gossamer-threads gossamer-threads.com/lists/linux/kernel/…
Mar
17
comment Does an NFS client incur read/write page faults proportional to bytes read to/written from server?
Stuff read from the NFS server may have fit in cache, but certainly writes should make something happen. I'm not sure, but my guess is that the NFS operations are not considered page faults.
Mar
16
revised How can one efficiently use S3 to back up files incrementally?
add link to doc page for aws s3 sycn command
Mar
16
comment How can one efficiently use S3 to back up files incrementally?
I believe you that it doesn't work, but the docs say "A local file will require uploading if the size of the local file is different than the size of the s3 object, the last modified time of the local file is newer than the last modified time of the s3 object, or the local file does not exist under the specified bucket and prefix." Make sure you have the latest version of aws-cli - if you can reproduce this, file a bug with them on github. They were responsive when i filed a bug a while ago.
Mar
4
comment I've inherited a rat's nest of cabling. What now?
Monoprice is cheap but i've had quality problems with items bought from them. CDW has pretty cheap prices on their house brand cables, which I believe are made by Belkin. I'm sure there are other inexpensive vendors.
Mar
4
comment I've inherited a rat's nest of cabling. What now?
I really like your idea of mid-span cable labels. I always label both ends of each cable with a serial number and the length. Having the length labeled is handy when you're reaching into the cable box. I use a Brady ID Pal cable label maker. Be sure to get the "industrial" label tape -it actually sticks more or less permanently, unlike typical label maker tape.
Mar
1
revised How to change vCenter server appliance IP from command line?
worked in the string VCSA as search bait, fixed a couple typos
Mar
1
suggested approved edit on How to change vCenter server appliance IP from command line?
Feb
19
comment Can you help me with my capacity planning?
The thing that I've seen undersized most often in VM implementations is disk I/O. Most people understand disk space, CPU speed, and memory. They forget about that disk performance.