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Oct
29
revised Should LVM partitions be used in virtual machine images?
add bit about requiring reboot
Oct
29
awarded  Nice Answer
Sep
22
answered How to monitor use of Huge Pages per process
Sep
14
answered Are there alternatives for `dd`?
Sep
14
comment What is the fastest way to send massive amounts of data between two computers?
The specific command in the OP does the compression on the target machine, AFTER it has been transferred over the network. This would be better: dd bs=16M if=/dev/sda | gzip | ssh user@192.168.1.100 'cat - > backup_sda.gz'. Caveats about ssh and compression speed still apply. If you have multiple cores to devote to the task, try pigz instead of gzip.
Sep
14
comment What is the fastest way to send massive amounts of data between two computers?
802.3ad is the open standard that you'd look for on your switches. As a quick hack, though, you might just connect extra NICs to the network, and give them appropriate IP addresses on separate subnets in private address space. (host 1 port a & host 2 port a get one subnet, host 1 port b and host 2 port b get another subnet). Then just run two parallel jobs to do the transfer. This will be a lot simpler than learning the ins and outs of Etherchannel, 802.3ad, etc.
Sep
14
revised What is the fastest way to send massive amounts of data between two computers?
added 11 characters in body
Sep
11
answered What is the fastest way to send massive amounts of data between two computers?
Sep
11
comment What is the fastest way to send massive amounts of data between two computers?
It would potentially improve speed because you would not have to worry about the intermediate network slowing you down. Regarding "typical" vs "crossover" ethernet cables - 1Gb ethernet will auto-crossover as necessary. HP ethernet switches will do this at 100Mb. Other brands, generally not, and you'll need a crossover if you're stuck at 100Mb.
Jul
21
comment Renaming: How to attach a word or rename multiple files
normal grep can handle basic regular expressions - egrep can handle "extended" regular expressions. (Anyone used to perl regexp will find the "extensions" quite sparse - check out pcregrep.)
Jun
11
comment Limit max connections per IP address and new connections per second with iptables
The second rule does NOT work on "new connections". It explicitly affects existing ("ESTABLISHED") connections. To do new connections, you would want --state NEW. You might also consider using -m conntrack --ctstate in place of -m state --state. conntrack is new and improved vs. state.
Jun
11
comment Limit max connections per IP address and new connections per second with iptables
To set this rule for all ports, just remove the --dport 80.
Jun
3
awarded  Excavator
Jun
3
revised Limit max connections per IP address and new connections per second with iptables
remove superfluous "sudo" - should be there twice or not at all. Plus add "this" to get around 6-char limit.
Jun
3
suggested approved edit on Limit max connections per IP address and new connections per second with iptables
Jun
3
comment Limit max connections per IP address and new connections per second with iptables
--syn means that the rule only looks at TCP packets with the syn flag - which means new connections. You could do roughly the same with -m state --state NEW, but this is probably faster.
May
15
awarded  Commentator
May
15
comment What does eno mean in network interface name 'eno16777736' for CentOS 7 or RHEL 7?
It's not always the same, either - I have eno16780032. What a pain in the ass.
Mar
18
comment Do I need swap space if I have more than enough amount of RAM?
(non-transparent) hugepages may not be usable by your app. Typically apps that need tons of memory can use them; e.g., database servers, java jvm. They must be explicitly enabled, and they become a separate memory pool that can't be used for other purposes. THis may be good or may be bad, depending on your circumstances. Also, learn about Transparent hugepages. These attempt to move things around so that you're using hugepages (for their performance improvement) even though your apps don't know how. If memory is fragmented things can go south as the hugepage sweeper has more to do.
Mar
18
comment Do I need swap space if I have more than enough amount of RAM?
One downside - imagine that your disk storage is slow. I'm thinking of a case where I had a vmware installation with VM storage on an ISCSI SAN. SAN was connected via 1GE. We had plenty of IOPS but not a ton of bandwidth. If a VM started swapping heavily due to a runaway application, the only reasonable course of action was usually a hard reboot - it was so slow to get logged in, and the server was hosed anyway. We changed things so that we had small swap partitions, and let the OOM killer take over much sooner.