Discuss March 2011

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286 participants
250 discussions

Load balancing...
by Todd 08 Mar '11

08 Mar '11

Hi All, Can anyone help me hash out how best to load balance a website that is getting considerable traffic? In the past I only have experience with BigIP where you have a load balancing device that keeps track and send traffic to the best server possible at the time. This was a proprietary system that I think was something Dell rebranded. Right now, the whole site is is 400gb of video, HTML5, Apache, PHP, MySQL, runs on a single box with 16gb of RAM and mirrored /var/www/html (2x1tb raid level drives). I have a Comcast 50/10 connection, 5 statics and I am seeing about 125 unique visitors a day. The site runs fine, but in anticipation of more traffic as well as a learning experience I would like to load balance. Obviously I need a second server just like the one it is running on now. I will probably spec something out that is capable of 32gb of RAM. What about a dedicated load balancing device? What specs should this be? How much RAM, HD, processor? It is sufficient to buy something with a GB NIC and say 4gb of RAM? Can one go slower but more RAM, small HD? I don't really quite know how intensive a task this decision making process is for the load balancer.. Right now, as example, I have an Untangle Firewall and it runs on a old AMD with 2gb RAM, GB NIC and it seems to do just fine. My local computer store has several P4 2.8ghz with 2GB of RAM for like $99.... Can anyone enlighten me on specs, proper setup, caveats....? -Jason

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Re: [CentOS] Internet connection sharing?
by David Brian Chait 08 Mar '11

08 Mar '11

> Do you have any proof of this? OR are you making assumptions of past > experiences? We have many Windows server on the net, directly with > very few hassles. I have never had a *NIX server under my charge hacked, I have had several Windows machines (those directly connected to the internet) hacked. No, I am not a *NIX worshiper either, I happen to have 7 MS certs. With that said, each OS has stregnths and weaknesses, MS tends to function better as a user facing interface to windows desktop infrastructure, but I avoid it like the plague for public facing infrastructure.

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Race condition with mdadm at bootup?
by Chuck Munro 08 Mar '11

08 Mar '11

Hello folks, I am experiencing a weird problem at bootup with large RAID-6 arrays. After Googling around (a lot) I find that others are having the same issues with CentOS/RHEL/Ubuntu/whatever. In my case it's Scientific Linux-6 which should behave the same way as CentOS-6. I had the same problem with the RHEL-6 evaluation version. I'm posting this question to the SL mailing list as well. For some reason, each time I boot the server a random number of RAID arrays will come up with the hot-spare missing. This occurs with hot-spare components only, never with the active components. Once in a while I'm lucky enough to have all components come up correctly when the system boots. Which hot spares fail to be configured is completely random. I have 12 2TB drives, each divided into 4 primary partitions, and configured as 8 partitionable MD arrays. All drives are partitioned exactly the same way. Each R6 array consists of 5 components (partitions) plus a hot-spare. The small RAID-1 host OS array never has a problem with its hot spare. The predominant theory via Google is that there's a race condition at boot time between full enumeration of all disk partitions and mdadm assembling the arrays. Does anyone know of a way to have mdadm delay its assembly until all partitions are enumerated? Even if it's simply to insert a several-second wait time, that would probably work. My knowledge of the internal workings of the boot process isn't good enough to know where to look. I tried to issue 'mdadm -A -s /dev/md/md_dXX' after booting, but all it does is complain about "No suitable drives found for /dev....." Here is the mdadm.conf file: ------------------------------------- MAILADDR root PROGRAM /root/bin/record_md_events.sh DEVICE partitions ##DEVICE /dev/sd* <<---- this didn't help. AUTO +imsm +1.x -all ## Host OS root arrays: ARRAY /dev/md0 metadata=1.0 num-devices=2 spares=1 UUID=75941adb:33e8fa6a:095a70fd:6fe72c69 ARRAY /dev/md1 metadata=1.1 num-devices=2 spares=1 UUID=7a96d82d:bd6480a2:7433f1c2:947b84e9 ARRAY /dev/md2 metadata=1.1 num-devices=2 spares=1 UUID=ffc6070d:e57a675e:a1624e53:b88479d0 ## Partitionable arrays on LSI controller: ARRAY /dev/md/md_d10 metadata=1.2 num-devices=5 spares=1 UUID=135f0072:90551266:5d9a126a:011e3471 ARRAY /dev/md/md_d11 metadata=1.2 num-devices=5 spares=1 UUID=59e05755:5b3ec51e:e3002cfd:f0720c38 ARRAY /dev/md/md_d12 metadata=1.2 num-devices=5 spares=1 UUID=7916eb13:cd5063ba:a1404cd7:3b65a438 ARRAY /dev/md/md_d13 metadata=1.2 num-devices=5 spares=1 UUID=9a767e04:e4e56a9d:c369d25c:9d333760 ## Partitionable arrays on Tempo controllers: ARRAY /dev/md/md_d20 metadata=1.2 num-devices=5 spares=1 UUID=1d5a3c32:eb9374ac:eff41754:f8a176c1 ARRAY /dev/md/md_d21 metadata=1.2 num-devices=5 spares=1 UUID=38ffe8c9:f3922db9:60bb1522:80fea016 ARRAY /dev/md/md_d22 metadata=1.2 num-devices=5 spares=1 UUID=ebb4ea67:b31b2105:498d81af:9b4f45d3 ARRAY /dev/md/md_d23 metadata=1.2 num-devices=5 spares=1 UUID=da07407f:deeb8906:7a70ae82:6b1d8c4a ------------------------------------- Your suggestions are most welcome ... thanks. Chuck

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Re: [CentOS] CentOS and Marvell SAS/SATA drivers
by Chuck Munro 08 Mar '11

08 Mar '11

On 03/07/2011 09:00 AM, Nico Kadel-Garcia wrote: > > On Sun, Mar 6, 2011 at 10:07 PM, Charles Polisher<cpolish(a)surewest.net> wrote: > >> > https://secure.wikimedia.org/wikipedia/en/wiki/Fakeraid#Firmware.2Fdriver-b… >> > covers fake RAID. > Ouch. That was*precisely* why I used the 2410, not the 1420, SATA > card, some years back. It was nominally more expensive but well worth > the reliability and support, which was very good for RHEL and CentOS. > > I hadn't been thinking about that HostRaid messiness because I read > the reviews and avoided it early. > Here's the latest info which I'll share ... it's good news, thankfully. The problem with terrible performance on the LSI controller was traced to a flaky disk. It turns out that if you examine 'dmesg' carefully you'll find a mapping of the controller's PHY to the "id X" string (thanks to an IT friend for that tip). The LSI error messages have dropped from several thousand/day to maybe 4 or 5/day when stressed. Now the LSI controller is busy re-syncing the arrays with speed consistently over 100,000K/sec, which is excellent. My scepticism regarding SMART data continues ... the flaky drive showed no errors, and a full test and full zero-write using the WD diagnostics revealed no errors either. If the drive is bad, there's no evidence that would cause WD to issue an RMA. Regarding "fake raid" controllers, I use them in several small machines, but only as JBOD with software RAID. I haven't used Adaptec cards for many years, mostly because their SCSI controllers back in the early days were junk. Using RAID for protecting the root/boot drives requires one bit of extra work ... make sure you install grub in the boot sector of at least two drives so you can boot from an alternate if necessary. CentOS/SL/RHEL doesn't do that for you, it only puts grub in the boot sector of the first drive in an array. Chuck

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CentOS 5.x 32bit VPS Ping Issue
by Matt 08 Mar '11

08 Mar '11

I just got an inexpensive VPS too have an outside server to play/test with. I am pinging it every 5 minutes and graphing with MRTG on another CentOS box. This works fine to all servers but the VPS. The first ping to the VPS is always crud and following ones are fine. [root@ns1 scripts]# ping X PING X 56(84) bytes of data. 64 bytes from X: icmp_seq=1 ttl=55 time=773 ms 64 bytes from X: icmp_seq=2 ttl=55 time=42.4 ms 64 bytes from X: icmp_seq=3 ttl=55 time=42.8 ms 64 bytes from X: icmp_seq=4 ttl=55 time=43.1 ms Makes my graph for that one look real bad because it looks at first ping only. Thought about modifying my script to send a warm up ping first but I just don't think I should have to do that or is this a normal thing for a VPS that is pretty much idle?

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what wrong about my ipv6 address
by ann kok 08 Mar '11

08 Mar '11

Hi I used the command "ip -6 addr add 2001:DB8:CAFE:1111::12/64 dev eth0" to add ipv6 address and can see it in ifconfig but can't ping it Why? Thank you # ping6 2001:db8:cafe:1111::12 PING 2001:db8:cafe:1111::12(2001:db8:cafe:1111::12) 56 data bytes >From ::1 icmp_seq=1 Destination unreachable: Address unreachable >From ::1 icmp_seq=2 Destination unreachable: Address unreachable >From ::1 icmp_seq=3 Destination unreachable: Address unreachable >From ::1 icmp_seq=5 Destination unreachable: Address unreachable >From ::1 icmp_seq=6 Destination unreachable: Address unreachable >From ::1 icmp_seq=7 Destination unreachable: Address unreachable >From ::1 icmp_seq=9 Destination unreachable: Address unreachable >From ::1 icmp_seq=10 Destination unreachable: Address unreachable >From ::1 icmp_seq=11 Destination unreachable: Address unreachable

3 3

Enscript
by Hal Davison 08 Mar '11

08 Mar '11

Greetings.. Yes ENSCRIPT is a text to PostScript conversion service. As usual, am a bi confused on how to implement the fit-to-page functionality. Google resources say it is used then proceeds to dance around the issue Using the -f<fontname>@W/H option can one calculate the necessary dimensions for the print job consisting of over 200 pages? --Hal. -- Hal Davison Observe Goal, Set the course, Burn the map Davison Consulting This correspondence was composed using Dragon Speaking Version 10 Peg#: 2007011701

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BUG: soft lockup CPU stuck for 10seconds (Server went down)
by Roland RoLaNd 08 Mar '11

08 Mar '11

Hello, Today my server stopped responding. i went to the console and on the screen there were a continuous loop of the following info shown on the screen: BUG: soft lockup - CPU#0 stuck for 10s! [java:13959] and alot of other information. ii've took a screen shot of the info shown , you can find it under the following url: http://img585.imageshack.us/i/img00012201103070833.jpg/ and had to hard reset for it to be back up and running. i tried googling with no luck for direct relevant info. so hoping you can help out Thanks, --Roland

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email to web posting software?
by Dave Stevens 07 Mar '11

07 Mar '11

Dear CentOS, I have a user group that would like to be able to routinely post (easily) emails to a web site. Must be usable without special training. I have no experience with this. Anyone have a suggestion? LAMP stack installed. Dave -- When a respected information source covers something where you have on-the- ground experience, the result is often to make you wonder how much fecal matter you've swallowed in areas outside your own expertise. -- Rusty Russell

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Centos 6
by JD 07 Mar '11

07 Mar '11

Any word on approximate release date of Centos 6? Cheers, JD

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Discuss March 2011