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I've been trying to do traffic shaping on one of my public servers and after reading up, it seems like the way to do so is via tc/htb. However, most of the documentation seems at least half a decade old with nothing new recently. Furthermore, trying to get documentation on tc filters turned up a blank. man tc refers to a tc-filters (8) but trying to man that gives a no such page/section

I've been reading that it's possible to set up a system with multiple NIC to provide redundant internet connectivity such that it will switch to a secondary connection if the primary ISP fails. Is it possible in a similar way to setup redundant LAN routing? I read that it is possible to aggregate/bond multiple NIC to stackable switches that support link aggregation and redundancy. But if

I'm trying to figure out what's causing an average system load of 3+ to 5+ on an Intel quad core. The server has with 2 KVM guests (assigned 1 core and 2 cores) that's lightly loaded (0.1~0.4) each. Both guest/host are running 64bit CentOS 5.6 Originally I suspected maybe it's i/o but on checking, there is very little i/o wait % as well. Plenty of free disk space available on all

I'm trying to resolve an I/O problem on a CentOS 5.6 server. The process basically scans through Maildirs, checking for space usage and quota. Because there are hundred odd user folders and several 10s of thousands of small files, this sends the I/O wait % way high. The server hits a very high load level and stops responding to other requests until the crawl is done. I am wondering if I add

I was trying to do some performance testing between using iSCSI on the host as a diskfile to a guest vs the VM guest using the iSCSI device directly. However, in the process of trying to establish a baseline performance figure, I started increasing the MTU settings on the PCI-express NICs with RTL8168B chips. First bottleneck was discovering the max MTU allowed on these is 7K instead of 9K but

In a moment of epic stupidity, having ran out of space on the root partition of a server due to /var chewing up the space, I added a separate drive for the purpose of mounting it as /var To do so, I mounted the new drive as /var2, cp -R (in hindsight should had rsync to preserve attributes), deleted the original /var to free up space, edited fstab and rebooted... unsurprisingly to a fubar'd

I was having problems with the same server locking up to the point I can't even get in via SSH. I've already used HTB/TC to reserve bandwidth for my SSH port but the problem now isn't an attack on the bandwidth. So I'm trying to figure out if there's a way to ensure that SSH is given cpu and i/o priority. However, so far reading seems to imply that it's probably not going

Might be slightly OT as it isn't necessarily a CentOS related issue. I've been using WD Reds as mdraid components which worked pretty well for non-IOPS intensive workloads. However, the latest C7 server I built, ran into problems with them on on a Intel C236 board (SuperMicro X11SSH) with tons of "ata bus error write fpdma queued". Googling on it threw up old suggestions to

Has anybody tried or knows if it is possible to create a MD RAID1 device using networked iSCSI devices like those created using OpenFiler? The idea I'm thinking of here is to use two OpenFiler servers with physical drives in RAID 1, to create iSCSI virtual devices and run CentOS guest VMs off the MD RAID 1 device. Since theoretically, this setup would survive both a single physical drive

I'm trying to setup a very small system intended for doing monitoring/logging. It's done on an Intel Atoms in a small box and the idea was to simply run it off a pair of USB flash drives in software RAID 1. Now the problem is that while the 6.2 DVD installer could go through the entire install process, grub will load then just stop at the prompt. The system will work if I use a SATA hard

Which of these would be the recommended virtualization platform for mainly CentOS guest on CentOS host for running a virtualized mail server? From what I've read, objectively it seems that VMWare's still the way to go although I would had like to go with Xen or KVM just as a matter of subjective preference. VMWare's offering seems to have the best support and tools, plus likely the

After successfully getting higher MTU to work on my Realtek NICs, I started testing the impact of higher MTU on file transfers using NFS exported ramdisk to ramdisk. The results were unexpected. The higher the MTU on the sending NIC, the lower the file transfer speed. I tested by using time cp to copy a 1GB file (In case compression might affect the results, so I dd the test file from the CentOS

Is it possible or will there be any problems with using mdraid on top of mdraid? specifically say mdraid 1/5 on top of mdraid multipath. e.g. 4 storage machines exporting iSCSI targets via two different physical network switches then use multipath to create md block devices then use mdraid on these md block devices The purpose being the storage array surviving a physical network switch

I've been leaning towards actually deploying gluster in one of my projects for a while and finally a probable candidate project came up. However, researching into the specific use case, it seems that gluster isn't really suitable for load profiles that deal with lots of concurrent small files. e.g. http://www.techforce.com.br/news/linux_blog/glusterfs_tuning_small_files

I'm wondering if virtualization could be used as a cheap redundancy solution for situations which can tolerate a certain amount of downtime. Current recommendations is to run some kind of replication server such as DRBD. The problem here is cost if there are more than one server (or servers running on different OS) to be backed up. I'd basically need to tell my client they need to buy say

I'm having problems trying to install CentOS as a KVM guest despite following the wikis and howtos. The problem is that most of the instructions skip the part that happens after virt-install... It seems that something blindingly obvious happens if nothing goes wrong and most instructions continues from the OS installation screen. However, when I try this, I get a blank console that says

I was trying to get a new Canon laser printer LBP-7110CW to work with a CentOS 6 machine. It already has an older Canon multi-function laser MF-4720W which worked fine. Both printers are connected via wireless. The new printer works fine from a Windows machine. The web-based GUI can be accessed from the C6 machine without problem either. However, CUPS cannot "discover" the printer when

On 03/01/2016 09:53 AM, Emmanuel Noobadmin wrote: > > Since I'm likely to use Reds again, it is a bit of a concern. So > wondering if I just happen to get an unlucky batch, or is there some > incompatibility between the Reds and the Intel C236 chipset, or > between Red / C236 / Centos 7 combo or the unlikely chance WD ha...

On 3/1/2016 9:53 AM, Emmanuel Noobadmin wrote: > However, the latest C7 server I built, ran into problems with them on > on a Intel C236 board (SuperMicro X11SSH) with tons of "ata bus error > write fpdma queued". Googling on it threw up old suggestions to limit > SATA link speed to 1.5Gbps using libata.force boot o...

Emmanuel Noobadmin wrote: > Might be slightly OT as it isn't necessarily a CentOS related issue. > > I've been using WD Reds as mdraid components which worked pretty well > for non-IOPS intensive workloads. > > However, the latest C7 server I built, ran into problems with them on > on a I...