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I don't understand why a top report shows such a high server load. I've even turned off httpd for 5 minutes since that seemed to be a large part of the loading I was seeing yesterday. I posted in another topic about hdb dma entries in my logs, but I was at least able to lower the load to 0.5 when I turned off httpd
Yes I'm going to say the problem is with the disk access.
I have my server setup using Ensim Webppliance using a dual HD config. Everything to do with the virtual hosting is on /dev/hdb in the /home directory and everything else is on /dev/hda
I was getting I/O errors on hdb and bad sectors and we decided to change it out because I kept getting corrupt MySQL tables which is just bizarre. After replacing the drive we couldn't bring up the server..it would just hang in the boot process. We could put both drives into a similar 1U server and it would come up. So we replaced the mobo and then it would come up.
So the server has been running since Wed 7:45 pretty well. But on Saturday am I saw some dma time out errors on hdb. The server loading would just peg. I turned off httpd service and it would come down, but never did the ram useage. Since all virtual hosting is on /home I believe the server loading is due to the disk write/read speed on hdb.
Last night I also ran another script that does mass emailing (legite newsletter) and it just crawled. So I checked the disk read speed..
[root@startbox log]# hdparm -t /dev/hdb
Timing buffered disk reads: 2 MB in 10.28 seconds = 199.22 kB/sec
and its doing this set as (which my colo support told me to run it as)...
Ok, I see top finally has me using some SWAP..but I see my disk read speed drops way off!! Knowing it was doing 2-8MB/sec earlier today before swap use..this seems like a big drop in performance?
Do I need more RAM? The new mobo has a 3rd slot for RAM where the old mobo had only 2. My server loading is still ok, but this slow drive speed is going to kill me especially with the MySQL reads/writes.
Maybe I should switch the priority on swap to hda5 and give this drive a break?
[root@startbox html]# hdparm -t /dev/hdb
Timing buffered disk reads: 4 MB in 4.16 seconds = 984.62 kB/sec
I have a Maxtor drive and sometimes if I leave my computer on for over 16 hours. The drive starts acting up. The drive sometimes complains that it does not see /home, so I have to re-mount /home. My /home partition does not have any problems. I do not have any DMA problems with it. After I enabled no write error through hdparm, I think it fixed the problem. You can try it but do it with caution.
I read that Maxtor drives do not like to be on the same channel as other drives. Try to put the Maxtor drive on its own channel. By placing the Maxtor on another channel. Swap can work in parallel, so it does not have to fight with other hard drives on the same channel.
For databases, use a SCSI controller with expandable cache. A lot of cache works well with databases. Hard drives with built-in 8 megabytes of cache are a waste when used on the controller with its own cache.
If you want reliability use either SATA or SCSI hard drives.
You probably want to stop using ntpd. It can bogged down the server. Use a seperate system for ntpd. Also usb storage devices can bogged down the system because they depend on about 70% to 80% of the CPU. Use usb storage another system and then copy the files that you want backup or restore the files.
It could be something is conflicting with other pieces of hardware in your system. Try taking out one component at a time. You may want to run memtest86.