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Hi All,
I have a mail/dns/web server that has been having some perfomance issues. Little things will make the load average spike, the system becomes slow and my mail server starts erroring out and won't recover itself.
The latest thing that seems to be causing the trouble is the nightly updatedb. CPU util seems fine, mem seems fine, so I'm assuming it has something to do with disk IO. Here are some outputs, normal load avg. is about 2. Usually when this is running I'll get a load of about 15, for some reason, it only went up to about 11 this time
Running Kernel 2.4.31 on Slackware. Running RAID5 on a mylex acceleraid 352.
Code:
***** DAC960 RAID Driver Version 2.4.11 of 11 October 2001 *****
Copyright 1998-2001 by Leonard N. Zubkoff <lnz@dandelion.com>
Configuring Mylex AcceleRAID 352 PCI RAID Controller
Firmware Version: 6.00-15, Channels: 2, Memory Size: 32MB
PCI Bus: 2, Device: 1, Function: 0, I/O Address: Unassigned
PCI Address: 0xFC000000 mapped at 0xF898E000, IRQ Channel: 24
Controller Queue Depth: 512, Maximum Blocks per Command: 2048
Driver Queue Depth: 511, Scatter/Gather Limit: 128 of 257 Segments
Physical Devices:
0:0 Vendor: IBM Model: DDYS-T36950N Revision: S80D
Asynchronous
Serial Number: 4FY0X646
0:4 Vendor: IBM Model: IC35L036UWD210-0 Revision: S5BS
Wide Synchronous at 40 MB/sec
Serial Number: KQZX2556
Disk Status: Online, 71651328 blocks
0:7 Vendor: MYLEX Model: AcceleRAID 352 Revision: 0600
Wide Synchronous at 160 MB/sec
Serial Number:
0:8 Vendor: IBM Model: IC35L036UWD210-0 Revision: S5BS
Wide Synchronous at 40 MB/sec
Serial Number: 52Y0T615
Disk Status: Online, 71651328 blocks
0:12 Vendor: IBM Model: IC35L036UWD210-0 Revision: S5BS
Wide Synchronous at 40 MB/sec
Serial Number: 52Y0Y219
Disk Status: Online, 71651328 blocks
1:4 Vendor: IBM Model: IC35L036UWD210-0 Revision: S5BS
Wide Synchronous at 40 MB/sec
Serial Number: KQZX2544
Disk Status: Standby, 71651328 blocks
1:7 Vendor: MYLEX Model: AcceleRAID 352 Revision: 0600
Wide Synchronous at 160 MB/sec
Serial Number:
1:8 Vendor: IBM Model: IC35L036UWD210-0 Revision: S5BS
Wide Synchronous at 40 MB/sec
Serial Number: KQZX2484
Disk Status: Online, 71651328 blocks
1:12 Vendor: IBM Model: DDYS-T36950N Revision: S80D
Wide Synchronous at 40 MB/sec
Serial Number: 4FY0Z227
Disk Status: Online, 71651328 blocks
Logical Drives:
/dev/rd/c0d0: RAID-5, Online, 286605312 blocks
Logical Device Initialized, BIOS Geometry: 255/63
Stripe Size: 64KB, Segment Size: 8KB
Read Cache Disabled, Write Cache Disabled
No Rebuild or Consistency Check in Progress
Truthfully, I'm not even sure what utilites to use to check out IO performance. A lot of what I found through google isn't available on this Slackware machine.
Got any advice on where I can start to troubleshoot the performance issues?
The first thing I see is memory usage being topped out. What is running that is using 2gb of RAM? You are entering swap, which is typically a system killer.
Didn't see anything related to IO in the logs. Especially anything that looked like an Error.
Quote:
why the updatedb every night ???.
No reason really, like you said, just the done thing. I do use the locate command quite a bit, as I'm still learning. And really, it's not just updatedb that's causing me problems.. just general performance issues. While running a back up to a tape, we sometimes see the same thing.
I installed the sysstat package. Unfortunately, iostat isn't showing me much I don't think. Maybe because of the kernel version... I'm not sure. Here is some output though:
Code:
root@mailgate:/dev# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/rd/c0d0p1 130633552 51940180 71725180 43% /
Normal utilization IOSTAT:
root@mailgate:/dev# iostat -x c0d0p1 5
Linux 2.4.31 (mailgate) 03/09/06
avg-cpu: %user %nice %system %iowait %steal %idle
1.22 0.00 1.67 0.00 0.00 97.11
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util
(notice all device stats are blank, I've also tried /dev/rd/c0d0p1 and rd/c0d0p1 as devices for iostat)
IOSTAT while running updatedb. Load AVG about 14. Not much different:
root@mailgate:/dev# iostat -x c0d0p1 5
Linux 2.4.31 (mailgate) 03/09/06
avg-cpu: %user %nice %system %iowait %steal %idle
0.45 0.00 0.30 0.00 0.00 99.25
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util
Also tried this, and gave me no data:
root@mailgate:/dev# iostat -d 5
Linux 2.4.31 (mailgate) 03/09/06
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
Never really looked at a 2.4 kernel from a performance aspect - even on Slack the first thing I did was go 2.6.
If you get the kernel sources with Slack (I don't have any Slack now so I can't check), have a look at iostats.txt - else go look online. Has a good discussion on fields in /proc - there are differences between 2.4 and 2.6. Maybe you can knock up a script to pull the numbers direct from there and write them to a file to have a look at later.
One would think your problem has to be I/O. I had skipped the fact you are running RAID5 - wonder if that's getting in the way. From Linux point of view, you only have one disk - including swap, which generally isn't a good idea. So it will be trying to manage the I/O based on that - merging I/O and calculating swap slot locality.
Your raid card will then be tearing it all apart and spraying it all over the disks. Hardly working together for optimal performance - not that that was ever a promise of RAID5.
Maybe in the bad periods you could looks for tasks in I/O wait - (reverse) sort "top" on the "S" field (look for status "D").
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