The io tag has no wiki summary.
5
votes
1answer
685 views
5.5GB written daily to 1.2GB root volume - 4 times previous levels
Problem:
I recently revamped one of my servers, it was tested prior to use, and functions well, however, a few days ago, I noticed approximately 4 times the usual amount of writes to the root volume. ...
2
votes
1answer
1k views
High disk I/O activity in CentOS server
I have about 16 websites in a CentOS dedicated, and I am having some problems on high traffic hours, it seems to be a high disk I/O activity causing a general slowdown.
I've installed atop and this ...
0
votes
1answer
355 views
How to track a single Xen VM's I/O utilization
What is a good way to monitor I/O individually for Xen Virtual Machines (not Dom0)?
0
votes
1answer
409 views
IO utilization percent of 4920.45% - iostat -x , What's wrong?
I have seen wrong percent use of a disk IO some times on servers that have been a long time without reboot.
By any means this server has significant IO. Tonight it'll be rebooted and I'm sure ...
1
vote
2answers
128 views
How to analyze system calls when your disk is in read only and strace output is “Bus error”?
We have a HW problem with the disks, that made all the mount points to be read only. Output of dmesg:
end_request: I/O error, dev sda, sector 15574609
sd 0:0:0:0: SCSI error: return code = 0x00040000
...
4
votes
3answers
2k views
Utility for Monitoring IOPS on servers
We recently ran the Dell Performance Analysis Collection kit which monitors your servers via WMI for 24 hours. You send the file off to Dell and they return a report with graphs of IOPS and MB/S disk ...
4
votes
2answers
189 views
/etc/passwd continually accessed
I'm running a server on EC2 (Cent OS, 2.6.35.14, x86_64), and I recently went over my 1 million I/Os per month quota, which is absurd, as my disk utilization shouldn't be anywhere near that. (I'm not ...
1
vote
1answer
161 views
Good SAN sequential I/O throughput
We have an EMC San - CX4-240C filled with 15k (4Gb) Fibre Channel disks setup in RAID 5. Our applications that run on this SAN do primarily Sequential read and write of large text data files. I'm ...
0
votes
2answers
133 views
Possible disk IO problem. Help to be sure.
Since some time days ago, one of my servers started crashing. Currently it is crashing almost every day. Sometimes, over once a day. Only a restart can solve.
The last time the problem happend, the ...
9
votes
2answers
671 views
How does Linux handle concurrent disk IO?
When a Linux server is serving many concurrent requests to read many different files, does it:
Seek to File_1, read the entire file, then seek to File_2, read the entire file, then seek to File_3, ...
5
votes
1answer
374 views
Maximizing throughput of virtual file systems
I've been using a QEMU system to build software. The problem I've been having is that the system seems to suffer from extremely slow disk access. This is not necessarily a problem as it's not really a ...
1
vote
1answer
198 views
Does DFS-R actually write 100%+change to a file on the receiving server(s)?
I am analyzing DFS-R on Windows 2003 R2 and have come across a horrendous thing.
It appears that when you append a small amount of data to a large (existing) file, the write cost on the server for ...
2
votes
1answer
709 views
Monitorig ZFS io with Zabbix
I need to monitor per-zpool IO stats (number of reads, number of writes, size of reads, size of writes) with Zabbix. Is there a script for that?
kstat provides only agregate data (all zpools summed ...
1
vote
1answer
497 views
iotop for Linux kernel 2.6.18
So it has to come to my attention that iotop isn't availalbe for 2.6.18 since it's less than 2.6.20 and requires Python 2.6+. I've done some research and came across this article:
...
0
votes
1answer
232 views
IO Speed virtual image vs Physical?
I am planning on building a Continuous Integration Server (the existing one is too slow). My plan is to run multiple OSes for our application testing on KVM.
The structure will be a single physical ...
1
vote
1answer
2k views
kernel: scsi 0:0:0:0: rejecting I/O to dead device
Yesterday, OSSEC sent me an alerting email:
Jul 29 21:25:16 SVR4149 kernel: end_request: I/O error, dev sda, sector 334634969
Jul 29 21:25:16 SVR4149 kernel: sd 0:0:0:0: SCSI error: return code = ...
2
votes
1answer
169 views
inonice not working properly in xen dom0
I have a Xen Dom0 (3.2) with a bunch of domUs (paravirt). DomU VBDs are on local LVM volumes. Now I want to get backups of the LVM volumes using snapshots. I use rsync ioniced to idle (ionice -c3).
I ...
1
vote
1answer
399 views
IO and bus errors on Ubuntu Server
I've got an old computer running Ubuntu Server 10.04, which acts as router, file server and web server. A couple of weeks ago I inserted a PCIe video card, since the motherboard did not have any video ...
3
votes
2answers
775 views
In Windows Task Manager, in the Processes tab, what does I/O Other mean?
In Windows Server 2003, I'm seeing a process in Task Manager with a high value in the I/O Other column. I'm trying to determine if it's in some kind of error state, but I don't know what I/O Other ...
6
votes
1answer
437 views
using temporary files vs pipes advantages and disadvantages
say I have a file named jobs.csv
and I would like to get the top 50k jobs done by Foo
I can either do:
# cat jobs.csv | sort -u | head -n 50000 > /tmp/jobs.csv
# cat /tmp/jobs.csv | while read ...
11
votes
2answers
642 views
How do you monitor the performance of a character device (e.g. tape drive)?
There are many ways to monitor block device performance: dstat and iostat, heck, even sar will give you data on block device I/O rates. Unfortunately, I don't know of any good spur-of-the-moment ...
2
votes
2answers
1k views
Monitor Disk I/O Using DD
I've bee looking into the possibility that my server is experiencing a lot of iowait issues. I've found a lot online about running the dd command. I am unable to run this conv:
[root@vps ~]# dd ...
1
vote
1answer
827 views
On Solaris, how can I tell what processes are doing disk i/o on a particular device?
On Solaris, iostat tells me that a device is 92% busy, but how do I find out what programs are making the requests?
6
votes
2answers
575 views
How to set i/o priority for nfs client processes?
The configuration is: A linux server and a nas box (netgear) acting as nfs server.
It is easy for a single process on the linux server to use all i/o bandwidth by simply copying a file from the nfs ...
0
votes
1answer
519 views
What do the output values of dstat command mean when monitoring IO?
I am monitoring the IO and SWAP usage of a process in my backup server. I executed dstat -rs 5 and this was an example output:
--io/total- ----swap---
read writ| used free
92.0 57.3 |3228k 514M
...
1
vote
1answer
388 views
Ramdisk vs Build-In IO Caching on Windows
I'm trying to understand the built-in IO cache on Windows. If an application writes to a file, and then reads/writes it multiple subsequent times, it seems that the IO cache should allow this to ...
0
votes
4answers
416 views
How can I get a list of Programs doing Disk IO?
I have a server (running CentOS 5) and I need to figure out which programs (MySQL, Apache, etc) are doing the most Disk I/O? Is there a command that will allow me to calculate an average over time?
2
votes
2answers
198 views
comparing disk performance of machines
I am in the process of moving applications running on old Linux machines onto VMs. As part of this, I need to justify the VMs have at least the capacity (i.e. CPU speed, RAM, disk, disk speed, network ...
3
votes
4answers
10k views
How to measure IOwait per device?
I have a server, which exports home directories over NFS. They are on software RAID1 (/dev/sdb and /dev/sdc) and the OS is on /dev/sda. I noticed that my %iowait as reported by top and sar are ...
1
vote
2answers
690 views
Dell PE2950 - slow IO rates for writing and reading locally
I'm having a serious issue with dell server PE2950. The server has really slow IO rates, so slow that I'm not able to use it anymore
I tried few things to solve this:
changing disks to new disks ...
1
vote
3answers
147 views
Benchmarking a hard disk drive for OLTP
I have a PostgreSQL database (OLTP, 10GB in size) server and I'm planning an array of hdds for it's storage. I have various disks I can use. I need to find the best ones for the job with the right ...
1
vote
3answers
994 views
NFS IO priority on ZFS/Solaris
I've got a Nexenta/ZFS NAS that I'm using as an NFS backing store for a small VMware vSphere farm. At the moment I have 9x1TB disks all mirrored (last disk is configured as a write log device).
The ...
3
votes
1answer
399 views
Measuring Disk IO programmatically
I want to measure some numbers related to disk io in a given timespan, programmatically. This means I don't want to spawn a process like iostat to get my numbers, by prefer to read something from proc ...
1
vote
5answers
294 views
Scratch files in /tmp getting mysteriously deleted
I have certain files in a /tmp subdirectory that a script I wrote uses for scratch. The opens and closes these file perfectly fine for a few hours. Then, out of nowhere, the files are no longer found.
...
49
votes
13answers
7k views
Are networks now faster than disks?
This is a software design question
I used to work on the following rule for speed
cache memory > memory > disk > network
With each step being 5-10 times the previous step (e.g. cache ...
2
votes
3answers
5k views
Determine what's causing high disk IO
I'm having a problem with my VPS and disk IO. My server is running nginx + PHP-FPM + APC. The database is located on another dedicated VPS. I have several Wordpress MU sites living on the web server. ...
1
vote
2answers
659 views
High Disk I/O rate. How to investigate
One of my servers is getting very high Disk I/Os. The problem is that the disk I/Os are constantly increasing. The server just have simple LAMP configuration and there shouldnt be any disk operation ...
4
votes
3answers
1k views
Measuring 'total bytes written' under Linux
We're quite interested in exploring the possibility of using SSD drives in a server environment. However, one thing that we need to establish is expected drive longevity. According to this article ...
3
votes
3answers
1k views
High Load - Low IO - Low CPU usage
I have a system whose load is rather high. As you can see from the top output below, CPU usage and I/O is negligible:
top - 17:31:59 up 4 days, 2:34, 2
users, load average: 1.00, 0.99, 1.00
...
1
vote
2answers
2k views
VMWare Esxi Looking for Bottlenecks
I have a VMWare ESxi box, 22GB ram, Dual Quad Core Xeon, 2 Sas drives + Write caching raid controller etc.
Anyways, have about 30 small XP VM's running on it and starting to get some very slow boot ...
0
votes
3answers
333 views
How to view formatted iotop log file in terminal with a cat
Hey there.
So I have logged the history of Disk usage with a iotop > iohis.log
How can I view the file so it is formatted nicely and I can actually find the issue.
I thought I could use the cat but ...
0
votes
3answers
196 views
Estimate daily network IO between 2 servers
I have 2 servers : a database server (SQL Server 2008, called server A) and an application server (called server B) which send SQL queries to the first one.
They are actually in the same LAN, but we ...
0
votes
0answers
50 views
Determining Performance Limits
I have a number of windows processes that pass messages between them hat a high rate using tcp to local host. Aside from testing on actual hardware how can I assess what my hardware limit will be.
...
2
votes
2answers
297 views
How do I know if my disks are being hit with too many I/O reads or writes or both?
I know a bit about disk I/O and bottlenecks relating to this especially when relating to databases.
How do I really know what the max I/O numbers will be for my disks? What metric might be available ...
0
votes
5answers
10k views
I/O Performance Benchmarking Linux
Just finished setting up a poor mans SAN with iSCSI and want to benchmark it. What are some good I/O performance benchmarks for Linux besides:
hdparm -tT /dev/sda1
How do I get a IOPS measurement?
...
1
vote
1answer
448 views
IO-related lockups on a Xen PV guest running Ubuntu 10.04
I have a Xen PV guest, running Ubuntu 10.04. I do not run the underlying host. Kernel is the stock one provided by Ubuntu:
Linux nephos 2.6.32-21-server #32-Ubuntu SMP Fri Apr 16 09:17:34 UTC 2010 ...
10
votes
1answer
8k views
Determining which process is causing heavy disk I/O?
I've seen this question:
How to identify heavy write to disk?
And I've used dstat and atop before...but they don't seem to pinpoint what process is causing disk I/O. For example, from dstat:
dstat ...
5
votes
2answers
2k views
Will adding a SSD cache device to my ZFS storage improve performance?
The server has 4GB of RAM and my zpool is made up of 15.5k SAS drives arranged like this:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz1-0 ...
0
votes
1answer
284 views
Can I set noatime for my XEN guest OS partition? Will it work?
I have a VPS in cloud environment based on XEN Virtualization platform.
/etc/fstab looks like that:
LABEL=PRGMRDISK1 / ext3 errors=remount-ro 0 0
As far as I know IO can pretty ...
3
votes
7answers
3k views
How do I tell which processes are writing heavily to disk in CentOS 5?
Our server started getting slow, so I ran iostat on it.
iostat -dx 5
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 ...
