The io tag has no wiki summary.
-2
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0answers
28 views
What is the advantage of interrupt-driven input/output? [closed]
I just took an online quiz for my Operating Systems class. I got this question wrong, can you please give the right answer and why? I answered D. Also, if this needs to be migrated to a different SE ...
0
votes
1answer
47 views
configuration for max read throughput on ssd: pcie vs sata vs raid
I'm looking to configure a storage setup, using ssd's, that will deliver the fastest read throughput on large (2+ GB) files on a 24 core (12 physical core) system.
The data is static for the most ...
3
votes
2answers
119 views
Why does a CP command on linux consume CPU?
I just run a copy command for two large directories with a small number of huge files and I see my cp process is consuming around half a core in top:
51116 root 20 0 110m 876 688 D 43.9 ...
0
votes
3answers
38 views
Resource monitor and how to spot if you have disk I/O problems?
I have an application server which runs pervasive SQL and app using it.
Last weeks the users are complaining about poor performace of the app and I suspect disk I/O problems because CPU and RAM ...
0
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2answers
50 views
wait rate very high due to mysql server activity
Sometimes the server is very slow and needs a lot of time for serving the requests. iotop shows a disk read rate of 1-2 M/S on average for some minutes (which is not that much actually), after that ...
2
votes
2answers
169 views
Is there a way to delete 100GB file on Linux without thrashing IO / load?
I have a huge log file I need to delete on a production web server. I'm worried it'll bring the system to a crawl if I rm it on Linux. Any brilliant ideas?
Update:
Filesystem: ext3
Partition: /var ...
1
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0answers
49 views
How to identify which processes are waiting for I/O? [closed]
Possible Duplicate:
Linux - How can I see what's waiting for disk IO
top shows that plenty of time (98%) is spent in waiting for I/O (WA). What is the best way to identify the ...
6
votes
2answers
149 views
Logging hurts MySQL performance - but, why?
I'm quite surprised that I can't see an answer to this anywhere on the site already, nor in the MySQL documentation (section 5.2 seems to have logging otherwise well covered!)
If I enable binlogs, I ...
0
votes
2answers
184 views
Is a 'high' IO rate healthy?
I do a lot of work with my Linode that currently hosts a site, but every now and then (usually once every two months or so) - I'll get a warning about my IO rate being too high (Usually just higher ...
0
votes
4answers
217 views
Reducing IO caused by nginx
I have a lot of free RAM but my IO is always 100 %util or very close. What ways can I reduce IO by using more RAM? My iotop shows nginx worker processes with the highest io rate. This is a file server ...
0
votes
1answer
52 views
Delay before download starts when serving files using nginx
I am currently using nginx to serve downloads off my website. Users sometimes need to wait about 5 seconds before their download starts after clicking a download link. I'm not sure if I need to start ...
0
votes
2answers
70 views
Try to delete files used by IIS
I got a service coded in c# whoes deleted somes web site files hosted on iis, before an update. But sometime when i delete the files, they stay there.
If I try to delete them manually, via explorer, ...
0
votes
3answers
98 views
DB Server Disk I/O utilization
I have a Linux server that I use to run the DB of my application (MySql), the server have 8GB Ram and 4 cores.
there are no other applications running on the server besides the MySql.
Most of the ...
4
votes
1answer
219 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. ...
1
vote
0answers
245 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
133 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
179 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
52 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
2answers
337 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 ...
3
votes
2answers
125 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
83 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
75 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
276 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, ...
4
votes
1answer
92 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
88 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 ...
1
vote
1answer
207 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 ...
2
votes
1answer
43 views
Is the XP VMM a bottleneck on a multi core machine?
I have a dual Xeon hex core machine running an IO intensive application. (WinXP 32) I am seeing a hardware driver (1/2 user mode, 1/2 kernel, streaming data) that is using 6k delta page faults per ...
1
vote
1answer
197 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
157 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 ...
0
votes
1answer
294 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 = ...
1
vote
1answer
68 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 ...
0
votes
1answer
54 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
218 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
140 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
225 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 ...
1
vote
2answers
330 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
112 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?
3
votes
1answer
196 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
168 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
...
0
votes
1answer
126 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
132 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
103 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 ...
0
votes
0answers
44 views
Prevent cache trashing or is this disk broken?
We are in the process of moving away from our old host and going to a cloud-based system like EC2. However, we still have a production system keeping everyone happy until then. Today I ran a simple ...
0
votes
4answers
2k 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
255 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:
1. changing disks to new disks ...
1
vote
3answers
91 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 ...
0
votes
3answers
471 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
221 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
140 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.
...
34
votes
11answers
2k 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 ...
