0
votes
0answers
26 views

Have to keep resetting quota for user on CentOS 6.5 while using VirtualMin

I have VirtualMin installed on a development server running CentOS 6.5. None of the users have explicit quotas, yet periodically I get write issues when running as that user. If I run as root, I have ...
2
votes
0answers
52 views

Can I rely on scsi host numbers to always stay the same?

I want to detect whether a disk is attached to the correct sata-port. While lsscsi gives me some useful information about the used host, I was wondering whether the SCSI host number will always stay ...
2
votes
0answers
36 views

actual disk iops and write merging

/dev/sdb has LVM and exposes a single logical volume, dm-0. While writing to dm-0, /proc/diskstats reports: # of writes completed sdb 29646717 dm-0 131315099 # of writes merged: sdb 101668283 dm-0 ...
0
votes
1answer
78 views

Linux - KVM - very slow disk io

The I/O performance of my new server is pretty low. I Googled and tried everything I can imagine. First of all, here are the Hardware Components: AMD Opteron(tm) Processor 6344 4x Seagate ...
3
votes
1answer
48 views

Why are cgroups (blkio serviced bytes) and iotop producing diverging results

I work with lxc user space tools on ubuntu 14.04 and I want to perform some stress tests and benchmarking within a container. I know that free and htop are not working properly in a container. I am ...
1
vote
1answer
39 views

How to identify EBS volumes vs local volumes on running EC2 instance

On a running EC2 instance, how do I identify EBS volumes and local disks ? I would like to identify them from shell. fdisk, lsblk is not helping to pinpoint the EBS volumes only. Lets say I have ...
0
votes
1answer
48 views

How to correctly move application data to an attached disk on an Azure Linux VM

I have a Linux VM on Azure that originally came with a 30G OS disk. As I had an application that had accumulated a lot of data, I attached a new disk through the Azure Dashboard and here is how it ...
0
votes
1answer
135 views

Abnormal CPU usage during Disk Write Operations

I have a decent CentOS 6.5 dedicated host (CentOS 6.5/E3-1230 3.2Ghz Quad Core + HT/16GB/Software Raid 1 SATA II/WD2503ABYX/ext4) with the default CentOS kernel and "elevator=deadline" in grub. I/O ...
2
votes
1answer
91 views

mdadm constant disk i/o

I have an mdadm array which has constant disk i/o. I know it's the array bc my server shows which specific drives have activity. According to iotop there's a constant disk write of 3-6 Mbps, however, ...
0
votes
1answer
56 views

Why is file rewrite slower?

on Linux, using various benchmark tools (bonnie++, iozone, etc) on ext4 (but i guess it's the same on other FS), rewrite is always slower than write to new files. For example, using bonnie++, with ...
1
vote
3answers
94 views

Moving partitions to the root partition

I am currently stuck with a restrictive partitioning scheme that makes my partitions fill up. It looks like this: /dev/sda7 870G 315G 511G 39% / /dev/sda6 2.0G 271M 1.6G ...
5
votes
2answers
1k views

Relation between disk IOPS and sar tps

I'm trying to estimate IOPS requirements of my application running on 32-bit CentOS 6.2. I started to take some measurement on a machine with SATA disks and I'm quite confused of difference between ...
0
votes
0answers
97 views

Linux not buffering block I/O when the device is not “in use” (i.e. mounted)

I am installing new server and I've found an interesting issue. The server is running Fedora 19 (3.11.7-200.fc19.x86_64 kernel) and is supposed to host a few KVM/Qemu virtual servers (mail server, ...
6
votes
3answers
342 views

How to keep subtree removal (`rm -rf`) from starving other processes for Disk I/O?

We have a very large (multi-GB) Nginx cache directory for a busy site, which we occasionally need to clear all at once. I've solved this in the past by moving the cache folder to a new path, making a ...
0
votes
1answer
106 views

Maximixing performance for disk usage queries in linux using du -s or df while maintaining accuracy?

I'm running a script to find out the disk usage on a wide range range of VPS (size ranging from less than 1 GB of usage to over 200 GB of usage)... I'm trying to maintain performance (EG: no extra ...
0
votes
0answers
35 views

How to rearange disks with a new SSD

Here is the problem: I have a Debian server with only 4 disk bays. At the moment there are 4 x 1GB SATA disks in software RAID 10. I'd like to swap one of the SATAs with a 1GB SSD disk and move the OS ...
2
votes
0answers
155 views

Convert single O/S disk to RAID 1 - Ubuntu 12.04 LTS

I have a server running Ubuntu 12.04 LTS with only a single drive. There are 2 more empty hot swap bays in the chassis. I want to add a little redundancy by adding a RAID 1 to the system. The ...
1
vote
1answer
4k views

Is it possible to on-line shrink a EXT4 volume with LVM?

Today I tried this on my machine with OpenSUSE 12.3 (kernel 3.7): # resize2fs /dev/mapper/system-srv 2G resize2fs 1.42.6 (21-Sep-2012) Filesystem at /dev/mapper/system-srv is mounted on /srv; on-line ...
3
votes
1answer
395 views

iotop and iostat disagree

I'm trying to understand what's going on with my server's disks. It's running Ubuntu 12.04LTS and I'm used to using iostat to know when the disk is the bottleneck. But iostat -xd looks to me like ...
0
votes
1answer
36 views

RAID1 Disk blocks don't match but no errors

So I have couple of disks configured with RAID1. The device is: md2 : active raid1 sda5[0] sdb3[1] 274324348 blocks super 1.1 [2/2] [UU] bitmap: 1/1 pages [64KB], 65536KB chunk Though when I ...
1
vote
1answer
138 views

Which directory hierarchy will be the best/fastest?

I have a pretty big directory with many cache files which I want to reorganise for max performance (access times). 2x 2TB SATA III drives, software RAID 1 (mirroring) OS: Ubuntu 12.04 LTS ...
1
vote
0answers
53 views

Rebalance pooled disks

Using mhddfs multiple drives were pooled to form a big virtual mountpoint. Now using the mlimit option unbalancing is prevented, but the drives are already in an unbalanced state. Is there a script ...
1
vote
1answer
98 views

Recover data after lvreduce on “/”

I accidentally ran lvreduce on / instead of "/home" on a RHEL 5.9 system that unfortunately had a lot of code that was not backed up, and the system will not boot now obviously. What is the best way ...
4
votes
3answers
1k views

PostgreSQL slow commit performance

We are having some problems with a PostgreSQL configuration. After some benchmarks I found out that very simple queries are taking a relatively long time, upon furter inspection it appears that the ...
12
votes
2answers
470 views

df vs du. Is my disk really full?

Strange problem... Why i have full / partition used, but it's not really used? Fast info: xwing ~ # df -h Filesystem Size Used Avail Use% Mounted on rootfs 16G 15G 75M 100% / ...
9
votes
1answer
2k views

Why is this SSD drive failing with bad sectors, and was it predictable?

Note: this question was previously closed as off-topic. You can read the discussion. My reasons for asking it here are: This drive is in an offline content cache server for schools in rural Zambia. ...
0
votes
3answers
1k views

Re-sizing disk partition linux/vm

I VM Player running a linux guest and I was wanting to know how do I expand the disk? In the VM player I gave more disk space but I am not sure how to mount/expand/connect the new disk space to the ...
0
votes
2answers
733 views

Output of /proc/diskstats in ubuntu

can anybody tell me about 11th field in /proc/diskstats? The documentation says that it is weighted # of milliseconds spent doing I/Os. Is it like # of milliseconds spent for DiskIO in a second? I ...
2
votes
1answer
51 views

How to dump data written to disk

Question : How to dump data (byte-stream) written from an application to the filesystem ? (something like tcpdump but for IO/file). Ideally it should be able to "attach" and dump the stream while it ...
3
votes
1answer
1k views

Find current IOPS usage of EBS volume from my application on AWS EC2

I am relatively new to AWS and disk performance. I am trying to figure out how much provisioned IOPS does my application need to perform well. Currently My PHP and MySQL application is hosted on EC2 ...
1
vote
2answers
914 views

Why do I get “No space left on device” when running mail

First of all I've checked these two solutions on serverfault but I'm still having issues. Here's my problem: root@myserver:/# mail /tmp: No space left on device Firstly I checked the filesystem ...
2
votes
3answers
167 views

How do I determine the number of seeks performed on Linux?

I have two programs that write to my servers disk. One I wrote, it does linear writes, it's writing data quickly. Another I'm benchmarking, it's writing data at a 3rd of the speed. It doesn't do much ...
1
vote
1answer
383 views

IOPS write increased, Disk write latency decreased, Avg req size decreased - Page load speed decreased

I have noticed decrease in server performance (page load speed become lower), then I went to investigate and have found in munin graphs (which tracks server's resources) that there was big changes on ...
2
votes
3answers
470 views

Disk write speed much slower than read speed

I have a VPS server (WiredTree), running CentOS. After experiencing some performance issues I created a simple benchmark for disk read/write speed using the following script: echo Write to disk dd ...
0
votes
2answers
248 views

SSD suddenly full

Today the hard drive of our server was suddenly full. The disk usage always stayed around 50 % in the weeks and months before (old data is regularly expunged from the server). I deleted 10 GB of ...
2
votes
2answers
102 views

Is it reasonable that a random disk seek & read costs ~16ms?

I am frustrated about the latency of random reading from a non-ssd disk. Based on results from following test program, it speeds ~16 ms for a random read of just 512 bytes without help of os cache. I ...
0
votes
1answer
44 views

Does soft link affects xml parsing and database process

I have a php code that does an xml parsing and inserts data into the mysql database. The code can process one xml file in an average of 18 minutes. Since I will be having lots of xml files and ...
-1
votes
3answers
146 views

Ubuntu webserver is out of space

Apparently, I was using xvda1 disk which is out of space. How do I change the /etc/fstab so that I can make my xvda2 for top level, and xvda1 as additional resource? It's an EC2 instance: root@~# ...
2
votes
1answer
353 views

Mount a partition to two mount points

I have a partition called sda4. And I want to store the mysql data and xml files on that partition because the partition which mysql and domain are installed has little space. So I'm planning to ...
0
votes
1answer
1k views

resize root partition without using live cd and lvm [duplicate]

Possible Duplicate: Do partitions needed to be unmounted when resizing a partition? I want to know if it is possible to resize an existing root partition without using live cd. The server ...
0
votes
1answer
134 views

Disk speed test linux

Is there any simple command (or tool) to test the speed (MB/sec) of disk access? I've found hdparm but It look it only works for local disk. I need to evaluate the speed of remote NFS-mounted disk. ...
11
votes
4answers
2k views

Available disk space on Unix/Linux OS

How to get available disk space on Unix/Linux OS, including unallocated space (which wasn't assigned to any partitions)?
2
votes
2answers
140 views

Do we need to perform disk checking periodically on Linux

Do we need to perform periodic disk checking,for bad blocks and bad sectors?. Our servers havent been restarted for last 4 months,also no disk checking have been performed on any disks. Can that can ...
1
vote
2answers
870 views

How iostat figures out to take CPU idle time to consider as %idle or %iowait?

I was going through iostat man page. According to it, %iowait Show the percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request. %idle ...
1
vote
2answers
365 views

Refresh /dev/sdx list

I've been messing around with my storage array (in that case 2xMD3000 SAS) and between the scans/rescans/delete/add my /dev/sdx block devices are all messed up. Some of them are non existent and using ...
1
vote
1answer
438 views

Controlling mdadm faulty disk rebuild order in RAID 10 array

I have a Linux mdadm RAID 10 array comprising of 6 (SATA) disks configured with n2 copies. While pulling out one disk, another one in another mirror pair failed. Leaving me with: $ cat /proc/mdstat ...
1
vote
2answers
123 views

Disk space profiling in Unix

I'm looking for a tool to summarize how disk space is being used on very large partitions. Our file system is around 950TB, mostly broken up into 20TB partitions. There are some really nice graphical ...
3
votes
0answers
43 views

How can I measure disk cache churn on Linux? [duplicate]

Possible Duplicate: Is there a way to get Cache Hit/Miss ratios for block devices in Linux? I have a file server which serves out large (25GB-1TB+) files over the network from local ...
1
vote
1answer
135 views

Linux RAID: Replacing Failed Drive…permanantly

Okay, odd question here. I have a server with RAID 5. A drive failed, in a really physically in a really odd way. On the machine it boots and is seen by the BIOS but...no partition can be seen on the ...
4
votes
1answer
237 views

Can I generate I/O activity with a max (throttled) throughput?

For example, is there a tool or method where I can say (for example) "generate up to 50 MB/s of read activity to this file, but no greater"? Or configure a tiny delay between read operations, which ...