0
votes
2answers
60 views

Unreasonable performance expectations for RAID 0 performance?

This is my first time building a machine with a hardware RAID card. We bought a Dell T620 with the H710P RAID controller (1GB NV Cache), a 160GB Solid State Drive (SATA Read Intensive MLC 3Gbps), and ...
12
votes
7answers
580 views

How do storage IOPS change in response to disk capacity?

All other things being equal, how would a storage array's IOPS performance change if one used larger disks. For example, take an array with 10 X 100GB disks. Measure IOPS for sequential 256kb block ...
2
votes
0answers
37 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
61 views

Install Winsat on server 2012? Windows System Assesment Tool

I use winsat disk to see my disk read / write speed windows 8 and it works great: cmd : winsat disk -drive c Can this be used on windows server 2012?
1
vote
1answer
126 views

upgrade/reinstall vmware vsan from beta

Being a VSAN beta tester I decided to upgrade to GA version as VMWare suggests for production sites. They say, it is not possible/supported to upgrade from beta to GA version, and I did not upgrade, ...
0
votes
0answers
34 views

How do I check disk performance of LVM drive?

I have a CentOS server with 2 hard drives configured to use LVM over RAID1. How do I benchmark my hard drive? As seen in this question, I have used the following commands: # check read performance ...
0
votes
1answer
138 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 ...
0
votes
0answers
64 views

Debian mail server's Maildir folder with too many files causing disk I/O to go on high load

I have a Debian mail server running Postfix, Courier and Maildir, with disks on EXT3 filesystem. I have noticed that when I use my webmail application (Squirrelmail, in this case). It gets some kind ...
1
vote
2answers
187 views

Why does dd show slow disk speed first time?

I'm checking the disk speed of a hdd on CentOS 6 using dd command. The setup is a DRBD setup - with this server being primary. To ensure that I get correct values, I execute the dd command 3 times ...
4
votes
2answers
321 views

Importance of disk alignment for Windows Server 2012

I saw article about Disk alignment here and also here.Also there where some references that windows server 2003 has some problem with disk alignment. After reading article I am confused whether we ...
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 ...
1
vote
2answers
45 views

How to limit disk performance?

I am load-testing a web application and studying the impact of some config tweaks (related to disk i/o) on the overall app performance, i.e. the amount of users that can be handled simultaneously. ...
1
vote
1answer
757 views

Slow Write Speed on ESXi host

I have an ESXi 5.0 free host with an internal datastore of 7.2K 5 disk RAID 5 using a PERC 710 mini RAID controller in a Dell Poweredge R620 Server with 32GB Ram and a 12 Core Xeon. I seem to get ...
3
votes
1answer
5k views

what is acceptable datastore latency on VMware ESXi host?

Looking at our performance figures on our existing VMware ESXi 4.1 host at the Datastore/Real-time performance data Write Latency Avg 14 ms Max 41 ms Read Latency Avg 4.5 ms Max 12 ms People ...
4
votes
4answers
747 views

Disk performance below expectations

this is a follow-up to a previous question that I asked (Two servers with inconsistent disk speed). I have a PowerEdge R510 server with a PERC H700 integrated RAID controller (call this Server B) ...
0
votes
1answer
1k views

Upgrading a PERC h310 to a PERC H710 mini RAID controller on a Dell R620

I have an ESXi 5.0 Free license host using an internal Datastore (RAID 5, 5 Disk) that was configured with a Dell PERC h310 RAID controller. The disk performance was very poor, so I upgraded to the ...
2
votes
1answer
73 views

Understanding %DiskTime in Perfmon

I have a server that's been jumping around 100-700 %DiskTime for the past few days. I understand this indicates an I/O bottleneck -- but what do I do from here? What do I need to check or change in ...
0
votes
2answers
162 views

Disk Cached IO very slow

I have two boxes with exactly same hardware configuration. Both having RAID0 (created using mdadm) over SATA disks. But I am getting different cached reads while testing using hdparm command. $ ...
0
votes
0answers
67 views

Two servers with inconsistent disk speed

I have two servers of identical spec (bought at the same time), except for the drive configuration: Server A: C: and D: drives are partitions on the same 2 disk RAID 1 E: is a 2 disk RAID 0 ...
1
vote
1answer
957 views

KVM + NFS poor disk performance

Situation: We have an Ubuntu server that hosts three VMs using KVM. All guests as well as the host need to access the same files in a certain subfolder of /var . Thus, the subfolder is exported via ...
1
vote
3answers
459 views

IBM SR-BR10i RAID Controller too slow with VMware ESXi

I'm transferring a virtual machine from one ESXi host to another using SSH on both ESXi Servers. But it's painful slow, it's a massive 750GB .vmdk disk image, the VM is stopped (with downtime) and ...
3
votes
1answer
398 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 ...
2
votes
1answer
53 views

Why the I/O rate difference between an LV and PV?

I have been doing some benchmarks reading with dd from both the LVM device and the PV device and I got some unexpected results: $ sync ; echo 3 > /proc/sys/vm/drop_caches; dd bs=1M count=1024 ...
0
votes
3answers
231 views

Dramatic disk I/O performance difference for two disks on same machine

A small machine (1 core, 1 GB RAM, CentOs 6.3) virtualized via Citrix Xen has 3 virtual disks with very different sizes. > cat /etc/fstab (snippet) ... /dev/mapper/vg_stagingnfs-lv_root / ext4 ...
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
2answers
6k views

How to get more I/O performance from Citrix XenServer?

I have a Citrix XenServer 6.1 installed on a HP Server (1x Intel Xeon E5630 @ 2.53GHz (4 cores, 8 threads, RAM: 752MB for dom0 and 55286MB for the guests). The server has 2 scsi mirrored disks and is ...
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 ...
0
votes
1answer
43 views

Should getfacl be running constantly and is it normal for it to be using greater than 90% of available disk I/O?

I've recently been getting alerts from our server monitoring software about greater than 90% disk I/O utilisation. I installed iotop and there are three instances of the following process showing up ...
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
1answer
302 views

MySQL Extremely High Disk Activity (Read Operations)

I have 1GB Linode VPS with a standard LAMP stack. Apache is tuned fine but for some reason MySQL's disk usage is high. This is causing really slow site load times. RAM and CPU usage are fine. Can ...
1
vote
1answer
386 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
473 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 ...
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 ...
-3
votes
1answer
48 views

number of disks for RAID config vs. effect on performance? [closed]

I was wondering how the number of disks used for RAID configuration affects performance? I know that it takes longer to rebuild data, but are there any other performance areas affected??
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
3answers
1k views

RAID10 without write-back cache = horrible write performance?

I have just provisioned a dedicated server on singlehop. I'm running it through some tests to know what to expect performance-wise. On the I/O side (with 4 1TB disks in RAID 10) I get: write-cache ...
1
vote
2answers
871 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 ...
4
votes
1answer
238 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 ...
1
vote
1answer
400 views

How do I measure and compare disk performance of my Hyper-V Windows VM?

I'm not sure whether this sounds stupid or lazy, but I'm really not sure. I have a problem with the performance of a VM setup (2008R2-64bit Hyper-V running a 2003R2-32bit Windows server) and I'd like ...
9
votes
3answers
534 views

Slow filesystem access

I'm trying to diagnose a slow filesystem issue on a server I look after. It's been ongoing for quite some time, and I've run out of ideas as to what I can try. Here's the thick of it. The server ...
0
votes
2answers
610 views

How to analyse performance ESXi NFS Copy between datastores

I'm having trouble with ESXi backup/restore performance. My setup: VMWare ESXi 5.0.0 on a HP ProLiant DL 360 G6, runnnig RAID 5 on a P410 SmartArray as SAS QNAP Nas (QNAP TS-809U-RP NAS 8 bays ...
1
vote
1answer
196 views

optimizing ext[234] for small file throughput

I have a system that has a high throughput of small files on disk, i.e. a huge number of small files are created, written and deleted within seconds. Are there any reasonable ext2/ext3/ext4 mount ...
7
votes
2answers
291 views

Disk latency is growing since a few days ago, with no special change in disk throughput

Here is the disk latency graph of my server. The server has two 5400 RPM 32MB Cache SATA 3.0Gb/s hard drives mounted with software RAID 1 configuration. No special changes has happend in those days ...
6
votes
1answer
122 views

How to prevent IO Load under Linux for Video serving?

I'm currently serving videos of conferences via Nginx on 3 servers; 4 cores, enough memory (no swap used) and RAID-10 with 8 drives per server. Unfortunately iostat -xd 1 gives me 100% on all 3 ...
3
votes
1answer
159 views

Is WinSAT reliable to test the speed of my iSCSI, Fibre SAN, under bare metal or Virtualized?

I discovered the following command in this whitepaper: WinSat disk -read -ran -ransize 4096 -drive c Is it reliable to use against a SAN, or iSCSI drive? I would like to compare the output of ...
3
votes
4answers
1k views

What does “random seek time” really means in HDD benchmarks?

I am currently benchmarking a hard drive. I am using HW32 for the measurement. The result has two parts: random seek time: 20 ms random read throughput: 30 Mbytes/s I am not sure the methods HW32 ...
0
votes
1answer
495 views

Short write and read speed disk benchmarking

We're using cloud hosting for some of our backend servers and we noticed that performance on the disks (which as confirmed by the provider are shared with other customers) vary depending on the ...
5
votes
5answers
650 views

Linux: how many disk I/O does it take to read a file? How to minimize it?

According to this paper on Facebook's Haystack: "Because of how the NAS appliances manage directory metadata, placing thousands of files in a directory was extremely inefficient as the ...
0
votes
1answer
698 views

Xen Disk Performence Issues

I'm currently using Xen PV on CentOS 5 with my domU's as flat files running on a hardware RAID controlled (write cache enabled) formatted with XFS. On the dom0 I can get about 500MB/s in a 2GB dd ...
3
votes
1answer
536 views

Poor NFS performance when sequentially reading large files

I have an NFS3 server with multiple clients. Each client is sequentially reading a different large file, and performance is very poor. Here is what I am observing in iostat on the server for the disk ...