Questions about disk drives under the UNIX and Linux systems. See also the "filesystems" tag.

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7
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1answer
134 views

Command to generate /dev/disk/-by-path/ name on a system without udev daemon

On most Linux systems udev usually creates symlinks in /dev/disk/by-uuid/ /dev/disk/by-path/ which point to actual device nodes (/dev/sda, /dev/sdb, etc). I don't have udev on my system, and I ...
3
votes
1answer
48 views

Why is the block size of a partition smaller than that of the underlying disk?

My understanding is that the block (in the phrase "block size") is like an IO buffer, or minimum IO size for a device. Since partitions are built on top of physical devices, how can they have blocks ...
2
votes
1answer
41 views

How can I differentiate disk I/O occured explicitly by a user and OS prefetching?

I am monitoring disk I/O usages of an application program (running on CentOS 7) It uses lots of sequential disk I/Os where I expect that OS prefetching is something! dstat shows how many disk I/Os ...
3
votes
0answers
15 views

“leaky bucket” style disk io throttling using linux kernel

My goal is to prevent one kvm guest's disk i/o usage from negatively affecting other kvm guests on the same host. The host has one disk array - and separating guests onto different physical disks is ...
3
votes
0answers
49 views

Use a “Friendly” Label on Drives or Partitions in FreeBSD

Maybe I am missing this and it's really simple, but I cannot figure out how to label a BSD disk. I have looked at tunefs or gpart and even disklabel, however none do what I am looking for - I don't ...
3
votes
0answers
893 views

Unable to close a Luks partition

For backup purposes, I have "snapshotted" a LVM partition. This partition was crypted so I have opened this Luks partition (snapshot) in order to do my backup. The problem is that I have forgotten to ...
3
votes
0answers
300 views

Setup Cloudmin on Centos installed in LVM

I installed CentOS 6 with default LVM partition pattern. according to this pattern Can I use Cloudmin and store KVM Disks in LVM as Logical Volume? I think Cloudmin requires creating new logical ...
2
votes
0answers
20 views

How to shrink sda disk with XFS filesystem

We have a RHEL 7 server with 2 disks (sda and sdb). Our /, /var/log and swap are on sda, /var is on sdb. We use LVM and XFS. sda is too big (160 GB) and we would like to shrink it to 40 GB. We can ...
2
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0answers
41 views

unix c-shell : disk checking

im totally new in shell scripting. I have task to simplify an old c shell script. Basically, the script have 10 devices that using hp-ux and i want to check the disk space in each devices. my ...
2
votes
0answers
34 views

GNOME Disks Sample Size

I'm trying to use GNOME Disks to test my disk performance and, according to my previous experience, I'd like to set the sample size to 8K, 16K and 32K. However, I see the minimal sample size in its ...
2
votes
0answers
110 views

LVM partition not mounting

There was a drive failure on a disk in a RAID1 configuration. I removed the bad disk and reconfigured the RAID1 to only use the good disk. When I reboot the machine there are missing LVM partitions. ...
2
votes
0answers
314 views

Disk I/O latency using /proc/vmstat file

How do I calculate disk read and write latency in Linux? Is it possible to do the calculation using /proc file system? I am using iostat and vmstat command. But I do not understand how the ...
2
votes
0answers
137 views

View syscalls/kernel activity for I/O from a running process

I'd like to be able to view syscalls or kernel activity for a process...I'm not actually sure of the terminology I need here! Specifically I'm looking for the difference between I/O going to local ...
2
votes
0answers
689 views

How do I get ata-style IDs in /dev/disk/by-id to work for USB disks?

I have USB drive dock that I'm plugging SATA drives into. The way they show up in /dev/disk/by-id seems to be dependent on whether the drive has a partition table (usb if not, ata if yes). This makes ...
2
votes
0answers
135 views

SMART extended offline test validity

Is it possible for the smartctl -t long /dev/sda to complete without error and still the drive fail? How detrimental to the disk's life expectancy is running the test daily/weekly? Thanks!
2
votes
0answers
272 views

expanding boot, moving LUKS root

GPT > Partition2 > LUKS > btrfs I need some additional space for my boot volume, so far I did: Shrink my btrfs volume by 250MB. btrfs resize -250M / Shrink the LUKS root volume cryptsetup ...
2
votes
0answers
516 views

The proper way to turn off an external sata encolsure?

I have an e-sata external enclosure with a port expander and 4 sata disks in it that I use for periodic backups. I have what I think is a sound method for powering it off, but not sure if it is the ...
2
votes
0answers
216 views

Block Devices & Partitions

I partitioned a microSD card (mmcblk1) into two partitions mmcblk1p1 and mmcblk1p2. If use a dedicated card reader I am able to see the entire SD card and its partitions using various disk management ...
1
vote
0answers
16 views

iozone read test slower than fio

I'm currently using both iozone and fio to test my disk performance. However, iozone show much much poor speed than what is shown from fio. (about 1/3) Now the question for me is which number should ...
1
vote
0answers
13 views

Extending XFS filesystem CentOS 7 Google Cloud

I have Googled everything, and literally nothing is working. Here is df -h: Filesystem Size Used Avail Use% Mounted on /dev/sda1 10G 7.7G 2.4G 77% / devtmpfs 103G 0 103G ...
1
vote
0answers
25 views

Reclaiming disk space in Ubuntu

In VMWare the hard disks took 13.6 GB, But with df, only 5.8 GB is occupied I don't quite get it. This Virtual Machine has no snapshots, and I already clicked on refresh button in VMWare Fusion ...
1
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0answers
30 views

monitoring block access to disk

I am looking for a way to monitor access to disk blocks, and to monitor the access as a bitmap of blocks. I also need the capability to freeze (and queue) the device block access (and also to ...
1
vote
0answers
29 views

iostat ( column svctm is not trusted any more ) what to use instead?

I'm running a Linux Server with "Oracle Linux Server release 6.5" which is pretty much the same as RedHat Version. I need to determine the latency on my disk devices. The man page of the iostat ...
1
vote
0answers
62 views

sysv and unknown partition table?

We have disk about 1985, It has a Unix.But we didn't know type of Unix.I did the following step : dd if=/dev/sdc of./all_of_disk.iso #sdc is the given disk Then : hexdump -C all_of_disk.iso > ...
1
vote
0answers
76 views

List partition type GUID's for all disks from command line?

I need to list the partition type GUID's from the command line. Note: This is not the same as the partition UUID. Basically I'm needing to search for all disks that have the Ceph OSD type GUID: ...
1
vote
0answers
154 views

Disk configuration options, what can affect performance

I have 2 disks, the same model and vendor, first one , probably performs faster. We do write into multiple files. Can you compare 2 configurations and tell what can affect performance? 1. (faster) *-...
1
vote
0answers
192 views

How can I get read/write instant speed of a Hard Drive using /proc/diskstats data?

I know that the proc/diskstats file presents these data columns: 1 - major number 2 - minor mumber 3 - device name 4 - reads completed successfully 5 - reads merged 6 - sectors read 7 - time spent ...
1
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0answers
171 views

Flash memory and set to read only , Is it virus?

Becuase some of limitation of MS.Windows, my friends and my family gime their flash memory to solve their problem. Such as format, partitioning in Linux with the cfidsk ,parted, sfidsk(dump and ...
1
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0answers
179 views

Separating SAS from SATA drives

I have to list all SAS drives and separately list all SATA drives, I'm working on CentOS6 and tried lots of commands which will give some specific information about bus of disks. Let me show you ...
1
vote
0answers
76 views

Shared NTFS partition conflict, files written under Debian gone

I have a dual-boot W7-Debian Jessie on my laptop, and a NTFS partition initially left for sharing data between OS and keeping big files. With myself getting used to Linux, rebooting to windows became ...
1
vote
0answers
38 views

Disk copying with two OS on it

I want to change HDD in my laptop to bigger one. I have installed WIN XP and Mageia Linux and GRUB ver 1 as bootloader. So I want to use such procedure for copying and changing disk: plug new one ...
1
vote
0answers
472 views

Monitoring Disk Latency

We have quite a few physical machines in our environment, yet we have no trending data over a period of time for disk latency statistics. We can easily run the standard iostat commands to see what the ...
1
vote
0answers
243 views

midnight commander: rules for accessing archives through VFS

Midnight Commander uses virtual filesystem (VFS) for displying files, such as contents of a .tar.gz archive, or of .iso image. This is configured in mc.ext with rules such as this one (Open is Enter, ...
1
vote
0answers
70 views

Edit partition of disk part of a ZFS Raid

I've gota strange problem. Since a previous failure from one of my hard drive, I had to replace one of my 4 hdd running in RAIDZ. But since I changed this disk, the last partition of my disk appear ...
1
vote
0answers
23 views

Install system to Disk on Chip

I'm looking for an easy way to install linux on a PC104 (x86 no cmov) system with a Disk-on-Chip. It can be a very simple system (BusyBox, etc) or a distro the installs in under 512mb. I just need to ...
1
vote
0answers
299 views

How different is I/O handling of hard disk in AIX and Redhat Linux?

I am running a hadoop I/O workload in redhat linux and have ran that in IBM AIX as well with same underlying hardware, disk and disk configuration. With the default settings on the os redhat linux is ...
1
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0answers
2k views

How to set up ZFS with ZIL and L2ARC SSD?

I have been considering bcache and flashcache. However my friend suggested me something called ZFS. In fact it says that formating disk with ZFS can actually do the exact same thing without kernel ...
0
votes
0answers
22 views

Ubuntu trusty format disk slower than RHEL7?

I observed that disk formatting is much slower in Ubuntu than in RHEL7. Does anybody know why that is? EDIT: Forgot to mention, I'm formatting the disk with ext4. Using mke2fs
0
votes
0answers
28 views

sfdisk does not create block files for corresponding partition

I have partitioned my disk using sfdisk. And the (7)partitions got created successfully. sfdisk -l also lists all the (7) partitions which I configured. But the strange thing is, the corresponding ...
0
votes
0answers
37 views

Random write on DISK benchmark shows high read rate on iostat

I am running a random write benchmark directly on some disks (HDD & SDD) and I am getting some weird output data on the iostat monitor. Besides the usual write rate, there is a read rate that I ...
0
votes
0answers
14 views

How do I increase a partition size of a virtual disk?

I created a file using dd if=/dev/zero of=virt_disk bs=1024M count=50. I then formatted this is a vfat file system. Now I want to extend this. I added 5 more MiB of space as dd if=/dev/zero bs=1024M ...
0
votes
0answers
56 views

linux + resize2fs with Operation not permitted error

I am trying to increase the /opt to 65g but I get the following message Operation not permitted While trying to add group #8256 what is the resolution for that? root@linux:/opt # lvresize -L 65g /...
0
votes
0answers
16 views

why does SCSI Host value change during reboot?

I have attached a virtual disk to my VM and the Host value changes during reboot. How can we bind it to a particular value? Host: scsi2 Channel: 00 Id: 00 Lun: 00 or Host: scsi3 Channel: 00 Id: 00 ...
0
votes
0answers
119 views

how can I see the uuid of a disk in my system WHEN IS NOT LISTED IN /dev/disk/by-uuid

I have a problem in my system, that I don't understand: there are no disks UUIDs, only partitions UUIDs: ls -al /dev/disk/by-uuid/ total 0 drwxrwxrwx 2 root root 140 Nov 21 20:36 ./ drwxrwxrwx 5 root ...
0
votes
0answers
26 views

SSD as write target during reads

I have a real-time application which always writes data to a RAID 10 HDD configuration in a sequential manner at around ~50 MB/s. It uses mmap and writing should never be blocked due to waiting I/O. ...
0
votes
0answers
49 views

How do I interpret GNOME Disks' benchmark results?

Having ordered a new USB drive for my parents, I decided to use the Benchmark option in GNOME Disks. The results were interesting: A third run with a sample size (odd phrasing!) of 100 MB gave ...
0
votes
0answers
58 views

CloneZilla, does exist a simpler method?

While browsing the web for backing up my disk, I often see CloneZilla in the results. As a beginner with Linux, the process seems tricky to me (Live USB, etc). Note: I plan to back up my whole disk (...
0
votes
0answers
113 views

Any tool or command can detect flash disk or SSD memory type?

Here I mean "SLC" or "MLC", basically, how many bits per cell for the NAND memory. Is there anything we can get? Thanks.
0
votes
0answers
42 views

Why does reading from a symlink to network location cause local disk activity?

I am running RHEL 6.4 and have a symbolic link in my home directory to a large file stored elsewhere on a network. My home directory is a network location as well. I've noticed that when I run a ...
0
votes
0answers
153 views

AIX equivalent of Solaris' iostat -E

On Solaris you can use the command iostat -En to view "disk error statistics" as counted by the kernel since the last reboot, where the -n option causes iostat to show "nice" device names. I'm ...