Hot resize Multipath Disk – Linux
This post is for the users of the great dm-multipath system in Linux, who encounter a major availability problem when attempting a resize of mpath devices (and their partitions), and find themselves scheduling a reboot.
This documented is based on a document created by IBM called "Hot Resize Multipath Storage Volume on Linux with SVC", and its contents are good for any other storage. However - it does not cover the procedure required in case of a partition on the mpath device (for example - mpath1p1 device).
I will demonstrate with only two paths, but, with understanding this process, it can be well used for any amount of paths for a device.
I do not explain how to reduce a LUN size, but the apt viewer will be able to generate a method out of this document. I, for myself, try to avoid as much as I can from shrinking LUNs. I prefer backup, LUN recreation, and then restore. In many case - it's just faster.
So - back to our topic - first - increase the size of your LUN on the storage.
Now, you need to collect the paths used for your mpath device. Check this example:
mpath1 (360a980005033644b424a6276516c4251) dm-2 NETAPP,LUN
[size=200G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=4][active]
\_ 2:0:0:0 sdc 8:32 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 1:0:0:0 sdb 8:16 [active][ready]
The devices marked in bold are the ones we will need to change. Lets get their current size:
blockdev --getsz /dev/sdb
419430400
Keep this number somewhere safe. We can (and should!) assume that sdc
has the same values, otherwise, this is not the same exact path.
Collect this info for the partition as well. It will be smaller by a tiny bit:
blockdev --getsz /dev/sdb1
419424892
Keep this number as well.
Now we need to reread the current (storage-based) size parameters of the devices. We will run
blockdev --rereadpt /dev/sdb
blockdev --rereadpt /dev/sdc
Now, our size will be slightly different:
blockdev --getsz /dev/sdb
734003200
Of course, the partition size will not change. We will deal with it
later. Keep the updated values as well. Of course, the multipath still
holds the disks with their original size values, so running 'multipath
-ll' will not reveal any size change. Not yet.
We now need to create editable dmsetup map. Use the current command to create two files: cur and org containing this map:
dmsetup table mpath1 | tee org cur
0 419424892 multipath 1 queue_if_no_path 0 2 1 round-robin 0 1 1 8:32 128 round-robin 0 1 1 8:16 128
Important part - explaining some of these values. The map shows the
device's size in blocks - 419424892. It shows some parameters, it shows
path groups info (0 2 1), and both sub devices - sdc being 8:32 and sdb
being 8:16. Try it with 'ls -la /dev/sdb' to see the minor and major. At
this point, if you are not familiar with majors and minors, I would
recommend you do some reading about it. Not mandatory, but will make
your life here safer.
We need to delete one of the paths, so we can refresh it. I have decided to remove sdb first:
multipathd -k"del path sdb"
Now, running the multipath command, we will get:
mpath1 (360a980005033644b424a6276516c4251) dm-2 NETAPP,LUN
[size=200G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=4][active]
\_ 2:0:0:0 sdc 8:32 [active][ready]
Only one path. Good. We will need to edit the 'cur' file created earlier to reflect the new settings we are to introduce:
0 419424892 multipath 1 queue_if_no_path 0 1 1 round-robin 0 1 1 8:32 128
The only group left was the one containing 'sdc' (8:32), and since
one group down, the bold number was changed from 2 to 1 (as there is
only a single path group now!)
We need to reload multipath with these settings:
dmsetup suspend mpath1; dmsetup reload mpath1 cur; dmsetup resume mpath1
The correct response for this line is 'ok'. We pause mpath1, reload
and then resume it. It is best to be in a single line, as this process
freezes IO for a short period of time on the device, and we prefer it to
be as short as possible.
Now, as /dev/sdb is not a part of the multipath managed devices, we
can modify it. I usually use 'fdisk' - deleting the old partition, and
recreating it in the new size, but you must make sure, if your device
requires LUN alignment, that you recreated the partition from the same
start point. I will dedicate a post some time to LUN alignment, but not
at this particular time. Just a hint - if you're not sure, run fdisk in expert mode and get a printout
of your partition table (fdisk /dev/sdb and then x and then p). If your
partition starts at 128 or 64, it is aligned. If not (usually for large
LUNs - at 63), you are not, and you should either be worried about it,
but not now, or should not care at all.
Back to our task.
We need to grab the size of the newly created partition, for later use. Write it down somewhere.
blockdev --getsz /dev/sdb1
733993657
Following the partition recreation, we need to introduce the device to the multipath daemon. We do this by:
multipathd -k"add path sdb"
followed by immediately removing the remaining device:
multipathd -k"del path sdc"
We need to have our 'cur' file updated, so we can release the device
to our uses. This time, we update both the size section with the new
size, and the new, remaining path. Now, the file looks like this:
0 734003200 multipath 1 queue_if_no_path 0 1 1 round-robin 0 1 1 8:16 128
As mentioned before - the large number in bold is the new size of the
block device. The amount of failure groups is one (1), also in bold,
and the device name is 'sdb' which is 8:16. Save this modified file, and
run:
dmsetup suspend mpath1; dmsetup reload mpath1 cur; dmsetup resume mpath1
Running the command 'multipath -ll' you will get the real size of the device.
mpath1 (360a980005033644b424a6276516c4251) dm-2 NETAPP,LUN
[size=350G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=1][active]
\_ 1:0:0:0 sdb 8:16 [active][ready]
We will need to reread the partition layout of /dev/sdc. The quickest way is by running:
partprobe
This should do it. We can now add it back in:
multipathd -k"add path sdc"
and then run
multipath
(which should result in all the available paths, and the correct size).
Our last task is to update the partition size. The partition,
normally, is called mpath1p1, so we need to read its parameters. Lets
keep it in a file:
dmsetup table mpath1p1 | tee partorg partcur
We should now edit the newly created file 'partcur' with the new size. You should not change anything else. Originally, it looked like this:
0 419424892 linear 253:2 128
and it was modified to look like this:
0 733993657 linear 253:2 128
Notice that the size (in bold) is the one obtained from /dev/sdb1 (!!!) and not /dev/sdb.
We need to reload the device. Again - attempt to do it in a single
line, or else you will freeze IO for a long time (which might cause
things to crush):
dmsetup suspend mpath1p1; dmsetup reload mpath1p1 partcur; dmsetup resume mpath1p1
Do not mistaked mpath1 with mpath1p1.
Our device is updated, our paths are online. We are happy. All left
to do is to online resize the file system. With ext3, this is done like
this:
resize2fs /dev/mapper/mpath1p1
The mount will increase in size online, and all left for us is to wait for it to complete, and then go home.
I hope this helps. It helped me.
dm-multipath and loss of all paths...
Create Huge disk partitions – Above 2TB...
HP-UX – allowed shells, and connecting FC Multipath to NetApp...
Aquiring and exporting external disk software RAID and LVM...
Related posts brought to you by Yet Another Related Posts Plugin.
Tags: dm-multipath, hot resize, Linux, lun, multipath, netapp, online resize, storage
This entry was posted
on Friday, August 19th, 2011 at 12:22 am and is filed under Disk Storage, Linux.
You can follow any responses to this entry through the RSS 2.0 feed.
You can leave a response, or trackback from your own site.
14 Responses to “Hot resize Multipath Disk – Linux”
- darkfader Says:
Now I’m really amazed. Most people will tel you this is impossible.
Mind if I refer to this in my next LVM training?Florian
- ez-aton Says:
You have my full support. This knowledge is meant to be shared.
I would be happy, though, to get a link to my site. Sometimes I write something intelligibleEz
- doron Says:
October 25th, 2011 at 10:11 pm
what about this procedure below?
http://zenhat.org/2011/04/02/how-to-extend-lun-without-reboot-redhat/ - ez-aton Says:
Quite similar, however, requires a umount/mount. My procedure does not.
Ez
- amir tal Says:
February 26th, 2012 at 6:16 pm
blockdev –rereadpt /dev/sde
BLKRRPART: Device or resource busy
- ez-aton Says:
February 29th, 2012 at 1:37 am
Too little info. Are you sure the device is available at that time?
- G Says:
No offense but you make this look like it is really hard. You can fix this way easier.
echo 1 > /sys/block/sdc/device/rescan (where sdc is replaced by
the device names for both paths, retrievable from multipath -ll)multipathd -k
At the prompt(path names dependent on what you got from multipath -ll):
del path sdc
add path sdc
del path sdd
add path sddNow look at fdisk -l
You should see the new size.
Remove the partition and recreate it with the same startpoint and the last block as endpoint.
partprobe
resize2fs /dev/mpath/…That should do the trick. The thing above is really dangerous to do.
Another option is using LVM and adding another partition in the new space instead of resizing the existing one.Hope this helps someone
- ez-aton Says:
I will be very glad to find out that you are correct. Simpler is better!
Next time I face resize issues, I will test your method.
CHeers!
Ez - Doron Says:
worked again for me – (even with 4 paths!!)
just a small issue – could you re-edit the “blockdev –getsz /dev/sdb”
into “blockdev –getsz /dev/sdb” so that cut&paste into linux will
work?10x again..
- ez-aton Says:
You don’t know how complicated it is to make WordPress not convert double minus symbol to a single dash. You own me one!
Ez - stef Says:
Good G !! but I have more easyer again :
scan for all device path
echo 1 > /sys/block/sdm/device/rescanand
multipath /dev/mpath/mpath1
multipathd -k’resize map mpath1′Let’s go to lvextend
- stef Says:
sorry I have forgotten the
pvresize /dev/dm-28
before
lvextend -L +1G /dev/vgname/lvname
resize2fs /dev/vgname/lvname - ez-aton Says:
Does it work with partitions?
Ez
- ez-aton Says:
I’m asking because I haven’t had the chance to try it just yet.
Ez
Hot resize Multipath Disk – Linux的更多相关文章
- VBoxManage.exe: error: Resize hard disk operation for this format is not implemented yet!
VirtualBox虚拟磁盘空间不够了,默认10G.想扩大,图形界面下没有找到可操作菜单.Google了一下用 Vbox自带的命令工具VBoxManage即可解决. C:\Program Files\ ...
- How To: set udev rule for setting the disk permission on ASM disks when using multipath on Linux 6.x
在RHEL6.4上安装11gR2的RAC时,使用了MULTIPATH来聚合绑定多路径的磁盘,并且修改磁盘的权限,赋予grid:asmadmin用户和组. 此时,在安装时可以发现磁盘,日志如下 INFO ...
- Azure上批量创建OS Disk大于30G的Linux VM
Azure上VM的OS盘的大小在创建时是固定的.Windows是127G,Linux是30G.如果需要批量创建的VM的OS Disk有更大的容量.可以考虑用下面的方法实现. 1 创建一台有Data-d ...
- multipath多路径实验01-构建iscsi模拟环境
multipath多路径实验01-构建iscsi模拟环境 前几天跟同事网上闲聊技术,吐槽之前自己没有配置过多路径的经历,虽然多路径的配置过程很简单,职责划分也应是主机或存储工程师来搞定,DBA只需要直 ...
- linux中LVM介绍及实验过程
LVM LVM这个词不仅一次出现过,在安装Centos时,磁盘分区时,默认分区就是使用LVM方式分区:再一个就是在OpenStack部署时候用到LVM作为后端存储.对LVM的理解还是不太清晰,查询资料 ...
- 如何在Linux上使用文件作为内存交换区(Swap Area)
交换区域(Swap Area)有什么作用? 交换分区是操作系统在内存不足(或内存较低)时的一种补充.通俗的说,如果说内存是汽油,内存条就相当于油箱,交换区域则相当于备用油箱. Ubuntu Linux ...
- pvresize - Unix, Linux Command
NAME pvresize - resize a disk or partition in use by LVM2 SYNOPSIS pvresize [-d|--debug] [-h|--help] ...
- Running ASP.NET Core applications on Windows Subsystem for Linux
Setting up Linux on Windows 10 First thing is to enable Windows Subsystem for Linux. It doesn’t inst ...
- Linux 驱动开发
linux驱动开发总结(一) 基础性总结 1, linux驱动一般分为3大类: * 字符设备 * 块设备 * 网络设备 2, 开发环境构建: * 交叉工具链构建 * NFS和tftp服务器安装 3, ...
随机推荐
- windows简单使用etcd
一.下载安装选择版本 https://github.com/coreos/etcd/releases 二.解压 三.首先开启etcd 1.进入在etcd解压的目录中 2.etcd.exe 没有erro ...
- Cocos2d-x项目移植到WP8系列之二:开篇
原文链接: http://www.cnblogs.com/zouzf/p/3970130.html 开发环境一笔带过吧,主板和CPU要支持虚拟化技术,要开启才行,装个64位win8.1系统,win8不 ...
- iOS清除缓存功能开发
在APP开发中,大量的图片或消息占用系统内存,造成一堆垃圾信息,所以开发清除缓存功能就显得必不可少了. 代码段1:获取文件的大小 - (long long) fileSizeAtPath:(NSStr ...
- iOS_数据存取(一)
目录: 一.沙盒机制 二.用户偏好设置 三.归档 一.沙盒机制 每个iOS应⽤都有⾃己的应用沙盒(应⽤沙盒就是⽂件系统⽬录),与其他文件系统隔离.应⽤必须待在⾃己的沙盒⾥,其他应用不能访问该应用沙盒的 ...
- JZ2440专用dnw 支持xp、win7、win8和win10系统【转】
本文转载自:https://blog.csdn.net/czg13548930186/article/details/76999152 学习于韦东山百问网公司 本文用于解决win7以上系统使用dnw难 ...
- python 中文字符的处理
刚开始学习python的时候,都是对这英文的翻译书学习的.没有解除到中文编码的相关问题,直到自己用python去做相关的项目的时候才发先中文编码问题真的非常头疼啊.这里分享一下本人所了解的一些经验. ...
- Fatal error: cannot create 'R_TempDir'
[user@mgmt dir]$ R Fatal error: cannot create 'R_TempDir' [user@mgmt dir]$ ll -ad /tmp drwxrwxrwt. 2 ...
- Mssql 比较好的写法
DECLARE @date DATETIME= '2016-11-01'; DECLARE @date2 DATETIME= DATEADD(day, 1, @date); Declare @1 Ta ...
- Swagger自动生成接口文档
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://mave ...
- Linux上SFTP用法
SFTP简介 sftp是一个交互式的文件传输协议,类似于ftp,但它进行加密传输,比ftp更安全. SFTP用法 localhost 从远程主机获取文件或目录到本地目录下 sftp>get /h ...