Q: Online resizing ext3 FS

Q: Online resizing ext3 FS

[Chris Osicki]

Hi

I apologize in advance for asking a question not really appropriate
for this mailing list, but I couldn't find a better place with lots of
people managing lots of disk space. 

The question:
Has anyone of you been using ext2online to resize (large) ext3 filesystems?
I have to do it going from 500GB to 1TB on a productive system I was
wondering if you have some horror/success stories.
I'm using RHEL4/U4 (kernel 2.6.9) on this system.

Thanks for your time.

Regards,
Chris

UNIX System Engineer
Swisscom Mobile Ltd.
Switzerland

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Re: [linux-lvm] Q: Online resizing ext3 FS

[Tomasz Chmielewski]

Chris Osicki schrieb:
> Hi
> 
> I apologize in advance for asking a question not really appropriate
> for this mailing list, but I couldn't find a better place with lots of
> people managing lots of disk space. 
> 
> The question:
> Has anyone of you been using ext2online to resize (large) ext3 filesystems?
> I have to do it going from 500GB to 1TB on a productive system I was
> wondering if you have some horror/success stories.
> I'm using RHEL4/U4 (kernel 2.6.9) on this system.

Yes, I tried to online resize a similar filesystem (600 MB to 1.2 TB) 
and it didn't work.

At some point, resize2fs would just exit with errors.
I tried to do it several times before I figured out what's missing; 
sometimes, I interrupted the process with ctrl+c. No data loss occurred.

To do an online ext3 resize, the filesystem needs a "resize_inode" 
feature. You can check the features with dumpe2fs:

# dumpe2fs -h /dev/sda1
(...)
Filesystem features:      has_journal resize_inode dir_index filetype 
needs_recovery sparse_super large_file
(...)

This flag is added by default only in the recent versions of e2progs 
(1.39 and later AFAIR); before, it had to be specified manually. So with 
RHEL4, you may be out of luck.


In the end, I had to to an offline resize.


I had this volume mirrored on another machine, so I didn't worry that 
much though.


Also, to resize a filesystem of that size you would need plenty of RAM 
(if you have about 1 GB RAM free, it should be just enough; otherwise, 
your machine will be swapping, and the process will take longer).
Before, I tried to resize it on a machine with 256 MB and several 
snapshots; resize2fs was killed because of OOM, and still, no data loss.


If you have that an old kernel, take care if you're using snapshots; I 
believe they are stable only as of 2.6.22 (before 2.6.22 snapshots 
needed a lot of RAM; before 2.6.18 there were problems with snapshots 
removing etc.).


Would be good to add some of that info to LVM HOWTO.


-- 
Tomasz Chmielewski
http://wpkg.org

RE: [linux-lvm] Q: Online resizing ext3 FS

[Hiren Joshi]

Sorry for the top quoting, I'm new to outlook =)

We did something similar, as the lv grows (with ext2online) the snapshot
will start filling up. If the resize fails, you will not be able to
(easily) revert directly back to the logical volume. This is because as
you start copying stuff back, the snapshot will be filling up. If you
want to be 100% safe, I would say go for some near line device that can
store 500G and backup to that!
HTH

-----Original Message-----
From: linux-lvm-bounces@redhat.com [mailto:linux-lvm-bounces@redhat.com]
On Behalf Of Stuart D. Gathman
Sent: 12 September 2007 21:04
To: LVM general discussion and development
Cc: linux-raid@vger.kernel.org
Subject: RE: [linux-lvm] Q: Online resizing ext3 FS

On Wed, 12 Sep 2007, Hiren Joshi wrote:

> Has anyone of you been using ext2online to resize (large) ext3 
> filesystems?
> I have to do it going from 500GB to 1TB on a productive system I was 
> wondering if you have some horror/success stories.
> I'm using RHEL4/U4 (kernel 2.6.9) on this system.

This brings up an LVM related question I've had.  Can I do this:

  1) take snapshot of 500GB LV
  2) resize source LV to 1TB
  3) run ext2online
  4a) resize succeeds - remove shapshot
  4b) resize fails horribly - copy shapshot to LV and restart
    4b.1) is there a way to "revert" the source LV to the snapshot?
    	(without allocating snapshot as big as source LV)

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703
591-6154 "Confutatis maledictis, flammis acribus addictis" - background
song for a Microsoft sponsored "Where do you want to go from here?"
commercial.

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Re: [linux-lvm] Q: Online resizing ext3 FS

[Goswin von Brederlow]

Tomasz Chmielewski <mangoo@wpkg.org> writes:

> Chris Osicki schrieb:
>> Hi
>>
>> I apologize in advance for asking a question not really appropriate
>> for this mailing list, but I couldn't find a better place with lots of
>> people managing lots of disk space.
>>
>> The question:
>> Has anyone of you been using ext2online to resize (large) ext3 filesystems?
>> I have to do it going from 500GB to 1TB on a productive system I was
>> wondering if you have some horror/success stories.
>> I'm using RHEL4/U4 (kernel 2.6.9) on this system.

That kernel seems to be a bit old. Better upgrade first.

I did some resizes in that size range. Although just adding 50-200GB
not doubling the size in one go. But I see no reason it should
fail. Growing the fs was always quick (a minute or two) and
painless. Maybe because I have used -Tlargefile4 for mke2fs so the
amount of inodes is drastically reduced.

> Yes, I tried to online resize a similar filesystem (600 MB to 1.2 TB)
> and it didn't work.
>
> At some point, resize2fs would just exit with errors.
> I tried to do it several times before I figured out what's missing;
> sometimes, I interrupted the process with ctrl+c. No data loss
> occurred.
>
> To do an online ext3 resize, the filesystem needs a "resize_inode"
> feature. You can check the features with dumpe2fs:

So was that what you were missing or did some other error occur?

I tried to resize an fs without resize_inode and it just plain told me
and abrted.

MfG
        Goswin

Re: [linux-lvm] Q: Online resizing ext3 FS

[Goswin von Brederlow]

"Stuart D. Gathman" <stuart@bmsi.com> writes:

> On Wed, 12 Sep 2007, Hiren Joshi wrote:
>
>> Has anyone of you been using ext2online to resize (large) ext3
>> filesystems?
>> I have to do it going from 500GB to 1TB on a productive system I was
>> wondering if you have some horror/success stories.
>> I'm using RHEL4/U4 (kernel 2.6.9) on this system.
>
> This brings up an LVM related question I've had.  Can I do this:
>
>   1) take snapshot of 500GB LV
>   2) resize source LV to 1TB
>   3) run ext2online
>   4a) resize succeeds - remove shapshot
>   4b) resize fails horribly - copy shapshot to LV and restart
>     4b.1) is there a way to "revert" the source LV to the snapshot?
>     	(without allocating snapshot as big as source LV)

Why do you resize the LV if you want to test it first? Give the
snapshot the extra 500G and resize that. If it fails you just remove
the snapshot and try again.

If it succeeds then you can do it the other way around and resize for
real.

MfG
        Goswin

Re: [linux-lvm] Q: Online resizing ext3 FS

[Tomasz Chmielewski]

Goswin von Brederlow schrieb:
> Tomasz Chmielewski <mangoo@wpkg.org> writes:

(...)

>> Yes, I tried to online resize a similar filesystem (600 MB to 1.2 TB)
>> and it didn't work.
>>
>> At some point, resize2fs would just exit with errors.
>> I tried to do it several times before I figured out what's missing;
>> sometimes, I interrupted the process with ctrl+c. No data loss
>> occurred.
>>
>> To do an online ext3 resize, the filesystem needs a "resize_inode"
>> feature. You can check the features with dumpe2fs:
> 
> So was that what you were missing or did some other error occur?
> 
> I tried to resize an fs without resize_inode and it just plain told me
> and abrted.

It was working for some time (15 or 30 minutes?), the fs grew a couple 
of gigabytes, and then it exited with an error. At first I thought it's 
because the fs might need fsck, but after I did fsck, it didn't help - 
next online tries didn't increase the fs anymore.


-- 
Tomasz Chmielewski
http://wpkg.org

Re: [linux-lvm] Q: Online resizing ext3 FS

[Bill Davidsen]

Goswin von Brederlow wrote:
> Tomasz Chmielewski <mangoo@wpkg.org> writes:
>
>   
>> Chris Osicki schrieb:
>>     
>>> Hi
>>>
>>> I apologize in advance for asking a question not really appropriate
>>> for this mailing list, but I couldn't find a better place with lots of
>>> people managing lots of disk space.
>>>
>>> The question:
>>> Has anyone of you been using ext2online to resize (large) ext3 filesystems?
>>> I have to do it going from 500GB to 1TB on a productive system I was
>>> wondering if you have some horror/success stories.
>>> I'm using RHEL4/U4 (kernel 2.6.9) on this system.
>>>       
>
> That kernel seems to be a bit old. Better upgrade first.
>   

You don't upgrade when using the stable releases... that's the whole 
idea, you don't have to worry about a new versions of anything, the bugs 
and security issues are backported, but the version stays the same. 
Highly desirable for "must work" systems, no so nice for doing cutting 
edge stuff using nice features you don't have. :-(

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

Re: [linux-lvm] Q: Online resizing ext3 FS

[Goswin von Brederlow]

Bill Davidsen <davidsen@tmr.com> writes:

> Goswin von Brederlow wrote:
>>>> I'm using RHEL4/U4 (kernel 2.6.9) on this system.
>>>>
>>
>> That kernel seems to be a bit old. Better upgrade first.
>>
>
> You don't upgrade when using the stable releases... that's the whole
> idea, you don't have to worry about a new versions of anything, the
> bugs and security issues are backported, but the version stays the
> same. Highly desirable for "must work" systems, no so nice for doing
> cutting edge stuff using nice features you don't have. :-(

Debian has 2.6.18 in stable. And they Debian stable is way too old to
use. :)

MfG
        Goswin