[linux-lvm] Manegeability with LVM

[linux-lvm] Manegeability with LVM

[Anders Widman]

Hello.

I have a system with 14 disks of diffenrent sizes (40-120GB).

As my need for diskspace increases all the time I was thinking of
using LVM so I could make use of all diskspace and grow/shrink/replace
drives as I need to.

The only downside to this is the possibility of massive dataloss if I
loose any of the 14 disks (drive fails to spin etc...). Would it be
possible to setup up a software redundancy like RAID5 with LVM so I
can keep this manageability LVM gives me?

I know this has been up in this list before, but I couldn't find a
suitable answer.

//Anders

Re: [linux-lvm] Manegeability with LVM

[José Luis Domingo López]

On Monday, 04 March 2002, at 23:00:10 +0100,
Anders Widman wrote:

> As my need for diskspace increases all the time I was thinking of
> using LVM so I could make use of all diskspace and grow/shrink/replace
> drives as I need to.
> 
Take into account that there are filesystem that by design doesn't
support shrinking of filessytems (e.g. XFS). Some others allow you to
both grow and shrink filesystems, but sometimes you will have to unmount
the filesystem before modifying its size.

On the LVM part, it was designed to allow growing and reducing LV sizes
without being necessary to put your machine in some "maintenance" state.

> The only downside to this is the possibility of massive dataloss if I
> loose any of the 14 disks (drive fails to spin etc...). Would it be
> possible to setup up a software redundancy like RAID5 with LVM so I
> can keep this manageability LVM gives me?
> 
Remember, nothing except regular _and_ verified backups of your valuable
data can guarantee that your data will survive a hardware _or_ software
error. I'm am not sure what I fear most, a damaged disk or a severe 
filesystem corruption. Some RAID levels give you additional hardware
failure protection, but other levels increase your chances of lossing
data. LVM can be seen as some sort of linear-RAID, and as such, usually
increases the probability of a broken disk destroying your data.

In other words, backups are (and will always be) the way to go.

-- 
Jos� Luis Domingo L�pez
Linux Registered User #189436     Debian Linux Woody (Linux 2.4.18-rc4aa1)
 
jdomingo AT internautas DOT org   =>  Spam at your own risk

Re: [linux-lvm] Manegeability with LVM

[Anders Widman]

> On Monday, 04 March 2002, at 23:00:10 +0100,
> Anders Widman wrote:

>> As my need for diskspace increases all the time I was thinking of
>> using LVM so I could make use of all diskspace and grow/shrink/replace
>> drives as I need to.
>> 
> Take into account that there are filesystem that by design doesn't
> support shrinking of filessytems (e.g. XFS). Some others allow you to
> both grow and shrink filesystems, but sometimes you will have to unmount
> the filesystem before modifying its size.

Yes, very true. I was thinking of using reiserfs which supports at
least offline resizing/shrinking.

> On the LVM part, it was designed to allow growing and reducing LV sizes
> without being necessary to put your machine in some "maintenance" state.

>> The only downside to this is the possibility of massive dataloss if I
>> loose any of the 14 disks (drive fails to spin etc...). Would it be
>> possible to setup up a software redundancy like RAID5 with LVM so I
>> can keep this manageability LVM gives me?
>> 
> Remember, nothing except regular _and_ verified backups of your valuable
> data can guarantee that your data will survive a hardware _or_ software
> error. I'm am not sure what I fear most, a damaged disk or a severe 
> filesystem corruption. Some RAID levels give you additional hardware
> failure protection, but other levels increase your chances of lossing
> data. LVM can be seen as some sort of linear-RAID, and as such, usually
> increases the probability of a broken disk destroying your data.

> In other words, backups are (and will always be) the way to go.

True. I do agree. Right now I don't have the "economy" to buy
additional hardware so I have to do the best thing with these drives
(with the possibility to add new ones or replace old ones for bigger
drives.).

//Anders

Re: [linux-lvm] Manegeability with LVM

[Austin Gonyou]

XFS does support shriking..but not with LVM. 

On Mon, 2002-03-04 at 16:34, José Luis Domingo López wrote:
> On Monday, 04 March 2002, at 23:00:10 +0100,
> Anders Widman wrote:
> 
> > As my need for diskspace increases all the time I was thinking of
> > using LVM so I could make use of all diskspace and grow/shrink/replace
> > drives as I need to.
> > 
> Take into account that there are filesystem that by design doesn't
> support shrinking of filessytems (e.g. XFS). Some others allow you to
> both grow and shrink filesystems, but sometimes you will have to unmount
> the filesystem before modifying its size.
> 
> On the LVM part, it was designed to allow growing and reducing LV sizes
> without being necessary to put your machine in some "maintenance" state.
> 
> > The only downside to this is the possibility of massive dataloss if I
> > loose any of the 14 disks (drive fails to spin etc...). Would it be
> > possible to setup up a software redundancy like RAID5 with LVM so I
> > can keep this manageability LVM gives me?
> > 
> Remember, nothing except regular _and_ verified backups of your valuable
> data can guarantee that your data will survive a hardware _or_ software
> error. I'm am not sure what I fear most, a damaged disk or a severe 
> filesystem corruption. Some RAID levels give you additional hardware
> failure protection, but other levels increase your chances of lossing
> data. LVM can be seen as some sort of linear-RAID, and as such, usually
> increases the probability of a broken disk destroying your data.
> 
> In other words, backups are (and will always be) the way to go.
> 
> -- 
> José Luis Domingo López
> Linux Registered User #189436     Debian Linux Woody (Linux
> 2.4.18-rc4aa1)
>  
> jdomingo AT internautas DOT org   =>  Spam at your own risk
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html
-- 
Austin Gonyou
Systems Architect, CCNA
Coremetrics, Inc.
Phone: 512-698-7250
email: austin@coremetrics.com

"It is the part of a good shepherd to shear his flock, not to skin it."
Latin Proverb

Re: [linux-lvm] Manegeability with LVM

[Goetz Bock]

On Mon, Mar 04 '02 at 18:33, Austin Gonyou wrote:
> XFS does support shriking..but not with LVM. 
How come, LVM is just an other block device, isn't it?

Cu,
    Goetz.

Re: [linux-lvm] Manegeability with LVM

[Heinz J . Mauelshagen]

On Tue, Mar 05, 2002 at 11:41:26AM +0100, Goetz Bock wrote:
> 
> On Mon, Mar 04 '02 at 18:33, Austin Gonyou wrote:
> > XFS does support shriking..but not with LVM. 
> How come, LVM is just an other block device, isn't it?

Right. If you could shrink an XFS filesystem, you can shrink
the logical volume afterwards.

I must have missed that one: since when does XFS support shrinking?

> 
> Cu,
>     Goetz.
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
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Re: [linux-lvm] Manegeability with LVM

[Martin K. Petersen]

>>>>> "Heinz" == Heinz J <Heinz> writes:

Heinz> On Tue, Mar 05, 2002 at 11:41:26AM +0100, Goetz Bock wrote:
>>
>> On Mon, Mar 04 '02 at 18:33, Austin Gonyou wrote:
>> > XFS does support shriking..but not with LVM.
>> How come, LVM is just an other block device, isn't it?

Heinz> Right. If you could shrink an XFS filesystem, you can shrink
Heinz> the logical volume afterwards.

Heinz> I must have missed that one: since when does XFS support
Heinz> shrinking?

It doesn't...

-- 
Martin K. Petersen, Principal Linux Consultant, Linuxcare, Inc.
mkp@linuxcare.com, http://www.linuxcare.com/
SGI XFS for Linux Developer, http://oss.sgi.com/projects/xfs/

Re: [linux-lvm] Manegeability with LVM

[Patrick Caulfield]

On Tue, Mar 05, 2002 at 09:14:11AM -0500, Martin K. Petersen wrote:
> >>>>> "Heinz" == Heinz J <Heinz> writes:
> 
> Heinz> On Tue, Mar 05, 2002 at 11:41:26AM +0100, Goetz Bock wrote:
> >>
> >> On Mon, Mar 04 '02 at 18:33, Austin Gonyou wrote:
> >> > XFS does support shriking..but not with LVM.
> >> How come, LVM is just an other block device, isn't it?
> 
> Heinz> Right. If you could shrink an XFS filesystem, you can shrink
> Heinz> the logical volume afterwards.
> 
> Heinz> I must have missed that one: since when does XFS support
> Heinz> shrinking?
> 
> It doesn't...

Does it support "shriking" though :^)

patrick

Re: [linux-lvm] Manegeability with LVM

[William Blunn]

> Would it be possible to setup up a software redundancy like RAID5 with
> LVM so I can keep this manageability LVM gives me?

Yes.

It's in the docs.

LVM can do (in effect) linear appending and RAID0 internally.

If you want RAID5, you just do it underneath LVM.

Create one or more RAID5 set(s) using RAID tools (not part of LVM). This
will give you one or more software RAID device(s).

Then create LVM PVs on the RAID devices. The rest is all normal LVM
stuff.

http://www.google.com/search?q=linux+software+raid

Bill
-- 
William H. Blunn - <bill+s.20020227@tao-group.com>
Tao
62/63 Suttons Business Park, Earley, READING, RG6 1AZ, United Kingdom
Tel: +44 118 901 2999 - Fax: +44 118 901 2963 - http://tao-group.com/