[linux-lvm] Questions regarding LVM

[linux-lvm] Questions regarding LVM

[Vishal Verma -X (vishaver - Embedded Resource Group at Cisco)]

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Hello all,

 

    I am new to this mailing list. I have few questions regarding Linux
LVM, would appreciate if LVM gurus could answer.

 

 

1.       Under scenario where, several hard-drives are part of LVM
volume group and if one of hard-disk gets corrupted then would whole
volume group be inaccessible ?

What would be impact on volume group's filesystem ?

 

2.       From stability perspective, which version of LVM is better on
Linux kernel 2.6.x, LVM2 or LVM1 ?

 

Regards,

Vishal

 


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Re: [linux-lvm] Questions regarding LVM

[malahal]

Vishal Verma -X (vishaver - Embedded Resource Group at Cisco) [vishaver@cisco.com] wrote:
>    1.       Under scenario where, several hard-drives are part of LVM volume
>    group and if one of hard-disk gets corrupted then would whole volume group
>    be inaccessible ?

No.

>    What would be impact on volume group's filesystem ?

A volume group may have several file system images. You should have no
problem in accessing logical volumes (or file systems on them) that
don't include the corrupted/failed disk. Obviously, logical volumes that
include the corrupted/failed disk will have problems unless it is
a mirrored logical volume!

>    2.       From stability perspective, which version of LVM is better on
>    Linux kernel 2.6.x, LVM2 or LVM1 ?

I would go with LVM2.

Re: [linux-lvm] Questions regarding LVM

[Ray Morris]

> 1.       Under scenario where, several hard-drives are part of LVM
> volume group and if one of hard-disk gets corrupted then would whole
> volume group be inaccessible ?


See the --partial option.  See also vgcfgrestore. (rtfm)
Basically, if the drive is merely "corrupted" as you said,
there could be some currupted data.  If the drive is missing
or largely unuseable those extents are gone, so LVs with
important extents on that PV would have serious problems,
but LVs with no extents on that PV should be fine.  "Important"
extents means, for example, if a 400GB LV which is only 10%
full has only it's last couple on extents on the missing PV
that may not be a major problem, if no data is stored there
yet.  On the other hand, the first extent of the filesystem
probably contains very important information about the
filesystem as a whole, so if that first extent is unuseable
you're probably reduced to greping the LV, or using an automated
search tool that basically greps the LV - the same type of
tools used for undelete or corrupted disks without LVM.

> What would be impact on volume group's filesystem ?

    VGs don't have filesystems.  LVs do. This is the same
question as "if I'm NOT using LVM and parts of my drive go
bad what is the effect on the filesystem?" The ability to
salvage files from the filesystems of affected LVs depends
on how many extents are missing or corrupted, which extents
those are, and what type of filesystem is used.

    So in summary, LVM doesn't change much in terms of the
affect of a bad disk.  You should still have really solid
backups and probably use RAID.
--
Ray Morris
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On 12/03/2009 12:22:11 PM, Vishal Verma -X (vishaver - Embedded  
Resource Group at Cisco) wrote:
> Hello all,
> 
> 
> 
>     I am new to this mailing list. I have few questions regarding  
> Linux
> LVM, would appreciate if LVM gurus could answer.
> 
> 
> 
> 
> 
> 1.       Under scenario where, several hard-drives are part of LVM
> volume group and if one of hard-disk gets corrupted then would whole
> volume group be inaccessible ?
> 
> What would be impact on volume group's filesystem ?
> 
> 
> 
> 2.       From stability perspective, which version of LVM is better on
> Linux kernel 2.6.x, LVM2 or LVM1 ?
> 
> 
> 
> Regards,
> 
> Vishal
> 
> 
> 
> 

------quoted attachment------
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] Questions regarding LVM

[Stuart D. Gathman]

On Thu, 3 Dec 2009, Vishal Verma -X (vishaver - Embedded Resource Group at Cisco) wrote:

> 1.       Under scenario where, several hard-drives are part of LVM
> volume group and if one of hard-disk gets corrupted then would whole
> volume group be inaccessible ?

Short answer: it depends

Long answer: For raw plain hard drives, only logical volumes using the
affected drive are inaccessible.  Think of LVM as managing fancy run-time
expandable partitions.  You may wish to ensure that the LVM metadata (the LVM
equivalent of the partition table) is stored in multiple locations, or
frequently backed up from /etc/lvm.

More often, the "drives" that are part of LVM are software or hardware RAID
drives.  In addition, Linux LVM supports mirroring (RAID1) at the LV level
- although not yet as smoothly as other LVM systems.

> What would be impact on volume group's filesystem ?

Same as with any other partition that goes south.

> 2.       From stability perspective, which version of LVM is better on
> Linux kernel 2.6.x, LVM2 or LVM1 ?

LVM2

-- 
	      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.