LVM and VxVM

What to do with a failed disk from a SAN...

 
Jonathan Caplette_1
Super Advisor

What to do with a failed disk from a SAN...

Hi guys,

I've an EVA 3000 to share disk with my HP-UX 11i box. On my HP-UX box I have a filesystem that is mounted on a disk (from EVA 3000) that have failed.

In my EVA I've a Vdisk that is presented to my HP-UX box, this Vdisk is in Vraid0, that same Vdisk is using only one disk (hardware). Unfortunately that disk failed. So I called to have it replaced...

I don't have currently the new disk...

Now I wanted to know how on the HP-UX side, with LVM it will react, if I change the disk...

Currently the Vdisk is part of a VG that it only have that disk on, and only one LV that is currently mounted. I can't access my filesystem where the LV is mounted, normal, but I wanted to know, when I will change the physical disk in the EVA, how will LVm react to that?? I cannot unmount the filesystem for now... How could I solve this problem???

Regards
12 REPLIES 12
Alzhy
Honored Contributor

Re: What to do with a failed disk from a SAN...

Well Jonathan.. I guess you can bid your data good bye. VRAID0 has no protection at all from any physical disk failure. If it were VRAID10 or VRAID5 - any single (or double?) disk failure would have ensured your VDISK (or LUN) safe and HP-UX will happily continue to operate.

I guess at this time VxFS (not LVM) is complaining of vxfs errors and it is possoble LVM still "sees" the disk but under SecurePath .. it is already failed.

Hakuna Matata.
Pete Randall
Outstanding Contributor

Re: What to do with a failed disk from a SAN...

Hi Jonathan,

Doesn't this Vdisk belong to some sort of RAID group that should protect your data? If that's the case, replacing the disk should start the rebuild process and all should be well. If not - well, I find it hard to believe that that could be the case.


Pete

Pete
Jonathan Caplette_1
Super Advisor

Re: What to do with a failed disk from a SAN...

If I want to restore my data on the disk... how could I do that... I need to replace the configuration in my vg???
Pete Randall
Outstanding Contributor

Re: What to do with a failed disk from a SAN...

Disregard my earlier comments. It sounds from what Nelson is saying as if you can set up non-RAID LUNs on the EVA. Interesting! I can't imagine why one would want to create JBOD on an expensive platform like the EVA, but I guess you learn something new everyday.


Pete

Pete
Alzhy
Honored Contributor

Re: What to do with a failed disk from a SAN...

If your VDISK is to its own VG -- then you will need to recreate your VG.

If it is part of a VG along with other disks (or PVs or LUNs).. then consider the LVOLS that were on that VDISK gone.. you will need to lvremove those LVOLS, vgreduce the VDISK out of the VG, mobve in back the new VDISK (after the VRAID is fixed/disk replaced on the EVA) and recerate the LVOLS.. then you will need to restore from backup...

Sorry but this is the only way...

May I ask -- what prompted your enviroment to pick VRAID0 VDISKS? Is this a production box? If it is - you should have used VRAID10 or VRAID5...

Hakuna Matata.
Jonathan Caplette_1
Super Advisor

Re: What to do with a failed disk from a SAN...

It was the only disk on Vraid0... I don't know why I just get involved with that client!! :S I would not have do that either!
Uwe Zessin
Honored Contributor

Re: What to do with a failed disk from a SAN...

A minor correction...

virtual disks are always distributed over all physical disks within a disk group (minor exception for VRAID-1, which uses disks in pairs). It will not be using "only one disk (hardware)".


It is clear that this makes VRAID-0 less reliable if you put more disks into a disk group. A single disk failes and you loose (1/number of disks in your disk group) of the data. Replacing a physical disk on the EVA will not make your data available again.

The only way to retrieve it is by restoring from backup or try a recovery if you have any host-based RAID mechanism on top (your description doesn't make me confident that you have - I am afraid you will have to restart from scratch).
.
Jonathan Caplette_1
Super Advisor

Re: What to do with a failed disk from a SAN...

The filesystem is currently used to keep Ignite archives this server is a developpement box and it is used as an ignite server...

I've a backup of the ignite archives that I can restore... But I need to umount my filesystem and recreate the all of the vg?
Alzhy
Honored Contributor

Re: What to do with a failed disk from a SAN...

Yes.
Hakuna Matata.