RAID 1+0

[Marco A.]

Hello,

It is possible set up RAID 1+0 under 11.31 without additional software, etc ? if so, how ?

Can someone help me with this ?

Best regards,

Marc'0

[Tim Nelson]

A psuedo 1+0 is possible with LVM and Mirror/UX ( but wait you said no additional software).

Some newer model servers have SAS controllers which are capable of raid 1 but no 0 ). I believe the P500 controllers can do 0+1.

How about VxVM ?? It is there...

[Robert-Jan Goossens]

Hi Marc,

Yes i believe you can use vxvm (Veritas volume manager)

VERITAS Volume Manager Features
Striping
Mirroring of user-data disks (QuickStart does include root mirroring)
Striping + mirroring (RAID 0+1)
Mirrored stripes (RAID 1+0)
RAID-5
RAID-5 with logging
Log-based mirror recovery (dirty region logging)
SmartSync (Oracle resilvering)
Hot-sparing/hot relocation
Dynamic multipathing (DMP)
Online data migration
Snapshots
Task monitoring
Online relayout

The base vxvm version is free, you can use it
to create a raid set on your vg00 (rootdg) only.

Hope this helps,
Robert-Jan

www.software.hp.com

[Marco A.]

Hello Tim,

Actually it's with lvm and mirror disk UX, additional software I meant ..hmm ...smartarray or something like that.

I got a couple of disk enclosures and want to set up RAID 1+0 using mirroring, but don't know what the procedure.

Regards,

Marco

[Marco A.]

Look guys,

I have 2 12 disks enclosures, my idea is mirror from one enc to another enc and then stripe, but I'm not sure about how is the right procedure.

Regards,

Marc'0

[Tim Nelson · Accepted solution]

Check out Robert-Jan's post first.

If you choose not to pursue that then yes if you have Mirror/UX you can do what is called distributed extent based striping with mirror.

This is not a traditional 2k, 4k, 8k.. stripe. The striping is done by lv extent which is based on the lvsize determined at creation time with minium of 2MB ( or was it 4MB). You will not have the granularity of the KB size but I have used this for years with great success. 4 146GB drives striped and mirrored to another 4 using ds2100. It performs almost as good as SAN attach array minus the cache benefits.

Read the vgcreate man page escpecially the -D and -s options.

Basically pvcreate all disks,
vgcreate and add all disks to vg.
edit /etc/lvmpvg and put 4 in each group PV1, PV2. Split them by controller.

Then when creating lvs,
lvcreate -L size -D y -s g -n name /dev/vgxx
newfs and you are done.

Must remember to use the same lvcreate command for all lvols.

Cons:
-cannot add new disks to grouping without rebuilding all lvols
-replacing an almost/partially failed disk requires you reduce the mirror, reduce the disk, add the new disk and remirror all lvols ( this could be up to 600GB of lvols if useing 146GB drives)

Best of luck.

[Marco A.]

Thank you Tim and Rob,

is 4 the max number of disk for mirroring and striping ?

So I have 12 disk in each enclosure, then I can make 6 VG's, 4 disk each, right ? or can I add more space for it. Those VG's are going to be used for oracle.

Regards,

Marco,

[Tim Nelson]

No limit ( except the ones imposed in the vg limits like max pv and max lv ).

I just used 4x4 as an example.

Keep in mind that the bigger it is the harder it is to admin, troubleshoot, recover... )

As with any other advise, pick some healty place in the middle, do 6x6 maybe.. your choice.

[Patrick Wallek]

I thought I read somewhere that LVM & MirrorDisk allowed a true mirrored stripe with 11.31.

I don't have an 11.31 system to test this with, but you should check the 'lvcreate' and/or 'lvextend' man pages and see if they talk about this.

[James R. Ferguson]

Hi:

Patrick remembers correctly. In 11.31, LVM allows striping and mirroring:

http://www.docs.hp.com/en/LVM-11iv3features/LVM_New_Features_11iv3.pdf

This is back-ported to 11.23 with patch PHKL_36745 (along with PHCO_36744 and PHCO_36746).

Regards!

...JRF...

[Marco A.]

hmm ...

I'm reading at the document and the man pages and I don't find anything regarding that.

hmm ...I think it's the same config posted in this forum not ?

Regards,

Marc'0

[Patrick Wallek]

Have a read starting of page 9 of the document link that James posted.

It talks specifically about creating RAID 0+1 / 1+0 sets.

Here is the command they use:
lvcreate -L 90 -i 2 -I 64 -m 1 /dev/vgtest

Naturally all parameters can be changed, but you should get the basics of the command.

[Marco A.]

Hello,

Thank you guys, you have pointed me to the right track.

Really appreciate your help,

Best regards,

Marc'0