topic Re: Raid 5 Question ? in StoreVirtual Storage

Raid 5 Question ?

Danel_1 — Tue, 24 May 2011 07:49:23 GMT

Hi ,

Is anyone know how work the netraid5 volumes.

in 4 nodes Cluster , the provisionning size for one volume (full provis.)is the same for a Netraid10 or netraid5 (single parity)volume ?

I don't find documantation about this.

Thanks

Didier DANEL

Re: Raid 5 Question ?

Bart_Heungens — Wed, 25 May 2011 18:10:02 GMT

I do not know exactly what you mean but I suppose it is the following:

With network RAID 10 (before it was called replication level 2) with 4 nodes you will loose 2 nodes because of the RAID 10 replication.

With network RAID 5, 3 nodes will be used to write blocks of data, the 4th node will be used for the parity block.

So with RAID 5 you have more effective space available as with RAID 10. With RAID 5 you loose the disk space of 1 node, with RAID 10 it is 50%.

FYI RAID 5 is possible from 4 nodes on, RAID 6 is available starting from 6 nodes...

Re: Raid 5 Question ?

Johan Guldmyr — Thu, 26 May 2011 03:53:27 GMT

Is the parity spread out between the nodes?

Re: Raid 5 Question ?

Danel_1 — Thu, 26 May 2011 04:17:18 GMT

In fact the netraid 5 volumes(full provisionning) with 4 nodes consume exactly the same space that the netraid 10 volume

I don't understand , because if 3 nodes are used for data blocks and one node for Parity block , only 25% of space shoulf be lost.

thanks

Didier D.

Re: Raid 5 Question ?

Bart_Heungens — Thu, 26 May 2011 20:18:44 GMT

This is indeed the normal space usage being 25% lost with 4 nodes.

Can you provide some screenshots?

I assume you created a single site cluster and not a multi site?

Re: Raid 5 Question ?

Jitun — Fri, 27 May 2011 02:21:53 GMT

Under SANiQ 9.0 you only require 3 nodes for implementing network RAID 5 and 5 nodes for n/w RAID 6

I would recommend n/w RAID 5 only is your rate of change of the volume is 0-10%/day
Mostly Archival volumes, Large File shares, Remote Copy in DR Sites.
Volumes are mostly Read.

It delivers approximately 60% utilization of raw disk capacity assuming disk RAID 5 in storage nodes plus Network RAID 5 across nodes.

Re: Raid 5 Question ?

Danel_1 — Fri, 27 May 2011 04:26:41 GMT

ok ,
I will take screenshots asap.
Yes the cluster is standard .
do you have some documents or white papers about block distribution for Raid5 ...

thank you

Re: Raid 5 Question ?

Bart_Heungens — Fri, 27 May 2011 20:29:59 GMT

I have some screenshots from the HP training material which I am not allowed to shate unfortenatelly...
But it is simpel:
RAID 5 is 3 data blocks and & parity block (parity blocks spread accross the 4 nodes)
RAID 6 is 4 data blocks and 2 parity blocks
(parity blocks spread accross the 6 nodes)

I'll see if I can find public documents with the drawings...

Re: Raid 5 Question ?

Danel_1 — Sat, 28 May 2011 03:38:49 GMT

Hi Bart ,

can you to send me the internal pointer
didier.danel@hp.com

Thank you

Re: Raid 5 Question ?

Jitun — Thu, 02 Jun 2011 07:47:30 GMT

Sent u the email.
Hope it helps.