XP12000: Is there now a way for the array to present striped LDEVS - ala EVA?

[Alzhy]

Greetings!

Our XP12000 currently use Open-V LDEVs (our of 7+1 or 4+2 RAID sets). Additionally on the Hosts, webuild storage volumes consisting of 2 LDEVS each from diff ACPs and stripe them 8-ways.

Is there now an LDEV layout (LUSE?) that can present striped LDEVS as a stiped LUN to the host so host level striping is avoided and also lessen the number of LDEV/LUN presentations to a host?

With our EVA8100, we're dealing with signifiacntly small number of LUNS and can exact better performance (but no predictabioity of course)...

[Peter Mattei · Accepted solution]

Hi Nelson

The best way to distribute IO across an XP is using a volume manager and stripe across Ldevs on all available array groups.

If we do not have a volume manager able of striping (Windows, Linux etc) we usually set up RAID5 (28+4) groups. Here an Ldev stripes across 32 drives.

See the attached slides for reference.

Cheers
XP-Pete

[Alzhy]

Peter,

SO I take it that LDEV Interleaving via RAID5 (14+2P or 28+4P) *is* the only way that an LDEV can be carved with the most number of spindles w/o engaging a host based Volume Manager like VxVM?

Are there no RAID1 based LDEV interleaving aside from your 4+4 scheme?

I guess what I'm trying to come up is to lessen the number of LUNS on the servers whilst still having the performance. But I guess that's just essentially best practice still these days for Hitachi Based arrays - right?

If Only HP can come up with Firmware on the USP that will come close to the manageability and RAID flexibility of the EVA - I think that will really be the day man.

So I guess we are still on the right track then with an additional level of RAIDing (striping) with VxVM. I sometimes employ Layered VOlumes with VxVM to come up with storage volumes that engage more spindles .


Thanks!

[Alzhy]

BTW,

Your comparsative performance for read and write - are you actually sugegsting that customers are better off with RAID5 or RAID6 layouts compared to RAID10?

We've plans to actually convert from RAID 7+1/6+2 over to RAID1 4+4 in the hope of besting EVA8K performance and better scale our TB sized Databases for mixed load performance.

Do you think we'll be better off with RAID5 (7+1) or RAID 6 (6+2)?

[Peter Mattei]

If you have a volume manager on top of the XP with striping capabilities I recommend using either RAID5 7+1 or RAID1 2+2 basd Ldevs. They will give you best performance per disk.

The decission to choose wich is manly based on cost and write performance requirements.
While both have similar read performabnce RAID1 will have higher write performance.

I only recommend RAID5 28+4 for environments WITHOUT a volume manager capable of striping!!
28+4 has a slightly higher overhead in the XP than 7+1.

BTW: we have come up with new ways of doing it! But ....
this is only on the XP20/24000.
It is called Thin Provisioning (ThP) which allows the following:
1. presenting more capacity than actually physically present
2. provisioning of the LUN layout and capacities you expect in months or years from now.
3. striping in blocks of 42MB over a pool of Ldevs that can span a whole XP.

ThP comes very close to the EVA striping when it is used without overprovisioning!

Again, see the attached slides I created to explain ThP.

Cheers
XP-Pete