XP512 questions

[Roger Baptiste]

hi,

I have some questions related to configuring a XP 512 array.

-> What is preferable - RAID 0/1 (mirror/stripe) or RAID 5 . I mean, is the RAID 0/1 performance GOOD on the XP?? That's because i have seen EMC's are mostly configured with RAID 1 , whereas the XP's i have come across were all on RAID 5 and even HP seems to suggest RAID 5.

-> IF i choose RAID 0/1 , will the M1 disks be on L1/R1 and M2 on L2/R2 ? or is there a different method ?

-> Next, how does the concept of EMulation mode works? There seems to be three basic modes,
OPEN-3 -> stripe size of 2.46 gb.
Open-8 -> stripe size of 7.3gb and
open-9 -> stripe of 7.4gb.
So, i would think that if i say i need open-3, all disks in the unit would be striped with 2.46 and the number of splits would be dependent on disk size (like in EMC).
But, it does not seem so in XP. It seems one can use different emulation modes. Will this not affect performance consistency across the RAID?

What is a
OPEN-K/3/8/9/E device?
OPEN-3/K*n OPen-3/K-CVS
LUSE-5
LUSE-7 etc etc.
I was reading the manuals, but couldn't get the full picture on what exactly these names denote. Where does K,E come from?
Is LUSE something like a metavolume of EMC??

-> Is there any choice/flexibility in picking DISKS for an ARRAY GROUP? I mean can we group disks from L1/R1/L2/R2 into an array group?
or would that be an overkill?

-> Any suggestions for stripe size, VG extent sizes etc?

Finally, is there any other utility other than
xpinfo to access XP. (for eg, emc has syminq, symdev, sympd...).

Thanks in advance and points guaranteed for responses! ;-)
-raj

[Bernd Reize]

Hi RajMan,

I can at least provide some answers to you:

- Both RAID0/1 and RAID5 are configured in the same physical way: 4 HDDs in the same Disk Frame and the same Disk Bay are called one RAID-Group, which can be 0/1 or 5.
Of course you can mix that, i.e. have 5 Raid-Groups with RAID5 and another five with RAID0/1

- OPEN Emulation
The stripe and split size are independant from the emulation mode, so they should not impact performance.
Which emulation you should choose depends mostly on the disk sizes you need for your hosts and the physical disk sizes within the XP512 - for 15/73/180 GB drives there are recommended OPEN Types to get the most useable space out of the disks.
The different sizes:
OPEN-3 2.461 GB
OPEN-8 7.348 GB
OPEN-9 7.385 GB
OPEN-E 14.568 GB
OPEN-L 36.436 GB
OPEN-M 47.171 GB

OPEN-K i've never heard of.

- CVS/LUSE you are right, they are similar the EMC's Meta Volumes. With CVS you can define smaller volumes (split OPENs), with LUSE you can define larger Volumes (i.e. OPEN-E*1/2/3...)

- You cannot customize the Array Groups, they are hard defined to four disks. But you can build LUSEs that spread over different array groups. But in my opinion you should not use this but host level sriping instead. Much more flexible.

- For stripe size (=stripe depth) HP recommends 64K, VG Extend size i'm not sure.

- There are some cli tools for BCVs and CA, but configuration can be done only via the GUI :-(

Hope that helps,
Bernd

[Hanniff Tingling]

Hi RajMan

Wow - you ask quite a bit of questions; I will try and answer as many as I can;

You Asked:

What is preferable - RAID 0/1 (mirror/stripe) or RAID 5 . I mean, is the RAID 0/1 performance GOOD on the XP?? That's because i have seen EMC's are mostly configured with RAID 1 , whereas the XP's i have come across were all on RAID 5 and even HP seems to suggest RAID 5.

My response:

I believe the RAID preference should be based on your unique circumstance. That is RAID 0 - stripe; high I/O access but very little amount of redundancy. RAID 1 - mirror but 'slower' I/O access however it provides you with great redundancy; RAID 0/1 combines both High Redundancy/Availability and fast I/O Access.
You can see now that it would depends on you requirements - it you need to write a large volume of data quickly and redundancy is not a concern - then RAID 0. (in short; speed vs security)

For RAID 5 - use at least 1 disk more than RAID 0/1. This aditional disk is for parity - So the first consideration is: You will need more disk for the same job - concern; cost. However, in RAID 5 - data is split and written between two or more disk simultaneously, I/O is increased over the other RAID configuration and also - it provides security and peace of mind since it also has parity written on a seperate drive;
Parity can be used to recover data; so RAID 5 is fast and very safe. So you will have to balance between cost (for the extra disks - for parity)and speed. It depends on your tolerance level.

If cost is not a factor RAID 5 all the way!!!
As far as I know, there aren't any differences because of RAID levels on the XP512 or the EMC. That is, if both Arrays has identical RAIDS, performance will not be better on one or the other because of RAID. performance differences will be because of other factors. XP512 performs much better than EMC under most maybe all circumstances. I must say though that the SVP system software on the EMCs are really cool!

I will end here and answer the other questions in another post.

Hope that help!

[Hanniff Tingling]

RajMan

ther you go --> Bernd answered some of your questions:

You Asked:

Finally, is there any other utility other than
xpinfo to access XP. (for eg, emc has syminq, symdev, sympd...).

My Response:

Yes there are several other utility/software bundles and plug-ins to access XPs. They are usually included with the package you order; for instance there is a product called AutoPATH XP; which allows you to configure failover I/O path among other stuff. It is included in the SureStore E autoPATH XP software for different platforms; ie. HP UX, AIX, Solaris etc. A utility called datapath "set, query etc") is provide. the only things is I find working with XP software really cool as you move various platforms - you pretty much have the same GUI and commands (with some exceptions)

For more info - check this link out.

http://www.hp.com/products1/storage/disk_arrays/xpstoragesw/index.html

Hope that help!

[Roger Baptiste]

Bernd,

Thanks for the response. Some more queries;-)

In RAID 0/1 -> Where do the M2 (mirror) disks
sit? Is it predefined (like in
EMC). For example, is
Diskbay on L1 mirrored to a
diskbay on R2 ?

In RAID 5 -> since 4Hdds can only belong to
a raid group, does that mean, max size of a
raid group would be 4*disksize*75% eg:
for disk size of 36Gb -> raidgroup would
be 4*36*3/4 = 108 Gb ?

OPEN Emulation modes ->
is it a term to define a LUN size, as seen by the system?? For eg, if i say i need
OPEN-3, would it mean that i get 3 Gb PV's(lun) at the system end?


thanks
-raj

[Roger Baptiste]

Haniff,



Actually, i think it is the reverse. In
Raid 0/1, each HDD has m1 and m2 (mirror disks). So, ever disk needs a mirror.
The usage would then be 50% of the Symm capactiy.

In Raid 5, every group needs a parity disk.
So, for a group of 4 disks, one disk is used
as parity. The usage would then be 75% of the
symm capacity.

With this, if there is enough $$ and capacity, RAID 0/1 is the way to go. But again, it depends on the design of a symm too. EMC seems suited for 0/1. I don't know about XP though.

-raj

[Insu Kim]

OPEN Emulation modes ->
is it a term to define a LUN size, as seen by the system?? For eg, if i say i need
OPEN-3, would it mean that i get 3 Gb PV's(lun) at the system end?

> The XP disk array can be designed for several kind of systems such as OPEN systems and Mainframe.
For example,
OPEN emulation (OPEN3,8,9,E, etc) is for OPEN systems and 339X emulation for Mainframe respectively so you need to select an emulation type appropriate for your purpose.
After formatting with OPEN-3, ioscan will display a 3GB device file.

Hope this helps,

[Insu Kim]

In RAID 5 -> since 4Hdds can only belong to
a raid group, does that mean, max size of a
raid group would be 4*disksize*75% eg:
for disk size of 36Gb -> raidgroup would
be 4*36*3/4 = 108 Gb ?

> For example,
A disk capacity is 47GB and 4 disks are configured with RAID5, OPEN-9 (7.004GB).

47GB * 3 = 141 GB ( Considered RAID5 )
141 GB / 7.004 = 20.131 EA(s),
ioscan will show you 20 LUNs, the total size would be,
20 * 7.004 = 140.08
As a result, you'll lose the remainder, (141-140.08).

This is not the exact caculation so you'll lose much more capacity than you thought it would be.
- I have no data at this time. sorry for this.

For the maximum use of capacity, HP will tell you which emulation you have to choose for a given disk drive like 47GB or 72GB.

Hope this helps,

[Victor BERRIDGE]

Forgot:
Load your XP512 with 73GB/10 rpm disks (I think HP P/N A5968AX) they are the best deal...

All the best
Victor