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Re: LUN Distribution Disk Group Striping in EVA 5000

 
Tom O'Toole
Respected Contributor

Re: LUN Distribution Disk Group Striping in EVA 5000

Uwe,

Sorry, I've been throwing around the term LUN to mean 'a presented vdisk' when I really mean (e.g.) VMS os_unit, your usage is of course correct. VMS (as of 7.3-2) does still only use one path per host. My impression until now was that even multiple hosts were all using the same controller port to the same unit (at least on Hsg80s). I guess it is easy enough for me to check on this for the hsg80 and eva5000.

Jeff,

I'm curious about the justification for creating numerous small storage sets and striping them at the host. The eva will stripe over all the disks is the group, so what is the point of this? If it is to load balance across paths, would not 4 vdisks per host device be enough?

Also, couldn't one buy several EVAs for the price of the other arrays you recommend? Just to add front end fibre ports approaches the price of another eva system. Anyway, it is strange that a single small eva is specified in this config.

rccmum,

To followup on Jeff's comment, you do have a fairly small configuration - 2C6D to connect all those systems. You have gotten only 56 15K drives. If you are not filling a configuration (240 drives), you get a faster system for the same price by buying 10K drives, since you get so many more of them/dollar. This is mentioned in the best practices paper.
Can you imagine if we used PCs to manage our enterprise systems? ... oops.
generic_1
Respected Contributor

Re: LUN Distribution Disk Group Striping in EVA 5000

By having many small disks in a san environment it allows the firmware algorymths to sense paterns like database reads so prefectching works better, because if you have larger disks it becomes more likely for requests for different IO are going to hit that lun confusing the software and making it a random and killing your prefetch. Also if you have more disks io requests wonnt stack up on that single initiator trying to reach that one or two huge disks/luns/virtual disk. The EVA by definition is supposed to move all this stuff around for you, but how efficient it is in reality youd have to test, or go by the whitepaper.

Why would I say Use something like a DMX, why not have 15k drives with more/faster cache, direct linked controllers that can share their I/O, an UPS insdie the frame, more fibers off of the controllers, and having seen higher reliability in practice, and that you've spent probably a million dollers on a superdome. Why cheap out on the slowest/greatest bottlneck you have left, being the disk.
generic_1
Respected Contributor

Re: LUN Distribution Disk Group Striping in EVA 5000

I have seen fiber channel disks go out with bad failures on the EVA5ks that cause the Controllers to shut down or crash at different sites we have. Its not pretty. Also, they should really have a built in ups with firmware management if they are being used in a large expensive highly available system. If you have low availability requirements and low IO EVA will work, but its not designed to be HP's high end, high availabilty product. Its more midtear, NAS would be your lowend.

High end locally attached disks would be the ideal because they dont have to share ;). SAN is supposed to bring cost efficiency and ease of management, and virutalizing large disks, although somethings I wonder about the cost efficient part :).

You can get way more fibers and controllers off of a DMX or XP even though they cost more, better prefetch software, more, faster cache, and more importantly more relieable.

I run DMX3000, symetrix, and XP1024 on our 7 Domes at my location, and PVlinks.
rccmum
Super Advisor

Re: LUN Distribution Disk Group Striping in EVA 5000


Waiting for Smart answers!!!! to questions mentioned.

Any suggestions for putting oracle 8i on EVA 5000? We would be migrating to oracle 9i later from 8i on the eva. can anyone suggest me to have some proactive things which could be done right away to ease migration at later stage?
rccmum
Super Advisor

Re: LUN Distribution Disk Group Striping in EVA 5000

Anybody there to put more comments on this thread and my questions??

Waiting for replies..
generic_1
Respected Contributor

Re: LUN Distribution Disk Group Striping in EVA 5000

If you put points on your previous replies Im sure youll See allot more information :). Click the assign points at the bottom if you are not familliar with the forums. I am guessing you are new member so welcome.

Cheers Jeff
Bill Costigan
Honored Contributor

Re: LUN Distribution Disk Group Striping in EVA 5000

One caution on LVM striping. I would do extent based striping not the native striping. If you stripe across 16 drives and then want to add more drives, you need to add another 16 drives (LUNs) because the stripe routines cannot handle changing the number of drives in a stripe.

If you did extent based striping, you could start striping across 16 LUNs and then later extend the VG by striping across an additional 4 LUNs.

Tom O'Toole
Respected Contributor

Re: LUN Distribution Disk Group Striping in EVA 5000

rccmum,

Seems to me you have gotten pretty good answers to all four questions you asked. Could you re-ask, in more detail, the questions you still have? Thanks.

Can you imagine if we used PCs to manage our enterprise systems? ... oops.
rccmum
Super Advisor

Re: LUN Distribution Disk Group Striping in EVA 5000

Guys , I have been curiously waiting for feedback for Gurus out there to this thread.
It made me understand EVA more closely...

Thanks all putting your comments on this thread, I appretiate your time and efforts.

Well , I have lot more questions on EVA 5000.
I would be creating new threads for them.