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Compaq SA-5i: More performance thru logical drives?

ak_
Advisor

Compaq SA-5i: More performance thru logical drives?

Situation: two scsi drives on 5i.
Will i get higher performance thru creating logical drives on RAID 1+0, or is it better to have only one. I dont really think that the way with several logical drives will increase datatransfer rates, or?
Generally what could be reason to use the option of logical drives on only two physical drives?
6 REPLIES
Donald Kok
Respected Contributor

Re: Compaq SA-5i: More performance thru logical drives?

Hi ak,

raid 0 is striping
raid 1 is mirroring

so for raid 1+0 you need a minimum of 4 disks.
with 2 disks you have to choose between striping or mirroring.

If you want data redundancy / High availability you go for mirroring.
If you want performance you choose striping.

Hope this helps
Donald
My systems are 100% Murphy Compliant. Guaranteed!!!
ak_
Advisor

Re: Compaq SA-5i: More performance thru logical drives?

Thank You Donald for you reply,
that's is what i also ment.
So what you would say, the compaq array utility gives me an option to create RAID1+0 on only 2 drives (i wonder how but it is so), should i create several logical drives on this RAID1+0 Array?
Leif Halvarsson_2
Honored Contributor

Re: Compaq SA-5i: More performance thru logical drives?

Hi

Mirroring disks can increase read performance (as data can be read from either of the disks).It will also add security as one of the disks can fail witout data loss. But write performance can decrease as data has to be written to both disks.

Striping disks can increase both write and read performance but decrease security (compared to a single disk) as you lose all data if either of the disks fails.

There can be several reasons to create logical drives. Perhaps the most common is that you wart to create more then one filesystem.
ak_
Advisor

Re: Compaq SA-5i: More performance thru logical drives?

Thanks Leif,

the way i go is: i will create a RAID1+0 on two drives, with a little beat fantasy i can imagine that the technology is also usable for only 2 drives. The question without answer is: will i get more perfortmance thru creating of more then one logical drives on this RAID1+0 Array?




Donald Kok
Respected Contributor

Re: Compaq SA-5i: More performance thru logical drives?

Hi,

Maybe you can check what the amount of diskspace is of your raid1+0. If it is the

- sum of the 2 disks: it actualy stripes, and performance will increase.
- the amount of 1 disk: it actualy mirrors and there might be a little read gain.

Both ways there is not to expect a transfergain when applying logical drives. Actually I except a little loss of speed, since every abstractionlayer adds a little overhead which has to be handeled by the cpu.

Goodluck
Donald
My systems are 100% Murphy Compliant. Guaranteed!!!
ak_
Advisor

Re: Compaq SA-5i: More performance thru logical drives?

Hi Donald,

1.i got capacity from one drive available. It seems to be mirrored. As i wrote before with liitle beat fantasy i can imagine that the two drives will be mirrored and striped at same time like this: Drive1: Blocks A B and on Drive 2 Blocks B A. I dont really know, but i think it could be so designed.

2. yes, i agree with your meaning that the creating of logical drives will maybe generally decrease the performance. I think i will stay by one logical drive solution.

Thanks