common questions-Storage architecture

[kunjuttan]

I am new to Storage architecture.I have some doubts reagardng storages in common ie not specific to HP storage.

1) In which scenario the raid-1 is best suited and in which scenario raid-5 is best suited.

2) Is there any performance difference can be achieved if I am using smaller size of LUNs ie if OS team require 500GB of space for their Fiesyatem, which will be the best option - to create a single 500GB or to create 50/100GB LUNs. And please let me know the reason for the same.

[Torsten.]

It all depends on the hardware used, but in general a RAID10 is faster than a RAID50, because there is no calculation needed; an array can do striping better/faster than the OS can do (better use a large LUN). But it depends on the array hardware ...

[kunjuttan]

I am using HP-EVA8K and EVA6K. We are defining raid1 and raid5 usually. AMong this which is better?

[Torsten.]

As said, a vraid1 is usually writing faster than a vraid5, but it needs more space. Since it using the same count of disks, the speed of reads should be similar.

[Johan Guldmyr]

1) In which scenario the raid-1 is best suited and in which scenario raid-5 is best suited.

RAID1 when you want fast writes and more reliable storage.
RAID5 when you want slower writes and cheap storage.

http://en.wikipedia.org/wiki/RAID#RAID_10_versus_RAID_5_in_Relational_Databases

The wikipedia entry has some nice information.

[Bhavnish_Kamboj]

Go to acnc.com

it will answer all your queries.

[Sheldon Smith]

As far as LUN size, older OS'es were sometimes limited in the number of IOs they could queue to a single LUN. To improve performance, one gave them several smaller LUNs. As far as I know, no operating system worth its salt these days has such a problem. In addition, since physical drives used to be small, one would present several to the OS which would bundle them together into a large logical volume; usually done by the OS's LVM (Logical Volume Manager).

These days, most operating systems have the ability to have many IOs going to its LUNs. Also, AFAIK, all newer file systems have the ability to deal with an expanding LUN. So there should be little or no difference in performance between one 500GB LUN vs. ten 50GB LUNs. And management will definitely be Much Easier.

It might help if you told us what Operating System (and version) and what applications (and version) you are planning on using.