Some questions about Data stores and LUN

[zeebahi]

Hi everyone,

I am learnng VM sphere, have some questions:

1) Does single LUN can have exactly single disk or it can have more?

2) Assuming single LUN can have multiple disks, Let's say we have two disks :

D1, I/0=100/sec

D2 ,I/0=100/sec

These two disks are mapped to LUN0. Further more, LUN0 is mapped to DataStore0.

What is the maximum I/O Datastore0 can handle? is it 200/sec because it contains two disks each with 100/sec I/O?

3) Let say we have two Datastores:

Datastores1 has one LUN0 , LUN0 can support 100/sec I/O.

Datastores2 has two LUN1, LUN2, each LUN can support 100/sec I/O.

Will Datastore2 support max 200/sec I/O total ?

4) Please see the following set up.

EXSI:1

VMk1 9.9.9.9 --VSW1--VMNIC1---SW1-----9.9.9.10-ISCSI TARGET( LUN)

Above VMK1 is used for storage, SW1 is dedicated switch for Storage. Should we enable JUMBO frame on SW1 and VSW1? What is VM's recommendation?

When I did the packet capture, I see a lot of full sized frames, each write operation can be up to 1M bytes of block. So if a VM performs a single Write of 1M bytes, it will require transmission of many IP packets. Considering this, enabling jumbo frames will reduce transmission of many frames needed for single Write.

I am curious about VM's recommendation if there is one.

Thanks and have a good weekend!!

[tayfundeger · Accepted solution]

I answer your questions.

1) The LUN can consist of one or more disks.

2) The read / write speed will change according to the RAID you have made on the physical server. If you set RAID 0 with the property you specified, yes you will get 200 / sec. But if you do RAID 1, you get 100 / Sec. So the amount of IOPS of each disk is of course important.

3) Depends on the RAID you have used.

4) You can activate the jumbo frame. You can review the following resource for ISCSI Storage.

Using Jumbo Frames with iSCSI