HPE 2042 - Disk Grouping Setup Quesiton

[HPE2042User]

Can we please ask a quick couple of questions regarding disk setup/allocation for our HPE 2024? The unit is not yet in production so we are able to tear down / test etc at the moment. 

DISKS:

3 x 400GB SSD,

13 X 900GB 10k SAS. (One as a Hot Spare)

We were planning to have our SSD in a RAID5 disk gorup and the SAS disk in one RAID10 disk group. This would give us the speed and capacity required. 

Reading the best practice white papers, it is recommended to balance the controllers with equal disk groups. If we were to create one large RAID10 group with our 12 disks and assign this to one controller, then assign the SSD RAID5 to the other controller this would be sharing the load across the controllers but they would not be equally balanced.

If we were to split our 12 x SAS drives into 2 equal disk 6disk RAID10 groups then we could balance these equally across 2 controllers but.....

a) would we then end up with 2 smaller volumes instead of one large volume?

b) would we lose IOPS as less spindles etc.?

Also what would we then do with the SSD RAID5 group, which controller would this be assigned to?

We could (if we really had to) purchase a 4th SSD and then split them into 2 disk RAID1 groups and then balance them on each controller, but again would we then end up with 2 smaller volumes.?

Can anyone please recommend which way they would go with our disk setup.

1 Controller for one big RAID10 for the 10k SAS and 1 controller assigned for the SSD?

Many thanks

[giladzzz]

hi

first of all you must consider if you are using virtual or linear disk group

if you are using virtual pool and you have one more SSD disk you can 

create tiering using regular and SSD disks in the same pool but you need 

a licnese for that. also you can use the SSD disks as read cache ( no license required)

and then you can split what you have between controllers ( read cache can be in raid 0)

read HPE MSA 1040 2040 SMU Reference Guide

http://h20566.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c04220794&docLocale=en_US

also in the best practice guide you will see some information.

Regards

give a KUDO if this helps

[HPE2042User]

Thanks for the reply,

"f you are using virtual pool and you have one more SSD disk you can create tiering using regular and SSD disks in the same pool but you need a license for that"

We are using Virtual disk groups and the 2042 comes with the tiering licence. Are you saying that the only way to achieve this is by adding one more SSD, then assign 1 pair of SSD into pool A and 6 SAS into Pool A.. Then do the same with Pool B ?

Can we not have SSD in Pool A and SAS in Pool B and have the virtual pool with automatic tiering?

"also you can use the SSD disks as read cache ( no license required)"

We looked at the caching option but this would only give us a read performance gains where as a RAID5 would give us read & write gains?

We are trying to setup the array to follow the best practice guidelines but looking at all the possible ways to achieve this.

[giladzzz]

Hi

if you want to use tiering with you have these posiblities

1) create one virtual pool and use all your disks including the SSD with tiering

2) create one virtual pool with tiering and another without tiering

3) add another SSD disk and create two poolls with tiering

you are right about caching it only improves random reads

Regards

[Cali]

>> We are using Virtual disk groups and the 2042 comes with the tiering licence. Are you saying that the only way to achieve this is by adding one more SSD, then assign 1 pair of SSD into pool A and 6 SAS into Pool A.. Then do the same with Pool B ?

Yes, if you want to use both Controllers.

Or, put all the SSD + SAS Disk in one Pool A and Controller B do nothing until Controller A fails.

[HPE2042User]

"create one virtual pool and use all your disks including the SSD with tiering"

When in "Add disk Group" and select "Virtual" you cannot add different types of disk? Is this what you meant?

"Or, put all the SSD + SAS Disk in one Pool A and Controller B do nothing until Controller A fails."

This would mean that we would have a huge rebuild time if a disk was to fail, also the system would be unbalanced and we wouldnt get any gain from the dual controllers built in systems/caching etc.

Q1. Will the system teir between 2 different pools? e.g. Controller One (pool1) Raid5 SSD (Performance Tier) and Controller Two (pool2) Raid10 SAS (Standard Tier) drives. ??

Q2. Is it possible to use the dual controllers and still have one large "Volume" that covers both sets of Virtual Pools? So the hosts see one disk volume?

[giladzzz]

hi

Re: HPE 2042 - Disk Grouping Setup Quesiton[ New ]

"create one virtual pool and use all your disks including the SSD with tiering"

When in "Add disk Group" and select "Virtual" you cannot add different types of disk? Is this what you meant?

 when you create a virtual pool you create inside virtual disk groups if you want to use tiering create one virtual disk group with SAS disks and add to the pool another virtual disk group with SSD.

Q1: you can not tier between pools tiering is done between virtual disk groups in the same pool.

Q2: you can not create ""volumes"" between two pools.

Regards

Give A KUDO if this helps

[HPE2042User]

Thank you, 

So say we have a tier of SSD and SAS.  3 x SSD in RAID5 and 6 x SAS in RAID10 on the same pool/controller.

If the data is tiered across the whole volume, what happens if we have a double SSD failure? Does this mean that as the data is spread across all disks that we lose all data from both SSD and SAS drive groups? Even though the RAID10 would still show as optimal, wouldn’t it only contain parts of the tiered data?

In the case of a SSD drive failure, does the 2042 have something in place that would maybe evacuate the tiered data back to the other available pool to prevent loss? E.g. an SSD drive fails so the SSD disk group is showing as degraded, will it proactively move the data back to the SAS disk group?

Thanks for the replies :)