Recommended number of VMDK files for Virtual Appliances

[Anonymous]

I'm curious about something regarding SA Virtual Appliances.

If you have calculated that you need a 5TB database (doesn't matter which one for the purpose of this question), what is the recommend configuration in terms of VMDK files?

Do I have 1 x 5TB VMDK file or 5 x 1TB VMDKs assigned the LVM storage group for the database in question?

Thanks.

[JohnSnider]

Well it all depends on what the SA virtual appliance is running on and what that platform is using for storage.  If you are using an ESXi that is connected to a SAN, that is already configured for read/write optimization (ie. Many raid groups in many luns, with many metaluns, so you are hitting across multiples of disks for any one operations to spread the load, then it really doesn't matter which way you go, for simplicity just a 5 TB chunk of the SAN storage presented to you would do.  on the opposite end of the spectrum, if you have a standalone JBOD (lets say for example a 15 1TB disk JBOD) that you are using a SAS RAID controller to connect to, you would want to create a 6 disk RAID5 group (or however you want to slice it up) and present that to the VM as a single disk, 

It just all depends on what you have to work with, if you have a SAN on the backend, then it should already be configured to spread writes across multiple physical disks through it's configuration, so you would just need to make a single 5TB VMDK on that you would then user pvcreate/vgcreate/lvcreate to make your usable LVM.

[Anonymous]

Thanks for the reply John, that helps.

We are using ESXi servers with multipath Fibre fabric to a NetApp based SAN. So it sounds like a single VMDK for the file size I need wont be an issue.

Cheers.

[KhaledGamal]

Hi Jeremy,

I would  go with John's recommendation. Regarding your setup 1 VMDK would be the correct way to go.

Best regards

Khaled

[Anonymous]

Quick follow on question.

Would it be 1 VMDK for each database or 1 VMDK for the VolGroup that is then split via LVM for each DB.

As an example if I have the following space requirements:

PacketDB = 3TB

MetaDB = 2TB

SessionDB = 1TB

And they are all part of VolGroup01, which VMDK layout would be the best (I think I know what the answer will be).

1 x 3TB VMDK for PacketDB

1 x 2TB VMDK for MetaDB

1 x 1TB VMDK for SessionDB

or

1 x 5TB VMDK for VolGroup01 that then gets split in 3,2,1TB for each of the databases.

Thanks.

[KhaledGamal · Accepted solution]

Hi Jeremy,

The good thing about LVMs in Linux is that it doesn't matter where it takes from as long there is space in the Volume group. What I recommend and it is just a recommendation as both will work fine is to have one VMDK and assign it to a Volume group and then you can divide the databases to whatever size you want for each one.  The important thing is to have a logical volume for each database at the end with the size you require.

Hope this helps!

Best regards

Khaled

[Anonymous]

Thanks again Khaled, the 1 VMDK approach is where I was leaning toward as well. I guess from a VM point of view it would require less IOPS as it's only accessing of file as opposed to multiple.

[KhaledGamal]

You are always welcome.

Please don't hesitate to reach out in the future if any assistance is needed.

Best regards

Khaled

[Anonymous]

Hi Khaled,

I have a follow on question if you dont mind. I think I already know the answer but would like some clarification.

So in my example, I have a VMDK of 100GB. I increased the VMDK space to 200GB.

Should I bother trying to expand the existing partition or just create another partition to consume the free space and then just add that to the LVM VolGroup?

[KhaledGamal]

Hi Jeremy,

Both options will work but the easier one is to create a new partition and after that just add the new partition to the Volume group. After that you will have the Volume group with the bigger size and then you can adjust the logical volumes as you wish.

Note that when expanding the logical volume, you will have to expand the file system within the logical volume.

Hope this helps!

Best regards

Khaled