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goppi
Enthusiast
Enthusiast

Storage Layout Advice

Hi.

We have a customer who needs more that 8 spindles within a ESXi 5.1 server to get enough IOPS out of it.

The problem is that the server hardware we are using normally (HP ProLiant DL380 gen.8) is only able to have 8 spindels connected to one controller. If you choose the 16-SFF model you have to put in a second HBA to handle the additional 8 spindles resulting in the fact that you can not combine all disks into one array.

Is it possible to combine two logical discs (two arrays of  8 disks each) into one datastore so that the load is spreaded evenly between the two arrays?

Or are there other possibilities?

Maybe anone has experience with the DL380 25-SFF (which should be capable of doing this) or maybe there is a different supported HBA from HP which is able to combine the two cages (8 HD each) into on array.

Thanks for your suggestions.

Cheers.

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8 Replies
ep4p
Enthusiast
Enthusiast

Install ESX on a SD card. Works perfectly and some server offer backup SD as well.

--ep4p

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jfrappier
Enthusiast
Enthusiast

There are worse things than having two separate datastores each with 8 disks.  I typically don't like having TOO many disks.  Also having a single RAID5 with all your hosts on it can easily be saturated by 1 or 2 VMs causing problems with the other VMs versus manually balancing.

As the other poster mentioned, you could install to SD or USB, make sure if you are not already sending log files to some syslog service make sure you do if you install to USB.... actually just make sure you do period!

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goppi
Enthusiast
Enthusiast

Thanks for your advices.

But the problem is not where to install ESXi (SD or not) but to have a datastore spread across more than 8 disks.

I agree that normally there is nothing wrong to simply have 2 datastores, but the problem with this customer is

that there is one VM which needs more than 8 disks to get as much IOPS as possible for that one VM.

RAID-5 is not an option at all as it scales bad on write performance esp. on vSphere so config

would be RAID-10.

What about having 2 extents for one datastore?

Will a single vmdk be spread across both extends and balanced "quite" evenly IO-wise?

I know there are much bad things being written about extents but IMHO much of that

seems to be based on rumors, missunderstandings, and simply fear of the unknown.

Cheers.

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jfrappier
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Enthusiast

If your IOPS are that high, rather than over-complicating the environment, why not just get a few SSDs?  They are fairly inexpensive in comparison to performance problems, or worse extended outages due to troubleshooting a one off configuration.

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jfrappier
Enthusiast
Enthusiast

If your IOPS are that high, rather than over-complicating the environment, why not just get a few SSDs? They are fairly inexpensive in comparison to performance problems, or worse extended outages due to troubleshooting a one off configuration.

goppi
Enthusiast
Enthusiast

Problem is that I have no long term experience with SSDs on server side, so I'm somewhat cautious to recommend that, but you advice is valid and something to think about.

Not overcomplicating things is good practise also.

Cheers.

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Josh26
Virtuoso
Virtuoso

Jon wrote:

If your IOPS are that high, rather than over-complicating the environment, why not just get a few SSDs?  They are fairly inexpensive in comparison to performance problems, or worse extended outages due to troubleshooting a one off configuration.

+1

Pushing past eight disks just in the interests of more IOPS on this hardware is already complicating things more than just buying some SSDs.

How specific is the need and number of IOPS, or is it just "I want more" ?

You do have the 2GB FBWC right?

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goppi
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Enthusiast

Pushing past eight disks just in the interests of more IOPS on this hardware is already complicating things more than just buying some SSDs.

How specific is the need and number of IOPS, or is it just "I want more" ?

You do have the 2GB FBWC right?

Why is more than 8 disk on this hardware overcomplicating things?

We are running those boxes with 8 disk already for some customers and there is nothing wrong with it.

Of course the 2 GB FBWC would be choosen.

Maybe the 25-SFF model would be an option, but I have no experience with that.

Or choose the 16-SFF model but then you have to operate two HBAs and

have to find a different way to spread the load

I've seen that SSDs are not that inexpencive - for one 200 GB SSD I get eight 146GB 15k disks.

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