2TB HDD Compatibility with PE2950

Question

Hello,

I would like to know if the PE2950 will recognize HDD capacities larger than 2TB. We are looking at setting up a server which will require a lot of storage, hence the need for the larger 3 or 4TB HDD. We will be using RAID10 along with FreeNAS OS. We will be populating the server with either (6) 3.5" 3TB HDD (usable capacity ~8.2TB) or (4) 3.5" 4TB HDD (usable capacity ~7.3TB).

I am new to servers, but from what I currently understand is that the server will limit the recognized space before the OS will. I've seen that the PERC controllers limit at 12TB, would this be before or after RAID configuration? For example, will (6) 3TB only be recognized as 12TB for RAID0, but ~9TB for RAID1? Also, then if the server has PERC5 or PERC6, will it recognize the 18TB or the 16TB?

Additionally, I believe the OS will also be handling the RAID, so I do not know if the software and RAID controller will have any conflicts.

I read that the HDD will require Dell firmware. If we use third party drives (e.g., Seagate or WD; not Dell), can this still be done? (From my understanding, the server will recognize third party HDD, but using the PERC will not recognize them?)

(Information source: http://en.community.dell.com/support-forums/servers/f/906/p/19435838/20049100.aspx)

I appreciate any and all help. Thanks.

Daniel My · Accepted Answer

Hello osirisguy

There is not a supported method for performing what you want. The PERC controllers supported in the 2950 do not support drives larger than 2TB. A drive larger than 2TB installed on a PERC 5/6 will either only display as a 2TB HDD or it may not be detected at all. Functionality will be trial and error for unsupported configurations.

I would like to know if the PE2950 will recognize HDD capacities larger than 2TB.

No. The only way it will is with an H700 or newer PERC. There are community members that have successfully installed these controllers in older systems, but it is not a validated/supported configuration.

For example, will (6) 3TB only be recognized as 12TB for RAID0, but ~9TB for RAID1?

A 3 drive RAID 1 is not possible, but I understand what you are asking. Yes, the OS only sees the available space. Drives used for parity or mirroring are not presented to the OS. As far as the OS is concerned those drives do not exist.

Additionally, I believe the OS will also be handling the RAID, so I do not know if the software and RAID controller will have any conflicts.

The OS does not handle the RAID, but it does need to be able to properly communicate with the RAID controller. It communicates via the driver within the OS. I would suggest finding out if the driver is compatible with your OS. If your OS is similar to a supported OS like RHEL then it will likely work.

I read that the HDD will require Dell firmware. If we use third party drives (e.g., Seagate or WD; not Dell), can this still be done?

Dell drives are not required on our servers. You may encounter communication issues with non-Dell drives, but we do not force the use of our drives.

Thanks

theflash1932 · Accepted Answer

Under no circumstances can the PERC see more than 2TB of a disk ... It is a design limitation of that generation of controller (regardless of brand - PERC, LSI, etc) ... Just pretend they are 2TB, because as far as the PERC is concerned, that is all they are.

Daniel My · Accepted Answer

In total I'll have 18TB total using RAID0 (i think there was also a typo in my last post). But if it is recognized, only 12TB will show.

Correct, if the drives are detected by the controller and functional they will be detected as 2TB HDDs for a total of 12TB.

However, the same number and size HDD configured for RAID1 will only give me 9TB.

Incorrect, you will get half of the space. The total space detected will be 6x2TB for 12TB. 6TB will be used for mirroring and 6TB will be usable space presented to the operating system. This will be in a configuration of 3 RAID 1 arrays.

I guess the better question would be does using higher RAID levels that keep me under the 12TB work for the PERC. Even though total capacity is more than 12TB

No, you are not fully understanding where the limitation lies. The limitation has nothing to do with the RAID level or any limitation of RAID array size. As theflash1932 pointed out the limitation is with the HDDs. The controller is not capable of addressing over 2TB of space on a HDD. Any drive larger than 2TB will either not be detected or will be detected as a 2TB HDD.

Even though total capacity is more than 12TB, usable capacity will be much less than that using RAID10, which fits into the requirement space. Or is a 3TB still to big, no matter how you "cut" it?

The 2TB limitation has nothing to do with RAID level. Even if you set the drives up in single drive RAID 0s they will never be seen as anything larger than 2TB. Even before you create a RAID array with the drive it will not be presented as anything larger than 2TB. RAID level does not matter in the 2TB HDD limitation.

Daniel My · Accepted Answer

Is it possible to purchase, I believe it is the PowerVault series, and just attach them to the PowerEdge 2950 to increase the end capacity?

Yes, you may want to create a new thread in the PowerVault forums to get better information on what is required. The 2950 supports a SAS5E that you can use to attach to an external storage unit. It will present the virtual disks/HDDs to the operating system as if they were installed internally.

OsirisGuy · Answer

Thank you.

So it seems that I can try using a H700/800 to recognize larger drives, but it's not guaranteed to work. I am not familiar with the various PERCs out there, so I will have to read up on those.

As for my example when comparing RAID0 and 1, I should have cleared up my question a bit. Let's say I'm using the PERC5/6 and (6) 3TB HDD. In total I'll have 18TB total using RAID0 (i think there was also a typo in my last post). But if it is recognized, only 12TB will show. However, the same number and size HDD configured for RAID1 will only give me 9TB. I guess the better question would be does using higher RAID levels that keep me under the 12TB work for the PERC. Even though total capacity is more than 12TB, usable capacity will be much less than that using RAID10, which fits into the requirement space. Or is a 3TB still to big, no matter how you "cut" it?

I will have to make sure the software will work, I expect it will, but I am not certain.

Thanks.

OsirisGuy · Answer

Thanks to both of you. I'm still trying to wrap my head around all the details.

I see now if I want to use anything larger than 2TB, I'll need to use a newer generation H700 RAID controller. Even so, Dell does not support this configuration.

So if I may throw out another idea and ask,

What about expanding the storage for the server? Is it possible to purchase, I believe it is the PowerVault series, and just attach them to the PowerEdge 2950 to increase the end capacity? Instead of (6) 2TB in just the server, it would be that, plus (X) 2TB in one of the PowerVaults? Would this additional storage, as long as each HDD is 2TB or less, be recognized? And how difficult will it be to add a PowerVault to a server?

One of the reasons I'm sticking with the 2950 is because I know of a few coming out of service that I may be able to get my hands on.

OsirisGuy · Answer

Thanks again. I will go ahead and ask in the PowerVault forums.

theflash1932 · Answer

Please see the response in your original post.

webstyler · Answer

Hello

I read the Daniel's answer and see that is also a verified answer.

So, PowerEdge 2950 with PERC 6/i could by read without problem HD with size 2TB, right ?

We need to install 6 HD 2TB and build a RAID 10, but not sure if bios could read this.

Best regards and thanks for any help / suggest

webstyler · Answer

Hello Daniel

Thanks for clarification

What we would like is to install FreeNas on usb stick, after add disk array of 6TB to configuration.

In this way we should not have any problems

if you have any suggestion is appreciated

Thanks

Daniel My · Answer

So, PowerEdge 2950 with PERC 6/i could by read without problem HD with size 2TB, right ?

We need to install 6 HD 2TB and build a RAID 10, but not sure if bios could read this.

Yes, a PERC 6 supports HDDs up to 2TB in HDD size. A 6x2TB HDD RAID 10 will work fine as a data array on a 2950, but you can't install the operating system on it. In order to boot from a RAID array larger than 2TB the system BIOS needs to support UEFI. UEFI support was not added to our servers until 11th generation. The 2950 is a 9th generation server.

Thanks

OsirisGuy · Answer

Just to give an update on what we ended with.

Our original plan was to use (8) Seagate ES.3 Constellation drives in an external array, however, the array (sorry I can't remember the model number) would not work with the Seagate. The HDD required Dell's firmware. Instead we did (5) of the HDD in the PE2950 and used RAID 5 (the PE2950 will be a back up server for us), giving us around 7TB of storage. We loaded Windows Server 2012 R2 on. We haven't transferred files yet to it, but I haven't heard any problems from the IT guys.

webstyler · Answer

We plan to use one of this series

SEAGATE	CONSTELLATION ES 3,5"	ST32000645NS	2TB 3.5" 7200rpm 64MB SATA 6Gb/s CONSTELLATION ES
SEAGATE	CONSTELLATION ES 3,5"	ST32000646NS	2TB 3.5" 7200rpm 64MB SATA 6Gb/s with SED CONSTELLATION ES
SEAGATE	CONSTELLATION 3,5"	ST2000NM0011	2TB 3.5" 7200rpm 64MB SATA CONSTELLATION ES

How to check compatibility with 2950 and PERC 6 before buy ?

Thanks

theflash1932 · Answer

The 2TB limitation in question is an MBR limitation, not a limitation of the hardware, although the PERC 6 DOES have a hardware-imposed limit on individual hard drive size of 2TB (for the same reason as the OS/MBR issue).

Windows cannot use a disk that is larger than 2TB, unless it is converted to a GPT disk.
Windows cannot BOOT to a GPT disk, unless it is installed on a UEFI-enabled system.
The PE 2950 does NOT support UEFI, so there is no way to BOOT to a GPT "disk" on a 2950, hence no way to boot to a "disk" that is larger than 2TB.

Keep in mind that the 2TB limit on the controller is a per-physical-disk limit; there is no practical limit on the size of an array/virtual disk (combined disks) as far as the controller is concerned.

sprunace · Answer

I am an orthodontist by trade and I dabble in computers but I found a solution for the 2TB limitation that seems to work quite well for me in my office. I recently purchased a 2950 III that has a perc 6i controller. It is populated with (6) 1TB Constellation Hard Drives. So regardless of how we tried to configure the drives in the raid controller Bios the computer would only recognize 2TB.

I even purchased a perc H700 and installed it and still ran into the same problem. So I created (2) Virtual Disks on the raid controller. The first VD was a (2 drives) raid (1) configuration (1TB partition) which I installed Server 2012 OS on the C drive. Then for the remaining (4) drives I created a second VD on the same controller and gave that a raid (5) configuration for almost 3TB. I booted up the computer went into Drive Manager and saw the second VD that was listed as "unallocated".

When I initialized this drive it gave me the option of either using a MBR partiion or GPT. It then stated that if I use the MBR I can not use the entire drive I would only be able to use up to 2TB (Drive E). I chose the GPT configuration and the system formatted the disk and I was able to access the disk at it's full capacity which is my (E) drive. After that I used Hyper V to create (2) VMs but I instructed them to be installed on the (E) drive. Each VM now has a 1TB capacity. So I have almost 1TB remaining on drive (E) to use for additional storage or to create more VM's if I chose to add them.

This setup appears to give me a dual layer of protection because even in the unlikely event I lose my entire raid 1 array I still have my data intact on the second VD which is in a raid 5 configuration. We just ordered a MD1000 (Perc 6i external DAS card) to use as a backup and additional storage. I figure when we run out of data space on the VM's I can push them over to the MD1000 and then recreate the (2) VM's with larger hard drive space and then pull them (VM's) back over from the MD1000. We currently use Carbonite as a cloud option and HP Media Smart Media server as our onsite backup. I hope I was helpful.

PowerEdge HDD/SCSI/RAID

>2TB HDD Compatibility with PE2950

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