Dell Powervault MD3000i or Dell Equallogic PS4000XV 8 x 300GB SAS 15KRPM single controller

Posted on 2009-12-21
Last Modified: 2013-11-14
Hi, in a company they want to buy a SAN. The choices are seen in the title. Company is about 100 users. They want to use a virtualization. VMware or Hyper-V. Servers are 2 IBM x3650 servers and 1 x3550 server.
If it was up to me I would choose the Equallogic iSCSI SAN. But money is a main factor for the decicions to make. Programs will be Windows Server 2008, Exchange 2007 or 2010, SQL 2005 or 2008.
Does anybody have any experience with the Dell Powervault, Hyper-V in a production environment?

Question by:LeonesIT
    LVL 32

    Expert Comment

    I would go with the MD3000i simply because it has the ability for a larger expansion for storage(~90TB) and it has a high availability module to allow you to have four gigE ports for redundancy/connectivity.
    LVL 1

    Accepted Solution

    There are a few reasons you might want to go with one solution over the other - here are the quick reasons:

    Go with EqualLogic if:
     * You want replication offsite,
     * You want linear performance / capacity increases,
     * You need application consistent snapshots (VMware, Hyper-V, SQL, Exchange),
     * You need tiered storage - perhaps SSD, fast SAS, and SATA for a wide variety of performance needs.

    Go with the MD3000i if:
     * You don't need any of the above, and
     * You're on a real tight budget,
     * Snapshots don't necessarily need to be application consistent
     * You're much more concerned about price per GB than performance

    In your requirements, you mention that you will be running Hyper-V, Exchange, and SQL. When you snapshot these as part of your point-in-time recovery options, they may not be crash consistent at the application unless you use EqualLogic. That is to say, the snapshot function happens at the disk level, and isn't aware of your application. If there are items in your server's memory that have not yet been committed to disk when you issue your snapshot, those items in memory will not be recoverable. This could mean your database or virtual machines are at inconsistent states, and may need to be repaired. In contrast, with EqualLogic's Auto Snapshot Manager, all cached items are flushed to disk, and the caching functions are disabled while the snapshot is taking place. Afterwards, it is immediately re-enabled. This gives you consistency, and means fewer nights (ideally no night) repairing the databases should something go wrong.

    Now let's talk performance:

    Disks - a disk is a disk, so the base level for performance between an EqualLogic and an MD3000i are easily comparable: 8 15k disks in an EqualLogic will perform like 8 15k disks in an MD3000i (assuming disks are similar in performance specs). EqualLogic might use some performance-increasing methods of reading/writing the data, but I wouldn't bank on that magic as part of your decision.

    Caching - Beyond the disks' performance, there is caching. Any time you need to go above what your disks are physically capable of (talking about IO per Second), caching comes into play. The EqualLogic solution has 2GB of cache per controller, whereas the MD3000i has 512MB. An EqualLogic with the same disks as an MD3000i will perform better (noticeably) because of this.

    Bandwidth - EqualLogic controllers come with quite a few options. With the PS4000 model, you get dual GbE ports per controller (active/passive controllers) for 2Gb/s using multi-pathing. With the PS6000 and PS6500 models, you get quad GbE ports for 4Gb/s. With the PS6010 and PS6510 models, you get two 10GbE ports, giving you 20Gb/s using multi-pathing. This is significantly faster than Fibre Channel, and beats direct attached storage by a LONG shot. The MD3000i gives you 2 GbE ports per controller, much like the PS4000 series. In all the analysis I've done, bandwidth has NEVER been an issue. If there were a constraint at all, it'd much more likely be IOPS than bandwidth. I analyse the real performance numbers to get this information, and you should too just to be sure.

    I'd say there are some action items to help you determine which one you would want to go with, knowing the differences between the two:

    1) Analyse your current disk needs. Do you need more IOPS than 8 15k SAS disks can provide? If so, maybe 15 or 16 disks (MD3000i can only have 15) could provide them for you. If 8 is too little but 15 is overkill, the EqualLogic caching can save you there. Alternatively, you could use more disks in the MD3000i - anywhere between 1 and 15. DELL will help with this if you ask nicely!

    2) What kind of backups are required? If snapshots will be an integral part of your procedures, you should heavily consider EqualLogic because of the Auto Snapshot Manager. If you're handling backups another way, the MD3000i can do just fine. Don't forget that EqualLogic has the ability to offload backups from your main servers by connecting the volumes directly to your backup server to back up.

    3) Financial - yes, it's a huge deal. If you realize that for your performance requirements, an MD3000i is as expensive as (or very close to) the EqualLogic, go after the EqualLogic!

    4) Decision time. After the performance analysis and backup/financial considerations, just pick the one that fits. As long as the performance works, I'm sure you'll be happy with either one. We have clients who run both, some who run MD3000i only, and of course several who run the EqualLogic arrays. They are both fantastic options.

    My bias - I'm in love with EqualLogic. It's very easy to manage and performs with excellence. If you can swing an EqualLogic purchase for this, you'll see why I love it.

    -- Brad

    Author Comment

    Thanks Brad, this is really a good explanation. I am also pro Equallogic. But this is al about money....


    Expert Comment

    We have a very similar structure and put in a PV MD3000i with single controller & 2 PE2950s last October due to budget constraints. 2 weeks ago, we decided to add a 2nd controller to the MD3000i which I am regretting big time as the NVSRam update failed without highlighting any issues and corrupted the data across all disks. Dell had to completely wipe everything, recreate all virtual disks and groups and we had to restore entirely from backup (this wasn't too bad as we use Veeam Backup & Replication). After a complete rebuild by Dell with 2 controllers, we had a 2nd failure mid-week which also corrupted all the VMs (blue-screens, ntldr missing errors etc....). This time Dell admitted a faulty controller and removed it. To add insult to injury, the Veeam backups taken between the 2 failures were not able to be restored despite Veeam reporting the backups as successful. Luckily we managed to recover most of the VMs with a combination of many chkdsks, fixboot, fixmbr etc.... We ended up losing a lot of data and had to restore from the last good Veeam backup before the 1st failure. We are now back to a single controller and experiencing iSCSI timeouts across the board on most servers especially Exchange. I attempted to export 136KB of support logs for Dell yesterday and all VMs stopped responding for 5 minutes (luckily no data corruption this time). Needless to say we are currently in a battle with Dell to get some stable storage and the company have lost all confidence in the virtual infrastructure (nothing wrong with this but people don't understand).

    We are now contemplating replacing the MD3000i with a high spec box (possibly an Equalogic) that will allow SAN replication so we have SAN redundancy.

    The moral of the story is that cutting costs to meet an unachievable budget comes at a price and I would not go for the MD3000i with single, dual, triple or even bloody quadruple controllers! Your storage is your entire backbone when consolidating servers and this proves that just disk and controller redundancy is not necessarily enough. I hope this influences your decision making for this project if not too late :)



    Expert Comment


    I am facing the same situation of choosing MD3200i vs. EqualLogical PS4000XV. I think the MD3200i is a later version of MD3000i which has 4 GBe ports instead of two ports.

    After heard of Liam's story, I would probably choose EqualLogical instead to avoid losing data.

    thanks for the information.

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