Optimal Sector Size for Promise Pegasus R6

Discussion in 'Mac Accessories' started by randm, Aug 13, 2013.

  1. randm macrumors newbie

    Joined:
    Jul 11, 2012
    #1
    I got a Promise Pegasus R6 with 6 x 1TB drives. The Seagate ST4000DM000 4TB disks are now officially in the hardware compatibility list of the Pegasus R6. I am replacing all 6 1TB drives with 6 of the Seagate 4TB drives.
    I use RAID 5 for all 6 disks. I have Mac OS X 10.8.4. I use the R6 primarily for video editing, photo editing, and storing iTunes media (lots of large HD video).

    Some questions:

    1. When I create the logical disk, should I use the 512 byte sector size default, or should I use the 4KB sector size?

    2. In Disk Utility, one can specify the block size for the Pegasus disk. The default is 32KB. Is this block size unrelated to the sector size used to create the R6's logical disk?

    3. In Disk Utility, should I use a larger block size (large than 32KB). Can I just change the block size in Disk Utility without affecting the data in the R6's logical disk?

    4. For stripe size, the R6 default is 128KB. I plan on using 256KB stripe size. Yes, I know smaller files won't be spread across all the disks, but for my use (large video files, mainly), I was wondering if a larger strip size like 256KB would be better than the default 128KB.

    5. Another possible approach, rather than optimizing the aforementioned parameters, is to just stick with the defaults (512 byte sector size, 128KB stripe size, and 32KB Disk Utility block size), and not worry about it, if the performance differences would be negligible, since one school of thought is that maybe the default values are better tested by Promise and might be more reliable.

    I'd also like to hear from Promise Pegasus R6 & R4 users who purchased their units with 3TB or 4TB drives. Can you look at what stripe size was used by Promise?

    Thanks.
     
  2. nochnia macrumors member

    Joined:
    Jun 25, 2011
    #2
    I'm pretty interested in this too. If anyone knows more details about that - highly appreciated.
     
  3. flynz4 macrumors 68040

    Joined:
    Aug 9, 2009
    Location:
    Portland, OR
    #3
    I have an R4... and I am using the stock 2TB drives that came with the machine. I would personally recommended using the default for the reasons that you state. The R4/R6 is a fast box... and I would speculate that you are unlikely to feel any performance change. Stick with what is tested.

    /Jim
     
  4. randm thread starter macrumors newbie

    Joined:
    Jul 11, 2012
    #4
    I created my logical disk with 4Kb sector and 256Kb stripe size. I have 6 4TB disks in a RAID 5 array. Prior to creating my LD, I first upgraded to the June 2013 firmware, which has this fix:

    " Data integrity testing FAILED with OS 10.8.X if the sector size of LD other than 512 bytes"

    A Promise tech support person that I emailed with earlier said to just use the defaults since it is most tested, while another Promise tech support (this time someone I talked to on phone instead of email) said 4Kb is fine after he consulted with another more knowledgeable colleague.

    So far, 4Kb secors work fine for me, but I didn't do any performance testing.
     
  5. cinemaloha, Sep 4, 2013
    Last edited: Sep 4, 2013

    cinemaloha macrumors newbie

    cinemaloha

    Joined:
    Sep 4, 2013
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    Online
    #5
    Hi randm,

    This is my first post on MacRumors, I'm mainly on the FCP.co forum since I'm using Final Cut Pro X (FCPX).

    Thank you for posting your feedback on the the R6 with the Seagate ST4000DM000 4 TB Drives. I'm researching if I should upgrade to 24 TB since I'm at 80% capacity on my 12 TB R6. I'm concerned about reliability and read/write speeds on RAID 5.

    Also, could you post screenshots running the Blackmagic Disk Speed Test or other benchmarking app or just let me know what read/write speeds your getting as well as reliability.

    I was reading the Pegasus Manual (PDF) and had a few questions for you since you've already upgraded.
    1. On page 49, did you use 'Express Configuration' and use 'Application Type' as 'File Server' or 'Video Stream'? My projects are around 1.5 to 2 TB at times so I'm not sure which option would be more efficient.
    2. On page 88, I intended to use 256 KB stripe size as you did since I'm mainly editing HD Video but wanted to know your logic behind that and why not 512 KB or 1 MB? For me, 256 KB was the middle available and did not want to compromise read/write speeds. The 4 KB sector size was self explanatory because I want more efficient use of my disk drive.
    3. On page 98, did you enable 'Read Ahead' for the 'Read Cache Policy'? The manual states that it "can increase read performance" but won't really know without real world test.


    My R6 12 TB RAID 5 info:
    • (6 x 2 TB Drives)
    • Stripe Size is 128 KB
    • Sector Size is 512 KB
    • June 20, 2013 (5.02.0000.98) Firmware

    Sorry if this is demanding but my research did not come up with much and yours is the first solid information I've come across. Thank you in advance.
     
  6. randm thread starter macrumors newbie

    Joined:
    Jul 11, 2012
    #6
    1. I didn't use Express Configuration. After I had put the 6 4TB drives in the R6, when I tried to run the Wizard, the Automatic and Express buttons were grayed out. Only the Advanced button was available.

    Below are the steps that I used for setting up m6 6 x 4TB RAID 5 array:
    ------------
    - Change Mac settings to not sleep (just in case it shouldn't sleep during synchronization)
    - Unlock Promise Utility to allow changes
    - Disk Array->Create Disk Array
    - Subsystem Information->Clear Statistics
    - Wizard->Advanced Configuration:
    Create Disk Array:
    Alias: <= I didn't enter anything
    Enable Media Patrol: check (checked by default)
    Enable PDM: check (checked by default)
    Click on the 6 disks (from 1 to 6):
    IDs of Physical Drives Selected: 1,2,3,4,5,6
    Create Logical Drive:
    Alias: <= I didn't enter anything for this
    RAID Level: RAID5
    Capacity: 20 TB (automatically changed to 20TB when I selected RAID5 above)
    Stripe: 256K (default was 128 KB. Choices were 64KB, 128KB, 256KB, 512KB, 1MB)
    Sector: 4KB (default was 512 Bytes. Choices were 512 Bytes, 1KB, 2KB, 4KB)
    Read Policy: ReadAhead (default)
    Write Policy: WriteBack (default)
    Format: check (default)
    Then clicked "Add", so new drive shows up in right side of GUI
    Create Spare Drive:
    I didn't select any drives for spare

    Then, I clicked on "Submit"
    After a few seconds, I got "Disk array was created successfully"
    Then, I clicked on "Finish"

    Synchronization took about 30 hours.
    ---------------

    Most of my files are video and music files. I also thought about possibly using more than 256KB stripe size. I searched online and someone did some testing on an R6 and his conclusion was that stripe size didn't make that much difference, but someone else's test (not with an R6 but some other RAID device), changing stripe size can make 10% or so difference in performance. Not sure who to believe. I suppose I could have done some testing with different stripe sizes, but given that it takes 30 hours to synchronize the drive, I didn't have time/inclination to do the testing. So, I figured that 128KB was the default size, and doubling it to 256KB was a safe enough bet as opposed to "going on a limb" and assuming I should use 512KB or 1MB. I suppose if one had a lot of small files, a smaller stripe size helps (but for me, most files are larger). Anyway, without actual, definitive testing on large sizes (e.g. 512kB or 1MB), I figured 256KB was a good enough compromise.

    As indicated above, I used ReadAhead and WriteBack. My R6 is on a UPS, so I'm okay using WriteBack.

    Also attached is a snapshot of the Disk Speed Test. I ran this test with my R6 and a 2011 MacBook Air (still waiting for the upcoming Mac Pro to replace my old 2008 Mac Pro). You can also search online for test results for the Seagate ST4000DM000 4TB drive. It is (IIRC) a 5900RPM drive, but maybe it doesn't make much difference when in a RAID array of 6 drives (as opposed to a standalone internal drive, which would matter more). It's not as fast as the 3TB Seagate ST3000DM001, but it's still pretty good (and I like that it's cool and quiet). Also, 4TB means the data is packed more densely than a 2TB drive so the drive heads can theoretically get more data at a time. Also keep in mind that your R6 is 80% full. As you may know, the more full a disk is, the less the performance (given that each rotation of the platter delivers less data the closer you get to the center of the disk).

    I don't use Final Cut Pro (plan to when I have some time to play with it and when I upgrade my old Mac Pro). This is the first time I've run Disk Speed Test. How do the numbers look based on what you've seen with the 6 X 2TB R6? I ran the test for a few minutes (not sure how long I'm supposed to run it).
     

    Attached Files:

  7. cinemaloha, Sep 4, 2013
    Last edited: Sep 4, 2013

    cinemaloha macrumors newbie

    cinemaloha

    Joined:
    Sep 4, 2013
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    Online
    #7
    Excellent procedure write-up. Thanks for that. Once I am finished with all my projects, I will upgrade to 24 TB with 1 MB Stripe Size (for the extreme settings test) and post the results. If true, the 10% performance increase will help.

    I am also on a UPS (APC ES 350) so I will use the same configuration with the ReadAhead and WriteBack.

    You are correct, the ST4000DM000 is 5900 RPM Spindle Speed but like you said it'll run cooler with less noise. Maybe the 1 MB Stripe Size will make up for any performance decrease.

    My write speed is 673 MB/s. My read speed is 592.3 Mb/s. Does it matter that it's a MBAir that we have a 25% & 20% (respectively) difference? My iMac specs in signature. I'm exactly at 78.71% capacity. My test is with 5 GB stress setting and ran it for 3 rounds of read/write. I can live with your posted speeds for more storage space - since 4K cameras are coming out weekly, I'm prepping myself for it.

    Based on the keynote video - the new Mac Pro, Mavericks, and FCPX 10.1 (fingers-crossed) are made for each other so I'm also excited for it.

    Again, many thanks for the guidance.
     

    Attached Files:

  8. randm, Sep 4, 2013
    Last edited: Sep 4, 2013

    randm thread starter macrumors newbie

    Joined:
    Jul 11, 2012
    #8
    Is your R6 configured with RAID 5?

    Please run the Disk Speed Test once you've configured your R6. I'm interested in how 1 MB stripe size does. Ideally, you'd want to run the test with 1MB stripe size and also with a smaller stripe size like 128KB or 256KB using the same hardware (4TB disks and same Mac). However, I don't know if you would want to re-create the logical drive for different stripe sizes since it takes a long time to synchronize the drives.

    The previous test that I did was using a Mid 2011 MacBook Air (1.8GHz/4GB/256 GB Flash storage) with 5GB stress testing.

    I reran the same test using a Mid 2013 MacBook Air (1.3 GHz/4GB/128GB Flash storage) . The Mid 2013 MacBook Air's CPU is faster than the 2011 MacBook Air. Apparently, it makes quite a big of difference for the Disk Speed Test. Below is the Disk Speed Test results with the 2013 MacBook Air.

    I also have a late 2012 Mac Mini (the dual core version). I haven't tried the R6 on it (don't feel like lugging the R6 to another room at the moment).

    I'm waiting for the upcoming Mac Pro to finally replace my old 2008 Mac Pro. I plan on using the R6 with the new Mac Pro.

    EDIT: See the following article regarding stripe size:

    http://www.tomshardware.com/reviews/RAID-SCALING-CHARTS,1735-4.html

    Question: what sort of read/write numbers does 4K editing require??
     

    Attached Files:

  9. cinemaloha, Sep 5, 2013
    Last edited: Sep 5, 2013

    cinemaloha macrumors newbie

    cinemaloha

    Joined:
    Sep 4, 2013
    Location:
    Online
    #9
    Is your R6 configured with RAID 5?
    Yes, it's RAID 5 configured.

    Please run the Disk Speed Test once you've configured your R6. I'm interested in how 1 MB stripe size does. Ideally, you'd want to run the test with 1MB stripe size and also with a smaller stripe size like 128KB or 256KB using the same hardware (4TB disks and same Mac). However, I don't know if you would want to re-create the logical drive for different stripe sizes since it takes a long time to synchronize the drives.
    Yes, will do. Once, my project slate is clean I will attempt the different Stripe Size and document my results and post screenshots.

    The previous test that I did was using a Mid 2011 MacBook Air (1.8GHz/4GB/256 GB Flash storage) with 5GB stress testing.

    I reran the same test using a Mid 2013 MacBook Air (1.3 GHz/4GB/128GB Flash storage) . The Mid 2013 MacBook Air's CPU is faster than the 2011 MacBook Air. Apparently, it makes quite a big of difference for the Disk Speed Test. Below is the Disk Speed Test results with the 2013 MacBook Air.
    Is it the 2013 MBA an i7 dual core? It's great to see the new test has improved speeds - I'm happy you tested it on another machine. This gives me more confidence in doing the 24 TB upgrade.

    I also have a late 2012 Mac Mini (the dual core version). I haven't tried the R6 on it (don't feel like lugging the R6 to another room at the moment).

    I'm waiting for the upcoming Mac Pro to finally replace my old 2008 Mac Pro. I plan on using the R6 with the new Mac Pro.
    Likewise, I will use the R6 with the new Mac Pro but I will wait until all the bugs are worked out so I will hold off until the second batch comes out. For my current projects and workflow, the Late-2012 iMac 3.4Ghz i7 has plenty of power. Plus, these projects will be completed early next year.

    EDIT: See the following article regarding stripe size:

    http://www.tomshardware.com/reviews/RAID-SCALING-CHARTS,1735-4.html
    Thanks for the link, I'll read up on Stripe Sizes.

    Question: what sort of read/write numbers does 4K editing require??[/QUOTE]
    When editing 4K, I can use "proxy" in FCPX so my current read/write speeds are sufficient. However, 4K requires larger storage space - approx. 35 MB per frame (@ 24 frames a second or more depending on project).
     
  10. randm thread starter macrumors newbie

    Joined:
    Jul 11, 2012
    #10
    Is it the 2013 MBA an i7 dual core? It's great to see the new test has improved speeds - I'm happy you tested it on another machine. This gives me more confidence in doing the 24 TB upgrade.

    It's the 1.3GHz Dual-Core 2013 MBA, which is slower than the 1.7GHz. So, I would expect that R6 disk speed test performance can be better on the faster MBA (and your iMac as well).
     
  11. dtpearson macrumors member

    Joined:
    Jul 26, 2010
    #11
    I just thought that i would report the successful use of Seagate 6TB drives (ST6000DX000) in a Promise Pegasus R6 in Raid5. These drives are NOT on Promises list of approved drives.

    Total usable size - 30TB

    I am getting about 700MB write and 820MB read, which is pretty damn good and probably getting near the limits of TB1

    It is still synchronising but I will retest once i get a bit of data into it (i have about 6TB to chuck in).

    I used 512KB stripe size with 4KB Sectors as i do mostly video and photo work with large file sizes.

    [​IMG][/url]R6 RAID5 6X6TB GRAPH 2 by dtpearson1975, on Flickr[/IMG]

    I had some issues when i had only 4 of the 6TB drives in the R6 with slow reads (only 250MB/sec) and janky writes with fast speed (500MB/sec) but it bounced up and down a lot. They worked fine in Raid0 (nice and fast) but not in Raid5. But all of these issues seem to have disappeared with six of the drives in Raid5.

    If i have any issues i will report back. I am keen to see what happens when i have lots of data in there.
     
  12. dia3olik macrumors member

    Joined:
    Sep 14, 2007
    #12
    Thanks for the update!
    Keep us posted about using these 6TB drives!

    BTW I'm using an R4 since may with 4x4TB Hitachi NAS (7200rpm) drives.

    All is good!!!
     
  13. 24frames24bits, Dec 20, 2014
    Last edited: Dec 22, 2014

    24frames24bits macrumors newbie

    Joined:
    Dec 20, 2014
    #13
    very interested in 6TB

    I currently have Pegasus 2 R6 with 2 TB/disk and would really like to use the 6 TB/disk model. One question I have, is can I change 1 drive at a time and not lose the data or do I need to change all 6 at once and then restore from another source? It looks like you can upgrade one disk at a time from the comments, understanding need all six the same for performance. They are expensive so wanted to be sure before buying them.

    Update: maybe obvious spoke with support and need to replace all drives at same time to get larger amount of storage. Still would like update on 6 TB model Seagate.
     

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