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  1. #1
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    Abnormal wear on SSD software raid 1

    We have a software raid 1 made with 2 x Samsung 840 Pro. The 2 SSDs were purchased from the same lot at the same time (about 6 months ago) and they were used together all the time.

    First SSD wear leveling count: 95%
    Second SSD wear leveling count: 75% (a week ago it was 77%)

    These values were taken from SMARTCTL.

    Is it normal for the wear of one SSD in a raid 1 array to be so different from the other?

  2. #2
    if you're running Linux make sure your log file is not grow, sometime you have Bad memory and report error log these files something grow. in the other hand if you run RAID1 make sure your controller PCI work property. another troubleshooting update Firmware from SSD always make backup!

  3. #3
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    In theory, the wear rate should be the same if they are identical drives in RAID1. Have there been any events where one of the drives fell out of RAID and needed to be resynced? For example, if drive 2 fell out, the RAID system would need to mirror the contents of drive 1 back into drive 2 when drive 2 came back in. If you had an event like that, then that would explain why drive 2 shows the wear leveling count much lower than drive 1.

    Also, the Samsung 840 Pro drives are fast but won't last nearly as long as an Intel S3700. The S3700 drives are more expensive initially, but they end up saving a lot of money over time since they last so much longer.
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  4. #4
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    Users on this forum have reported serious problems with the Samsung 840 Pro's in a RAID configuration. We ended up abandoning these drives earlier in the year after running into recurring performance problems.

    I highly recommend you read through this thread http://www.webhostingtalk.com/showthread.php?t=1223799 and in particular this post: http://www.webhostingtalk.com/showpo...&postcount=121

    Apparently there have been firmware updates that somewhat alleviate the problems, but I personally will never again install those drives in a RAID config.
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  5. #5
    Thanks for the topic!!! We were offered the same ssd's today, and I was planning to get them...

  6. #6
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    Quote Originally Posted by Cloudfastservers
    in the other hand if you run RAID1 make sure your controller PCI work property.
    I have looked for evidence in dmesg that the cable or port were malfunctioning but I found none.

    Quote Originally Posted by NoSupportLinuxHostin View Post
    In theory, the wear rate should be the same if they are identical drives in RAID1. Have there been any events where one of the drives fell out of RAID and needed to be resynced?
    There have been no such events that I know of. Also if there would have been such events the total number of LBAs written I believe should have been proportional to the wear but this is not the case. The number of the LBAs written for the "weared" are indeed larger but by 9-10% not by 500% like the wear.

    Quote Originally Posted by NoSupportLinuxHostin View Post
    Also, the Samsung 840 Pro drives are fast but won't last nearly as long as an Intel S3700. The S3700 drives are more expensive initially, but they end up saving a lot of money over time since they last so much longer.
    We don't have a budget for S3700. But we are considering S3500 for the next server.

    Quote Originally Posted by BrianHarrison View Post
    Users on this forum have reported serious problems with the Samsung 840 Pro's in a RAID configuration. We ended up abandoning these drives earlier in the year after running into recurring performance problems.

    I highly recommend you read through this thread http://www.webhostingtalk.com/showthread.php?t=1223799 and in particular this post: http://www.webhostingtalk.com/showpo...&postcount=121

    Apparently there have been firmware updates that somewhat alleviate the problems, but I personally will never again install those drives in a RAID config.
    I know of all those posts but I was under the impression that most (almost all) problems were fixed after the '05 firmware update. Unfortunately for me this was not the case. I did update the fw but it did nothing for us.


    Quote Originally Posted by Vex76 View Post
    Thanks for the topic!!! We were offered the same ssd's today, and I was planning to get them...
    Although I have blaimed Samsung and myself for choosing Samsung SSDs I think there's a chance for the Samsung SSDs not to be at fault here. If I write some large file to this array (hundreds of MB, or GBs) the whole server overloads to loads of 50 and even up to 100 and the copy speed fells down to less than 10MB/s. Now the asymetric wear rate that drops 2 points every week (so at least one will wear out in less than a year). I don't know if it's the Samsungs and I am not enough of a linuxist to find the answer alone. So it was not my intention to bash Samsung (although I am less than ok with my investment). And I believe that 840 Pro behind a hardware raid controller it's OK (provided they have the '05 firmware rev).

    I am just trying to find out if others have encountered similar issues:

    - asymmetrical wear rates for members of the same mirroring array
    - abysmal write speeds for larger files (less than 10MB/s)
    - extreme overloads when copying larger files
    - jbd2 jumps (after a large file written) to 100% I/O without doing any physical write or read
    - copying/writing a file will increase after a few seconds the %util (as indicated by IOSTAT) of the "weared" SSD for about 1 minute per GB.

  7. #7
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    Actually, the Intel S3700 has a much lower cost of ownership once you compare the P/E cycles. Over a period of 5 years, the S3700 drive is a lot cheaper. The S3700 is more expensive during the initial server build, but the S3700 drive lasts much longer. You would need to replace a Samsung 840 Pro quite a few times to handle the number of writes that a single S3700 can handle.
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  8. #8
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    Quote Originally Posted by BrianHarrison View Post
    Users on this forum have reported serious problems with the Samsung 840 Pro's in a RAID configuration. We ended up abandoning these drives earlier in the year after running into recurring performance problems.

    I highly recommend you read through this thread http://www.webhostingtalk.com/showthread.php?t=1223799 and in particular this post: http://www.webhostingtalk.com/showpo...&postcount=121

    Apparently there have been firmware updates that somewhat alleviate the problems, but I personally will never again install those drives in a RAID config.
    By the way...what kind of raid setup have you had problems with, regarding the 840 Pro's? Hardware or Linux raid (mdraid)?

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