1. Do Not Buy a Hardware RAID Controller for Home Use

    November 17, 2010

    Hardware RAID controllers are considered 'the best' solution for high performance and high availability. However, this is not entirely true. Using a hardware RAID controller might even endanger your precious data.

    For enterprise environments, where performance is critical, it is more important that the arrays keeps on delivering data at a high speed. Professional RAID controllers use TLER with TLER-enabled disks to limit the time spend on recovering bad sectors. If a disk encounters a bad sector, there is no time to pause and try to fix it. The disk is just dropped out of the RAID array after just a couple of seconds. At that moment, the array still performes relatively well, but there is no redundancy. If another disk fails (another bad sector?) the array is lost, with all its data.

    More people are building NAS boxes for centralized storage of data, for private home use. Since disks are cheap, it is possible to create lots of storage capacity for little money. Creating backups of terabytes of data is however not cheap. Or you have to create two NAS boxes. But that is very expensive and not worth the effort.

    People seem to spend lots of money on expensive enterprise level hardware RAID cards, not understanding that the whole TLER-mechanism causes an increased risk for their data. In enterprise environments, budgets are relatively big, and data is always backed up. They can afford to take the risk of losing a RAID array due to these backups. But consumers often don't have the money to spend on creating backups of terabytes of data. They just go for RAID 5 or RAID 6 and hope for the best.

    For consumers, if the RAID array goes, all data is lost.

    So consumers should choose a RAID solution that will do its best to recover from hardware failure. Performance is not so much an issue. Reliability is. So consumers do want disks to spend 'ages' on recovering bad sectors if this means that the RAID array will survive.

    Linux software RAID and ZFS do not use TLER and therefore are a safer choice for your data then regular hardware RAID controllers. You may still use such controllers (but please test them properly) but only to provide SATA ports with individual disks, the RAID part should be handled by Linux.

    So in my opinion, hardware RAID controllers are more expensive, require more expensive (enterprise) disks and are less safe for your data.

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  2. Apple Is Killing Off the Optical Drive Just Like the Floppy Disk

    October 23, 2010

    With the release of the new MacBook Air we are one step closer to killing off the cd-rom and the dvd. As with the previous MacBook Air, this device has no optical drive. And that is a good thing. People do not need an optical drive. You have the network and you have USB disks. They are faster, more reliable and have more capacity.

    I may expect that in the upcoming years this trend may continue with the other laptops. Just as Apple killed the floppy disk, it is killing the optical drive, one step at a time. I'd rather have a smaller and lighter laptop or more disk or battery capacity, than an optical drive. So I hope this is a trend that will continue and all other manufacturers will follow.

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  3. Linux Software RAID Benchmarking Script

    September 29, 2010

    Just a small post.

    To benchmark your Linux software RAID array as setup with MDADM, please use my new benchmark script. I used this script to create these results.

    You may need to configure some values within the header of this file to make it fit your enviroment.

     DEVICES="/dev/sd[a-f]"
     NO_OF_DEVICES=6
     ARRAY=/dev/md5
     CHUNKS="4 8 16 32 64 128 256 512 1024"
     MOUNT=/storage
     LOG=/var/log/raid-test.log
     LOGDEBUG=/var/log/raid-test-debug.log
     LEVEL="0 5 6 10"
     TESTFILE=$MOUNT/test.bin
     TESTFILESIZE=10000 (IN MB, thus this is 10 GB)
     TRIES=5 (how many times to run a benchmark.)
    

    By default, the script wil format the array using XFS, feel free to format it with another filesystem such as EXT4 or EXT3 or whatever you want to test.

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