External USB hard drive - Hardware

This is a discussion on External USB hard drive - Hardware ; I wonder if people who have used such hardware under Linux could contribute their experiences? I am interested in performance and reliability, mostly, but also on setup simplicity. In particular, would using such a hard drive be an appropriate medium ...

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Thread: External USB hard drive

  1. External USB hard drive

    I wonder if people who have used such hardware under Linux could
    contribute their experiences? I am interested in performance and
    reliability, mostly, but also on setup simplicity. In particular, would
    using such a hard drive be an appropriate medium for backups? I would be
    interested for the drive to be active only when the backup is being
    performed; I understand that these drives can be configured so that they
    stop spinning after they have not been accessed for some time.




  2. Re: External USB hard drive

    Harold Weissman writes:
    > I wonder if people who have used such hardware under Linux could
    >contribute their experiences? I am interested in performance


    The transfer rate is limited to about 30MB/s (if you get a fast
    USB/IDE interface, there are also slower ones around), otherwise the
    performance is the same as for internal drives.

    >reliability,


    No problems in my experience.

    > mostly, but also on setup simplicity.


    They are very simple to set up. Plug them in, turn them on, mount
    them (or you can automount them through hotplug or on-demand). Oh,
    partition and format them the first time.

    > In particular, would
    >using such a hard drive be an appropriate medium for backups?


    Yes. I am using them for this purpose.

    > I would be
    >interested for the drive to be active only when the backup is being
    >performed; I understand that these drives can be configured so that they
    >stop spinning after they have not been accessed for some time.


    IDE drives can be configured to do that, but IME they are configured
    by default not to spin down, and you cannot tell them to spin down
    with "hdparm -S ..." through the USB interface.

    However, if you want to use them as a backup medium, I would recommend
    to remove them anyway while not backing up, for several reasons:

    - You should store the backups as far away from the main storage as
    practical, for increase safety against localized disasters (e.g.,
    fire, theft).

    - You don't want all the backup disks to be on-line when a cracker
    breaks in and trashes all the hard disks he can reach.

    - anton
    --
    M. Anton Ertl Some things have to be seen to be believed
    anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
    http://www.complang.tuwien.ac.at/anton/home.html

  3. Re: External USB hard drive

    Harold Weissman wrote:
    > I wonder if people who have used such hardware under Linux could
    > contribute their experiences? I am interested in performance and


    I have recently acquired a Western Digital MyBook 250GB and the
    performance is very good on a USB2 interface.

    > reliability, mostly, but also on setup simplicity.


    I haven't had a chance to test the reliability as it's still new, but
    setup was simply a case of plugging it in and Mepis automounted it.

    > In particular, would
    > using such a hard drive be an appropriate medium for backups?


    That's what I'm using mine for.

    > I would be
    > interested for the drive to be active only when the backup is being
    > performed; I understand that these drives can be configured so that they
    > stop spinning after they have not been accessed for some time.


    The MyBook automatically spins down after a certain amount of inactivity
    and will switch itself 'off' when unmounted.


  4. Re: External USB hard drive

    Harold Weissman wrote:

    > In particular, would
    > using such a hard drive be an appropriate medium for backups?


    Hello Harold,

    In addition to the other replies, I would like to recommend you the tool
    named "StoreBackup". This utility does make daily backups of selected
    folders to a ext3 (or similar, but not FAT or NTFS) partition. Instead of
    copying the whole lot of files and eating up your disk space in no time, it
    uses hard links for unchanged files and actually copies only the
    new/changed ones. Thus, you have available complete daily snapshots of your
    data, by simply using any file browser.

    StoreBackup Homepage: http://sourceforge.net/projects/storebackup
    Tutorial specific to SuSE: http://en.opensuse.org/StoreBackup

    With regards,
    Hendric
    --
    > Hendric Stattmann, Mödling, Austria. Registered Linux User #178879



  5. Re: External USB hard drive

    In article <2007Jul30.205026@mips.complang.tuwien.ac.at>,
    Anton Ertl wrote:
    >Harold Weissman writes:
    >> I would be
    >>interested for the drive to be active only when the backup is being
    >>performed; I understand that these drives can be configured so that they
    >>stop spinning after they have not been accessed for some time.

    >
    >IDE drives can be configured to do that, but IME they are configured
    >by default not to spin down, and you cannot tell them to spin down
    >with "hdparm -S ..." through the USB interface.


    sg3_utils includes a command, sg_start, that'll manually spin down USB hard
    drives. If you wrap it in a shell script that runs every few minutes as a
    cron job, it'll spin down your drive when it's not in use:

    #!/bin/sh

    # needs sg3_utils 1.23 or later

    source /etc/profile

    if [ \! "`fuser -c /mnt/music 2>/dev/null`" ]
    then
    sg_start --stop /dev/disk/by-label/music
    fi

    if [ \! "`fuser -c /mnt/video 2>/dev/null`" ]
    then
    sg_start --stop /dev/disk/by-label/video0
    fi

    This particular script spins down the two drives hanging off my MythTV box
    for music & movie storage. For each drive, it first checks the mount point
    for open files on the drive. If there are no open files, the drive is told
    to spin down. Any activity on the drive that can't be handled by the cache
    will cause the drive to spin back up. I have this script set to run every
    10 minutes.

    _/_
    / v \ Scott Alfter (remove the obvious to send mail)
    (IIGS( http://alfter.us/ Top-posting!
    \_^_/ rm -rf /bin/laden >What's the most annoying thing on Usenet?


  6. Re: External USB hard drive

    Hendric Stattmann wrote:

    > Harold Weissman wrote:
    >
    >> In particular, would
    >> using such a hard drive be an appropriate medium for backups?

    >
    > Hello Harold,
    >
    > In addition to the other replies, I would like to recommend you the tool
    > named "StoreBackup". This utility does make daily backups of selected
    > folders to a ext3 (or similar, but not FAT or NTFS) partition. Instead of
    > copying the whole lot of files and eating up your disk space in no time,
    > it uses hard links for unchanged files and actually copies only the
    > new/changed ones. Thus, you have available complete daily snapshots of
    > your data, by simply using any file browser.


    Hmmm...

    Hard links won't work across filesystems so you cannot put your backups on
    another hard disk.

    What happens if your disk (or filesystem becomes corrupted? You lose both
    your data and your backup.

    I use lvm-snapshots and rsync to update my systems onto a separate and
    external HDD.

    Sorry, didn't look at your link. Maybe there's a way to get around the above
    problem.

    --
    Regards,

    Gregory.
    Gentoo Linux - Penguin Power

  7. Re: External USB hard drive

    On Mon, 30 Jul 2007 15:58:54 +0000, Harold Weissman wrote:

    > I wonder if people who have used such hardware under Linux could
    > contribute their experiences? I am interested in performance and
    > reliability, mostly, but also on setup simplicity. In particular, would
    > using such a hard drive be an appropriate medium for backups? I would be
    > interested for the drive to be active only when the backup is being
    > performed; I understand that these drives can be configured so that they
    > stop spinning after they have not been accessed for some time.


    I've used a USB external for backing up partitions on my laptop when I
    swapped out the 40gb drive for a 120. Also restored after. Works fine.
    Firewire will give you faster speeds.


  8. Re: External USB hard drive

    Gregory Shearman wrote:

    > Hard links won't work across filesystems so you cannot put your backups on
    > another hard disk.


    Hi Greg,

    The links are not put between the backup HD and the original files, but only
    between files on the backup HD, in order to save space and still make
    differential backups look like full backups to the user.

    Hendric
    --
    Hendric Stattmann, Mödling, Austria. Registered Linux User #178879

  9. Re: External USB hard drive

    Hendric Stattmann wrote:

    > Gregory Shearman wrote:
    >
    >> Hard links won't work across filesystems so you cannot put your backups
    >> on another hard disk.

    >
    > Hi Greg,
    >
    > The links are not put between the backup HD and the original files, but
    > only between files on the backup HD, in order to save space and still make
    > differential backups look like full backups to the user.


    Ah, it all makes sense now.

    --
    Regards,

    Gregory.
    Gentoo Linux - Penguin Power

  10. Re: External USB hard drive

    Harold Weissman wrote:
    > I wonder if people who have used such hardware under Linux could
    > contribute their experiences? I am interested in performance and
    > reliability, mostly, but also on setup simplicity.


    Performance is good enough.

    Reliability can vary. I've run into numerous problems with the
    Maxtor external drives. With Maxtor's external USB enclosures , the
    drive would overheat the on-board controller and cause the whole
    device to drop off the USB bus. The only way to get it back would
    be to power cycle the external drive. I got tired of dealing with
    this one or more times a week so I wound up pulling the drive out of
    Maxtor's external enclosure and just mounting it in the server.
    I've also seen this problem with other vendor's external enclosures.
    I don't really know of good enclosure to recommend, but I would
    suggest that you get one that has plenty of cooling capacity in it
    (i.e., fans). I'd avoid any of the enclosures that rely on passive
    cooling alone to deal with heat transfer.

    Assuming your distribution/kernel are configured for USB storage,
    using these devices is pretty simple. Typically plug them into the
    USB bus, wait for them to be detected, and then mount using whatever
    the device (e.g., /dev/sda1) the drive was detected as. If you're
    going to use more than one of these devices, you can run into issues
    where one device might be detected as /dev/sda sometimes and maybe
    /dev/sdb others. Use labels on your filesystem(s) and then use the
    LABEL= syntax within /etc/fstab. With labels, you don't have to worry
    about what order the devices get detected and what device name they
    get assigned.


    > In particular, would using such a hard drive be an appropriate medium
    > for backups?


    Assuming you get reliable hardware, it works well. I like to use
    rsync for the stuff I do.

    > I would be interested for the drive to be active only when the backup
    > is being performed; I understand that these drives can be configured
    > so that they stop spinning after they have not been accessed for some
    > time.


    Some of these enclosures are "smart", in that they'll spin the drive
    down if they detect it hasn't been active in awhile. You can help
    facilitate that by only mounting the drive when you're going to do
    the back-up. For the backup scripts I've written, I start off by
    mounting the drive/filesystem, do an rsync backup, and then umount
    the filesystem. This insures there's not going to be any activity
    against the filesystem and thus will allow the drive to spin down.
    If the enclosure itself doesn't have this feature, there's other
    ways to spin the drive down, as others have all ready replied.


    --

    If you want to reply via email, change the obvious words to numbers and
    remove ".invalid".

  11. Re: External USB hard drive

    In article ,
    Scott Alfter wrote:
    > In article <2007Jul30.205026@mips.complang.tuwien.ac.at>,
    > Anton Ertl wrote:
    > >Harold Weissman writes:
    > >> I would be
    > >>interested for the drive to be active only when the backup is being
    > >>performed; I understand that these drives can be configured so that they
    > >>stop spinning after they have not been accessed for some time.

    > >
    > >IDE drives can be configured to do that, but IME they are configured
    > >by default not to spin down, and you cannot tell them to spin down
    > >with "hdparm -S ..." through the USB interface.

    >
    > sg3_utils includes a command, sg_start, that'll manually spin down USB hard
    > drives. If you wrap it in a shell script that runs every few minutes as a
    > cron job, it'll spin down your drive when it's not in use:
    >
    > #!/bin/sh
    >
    > # needs sg3_utils 1.23 or later
    >
    > source /etc/profile
    >
    > if [ \! "`fuser -c /mnt/music 2>/dev/null`" ]
    > then
    > sg_start --stop /dev/disk/by-label/music
    > fi
    >
    > if [ \! "`fuser -c /mnt/video 2>/dev/null`" ]
    > then
    > sg_start --stop /dev/disk/by-label/video0
    > fi


    Since you have the same code there twice, I would try to eliminate
    duplication as much as possible by using a loop:

    #!/bin/sh

    # needs sg3_utils 1.23 or later

    source /etc/profile

    for drive in music video ; do
    if [ \! "`fuser -c /mnt/$drive 2>/dev/null`" ] then
    sg_start --stop /dev/disk/by-label/$drive
    fi
    done

    Fewer things to debug that way.

    --
    -eben QebWenE01R@vTerYizUonI.nOetP royalty.mine.nu:81

    And we never failed to fail / It was the easiest thing to do -- CSN


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