Issue_discards In Lvm.conf

Home » CentOS » Issue_discards In Lvm.conf
CentOS 10 Comments

I decided that the next time I reformatted my main desktop computer (this one) I would have a ssd installed in it to use for the boot drive. Now that CentOS 7 is on the horizon, I’m thinking that the time is approaching when I’ll want to do that.

The last time I set up a computer with a ssd in it, that was the only drive that it had. I changed issue_discards=0 to issue_discards=1 into the /etc/lvm/lvm.conf file, set up cron to run fstrim on that drive on a weekly basis, and that was it.

Since this next setup will have both a ssd and a regular hard drive in it, is there some way that I should specify that issue_discards=1 applies only to the ssd or does that matter? I see that the explanation in the lvm.conf file says “If set to 1, discards will only be issued if both the storage and kernel provide support.” so I’m left with the impression that the issue_discards setting won’t affect a regular hard drive even if it is set to 1.

10 thoughts on - Issue_discards In Lvm.conf

  • I have a question about SSD respecting security. Recently I have been investigating sanitizing these devices, together with ‘smart-phones, tablets and pads which use flash memory persistent storage. Not to mention the ubiquitous USB ‘memory stick’. I have come to the rather unsettling conclusion that it is effectively impossible to ‘sanitize’ these things short of complete and utter physical destruction, preferably by incineration. Is this in fact the case?

  • * Hopefully someone who is more of an expert on this matter will speak up.

    I’ve come to the same conclusion. Due to controller wear leveling and TRIM, it is difficult to fully sanitize a flash memory (USB flash, SSD).

    A former employer of mine contracts out destruction of conventional hard drives with a machine that has a hydraulic arm and a wedge. Effectively bending the platters and some of the drive. Hardware destruction (prior to recycling/disposal) in certain business sectors is common place.

  • my employer uses a service that shows up monthly and has a metal chipper in the back of their truck. disks go in and are fully ground up into metal chips, under the supervision of our security people.

  • SilverTip257 wrote:

    mention the incineration.

    Where I work, some of the systems (which are behind an *internal*
    firewall) have PII and HIPAA data – we’re serious about protecting that stuff. When we surplus a server, the drive must be certified to be sanitized – that is, for the ones I do, which is most of them, I need to sign my name to a form that gets stuck on the outside that it’s sanitized, making me *personally* responsible for that.

    We use two methods: for the drives that are totally dead, or *sigh* the SCSI drives, they get deGaussed. For SATA that’s still running, we use DBAN. *Great* software. From what I’ve read, one pass would probably be good enough, given how data’s written these days. With my name certifying it, I do paranoid, and tell DBAN the full 7-pass, DoD 5220.22-M. I
    *really* don’t think anyone’s getting anything off that.

    We don’t have any SSDs, so I can’t speak to that. Bet you could deGauss them, easily enough. Or maybe stick ’em on a burner on a stove to get over the Curie point….*

    mark

    * Techniques that a techie group I belong to refer to as “things to do in someone else’s kitchen”

  • if the drive has remapped tracks, there’s stale data on there you can’t erase with DBAN.

    degaussing would do nothing to flash memory, its semiconductor, not magnetic.

  • –I would concur with that assessment. Similar to what others have mentioned, with spinning platters I use either DBAN for relatively insensitive disks and physical destruction for sensitive stuff
    (preferably after DBAN, if it is still a working disk). When it comes to SSD and other memory-based technologies, physical destruction only.

    A couple of weeks ago I was buying some consumer-grade disks for a particular project. The sales guy was of course trying to up-sell me on their in-store replacement plan. I tried to explain to him that even if I thought such plans were actually worth something, it would be pointless because I *never* RMA a hard drive.

    I think he was dense; he didn’t seem to grasp the concept.

    Devin

  • I worked in the SSD lab at STEC for a while, testing SSD’s and fixing SSD’s that failed…

    When I was working in the lab on the Zuess drives (First enterprise class SSD drive) . When the drives came back from our customers hosed, all we had to do was re-flash the firmware (helps if you have the software and the firmware to reflash the drives, the hardware was your basic server). I don’t know about you problem, or which manufacturing process drives you are using…but the Zeuss drives only needed a firmware reflash.

    This was just a 2u server with a software program that would allow me to reflash the drives.

    There were 2 kinds of SSD drives (2 manufacturing processes). The consumer grade which had a MTF of 2 years, and/or X writes. There was the other process, enterprise class drives which had a MTF of ~ (yes infinity) theory was they would never fail.

    I knew how to blow up the drives, run them well beyond the capacity of spinner drives. But then I would flash the firmware and the drive would be good as new. I would be running about 200 music videos at the same time to get enough throughput to cause it to crash. The goal was to find
    *when* they blew up, so we could limit them in firmware before then.

    We all know manufacturers know how to make benchmarks lie. They told me which tests to run to make our drives blow away the spinners, and which ones not to do. The very fragmented drives RO, SSD blew away the spinners, but Writting sequentially (both blank drives to start) there was little difference.

    When our customers (the major SAN manufacturers) returned the drives. There was one of two things wrong with them…
    1. They got a drive with a bad firmware version. Reflash and it is fixed.
    2. Their design was good enough for spinner drives but did not follow the standard for [SAS|FIBER] and we found the problem, advised them what it was so they could change thier design.

    I remember when I dropped a $40k sample…lab manager looked at me…stared at me…then burst out laughing. The enterprise SSD’s were nearly indestructible and when someone dropped on for the first time, they would *try* to look angry, but then would burst into laughter at the nervous engineer.

    If I got any details slightly off, hey it was a decade ago! :)

  • Dan Hyatt wrote:

    Interesting. But did you ever stick one in a microwave? (Someone else’s, that is ) Or aim an oxy-acetylene torch at it, he asks, innocently? I
    don’t have an EMP gun handy….

    Oh, the ones that aggravate me are the ones who limit what you can do, like WD, then the others, who changed the firmware starting in ’09, so that you *couldn’t* change the TLER from 2 min to 7 sec….

    mark