> From: Amir Goldstein <amir73il@xxxxxxxxx> > Date: Monday, September 12, 2022 at 9:38 AM > To: Jan Kara <jack@xxxxxxx> > Cc: linux-fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>, Miklos Szeredi <miklos@xxxxxxxxxx> > Subject: Re: thoughts about fanotify and HSM > > On Mon, Sep 12, 2022 at 3:57 PM Jan Kara <jack@xxxxxxx> wrote: > > > > Hi Amir! > > > > On Sun 11-09-22 21:12:06, Amir Goldstein wrote: > > > I wanted to consult with you about preliminary design thoughts > > > for implementing a hierarchical storage manager (HSM) > > > with fanotify. > > > > > > I have been in contact with some developers in the past > > > who were interested in using fanotify to implement HSM > > > (to replace old DMAPI implementation). > > > > Ah, DMAPI. Shiver. Bad memories of carrying that hacky code in SUSE kernels > > ;) > > > > So how serious are these guys about HSM and investing into it? Because > > Let's put it this way. > They had to find a replacement for DMAPI so that they could stop > carrying DMAPI patches, so pretty serious. > They had to do it one way or the other. > > They approached me around the time that FAN_MARK_FILESYSTEM > was merged, so I explained them how to implement HSM using > FAN_MARK_FILESYSTEM+FAN_OPEN_PERM > Whether they ended up using it or not - I don't know. > On Tue, Sep 13, 2022 at 2:01 AM Plaster, Robert <rplaster@xxxxxxxxxxxxxxxxxxxx> wrote: > > Hi Amir – Dan got back to me. He said (fyi - SMS referenced below is our HSM app): > Hi Rob, I will add that from what I read on your website [1], your entire product is open source, code is available on your web servers as rpms and will be put up on GitHub soon. That's very good news, because it means I will be able to demo my proposed fanotify interface improvements on your code base :) [1] https://deepspacestorage.com/resources/#downloads > > > “Amir talks about specific fanotify events used for an HSM. He says FAN_MARK_FILESYSTEM+FAN_OPEN_PERM should be enough for a basic HSM. As it is currently implemented, SMS uses FAN_MARK_ADD+FAN_OPEN_PERM to detect purged files and FAN_MARK_ADD+FAN_CLOSE_WRITE events to determine when a file has been potentially modified. There are other FANOTIFY events that would be useful, but we're currently limited by the older Linux kernels in the RHEL releases we're supporting. > > > > If I understand what Amil is proposing, it appears to be some new FANOTIFY FAN_PRE_* events. Some of it looks like something we would be interested in but as long as we continue to support older RHEL kernels, we're very limited to what we have to work with.” > My goal is to design the interfaces for the use of future more advanced HSM clients. The experience that you can bring to the table from customers using your current HSM client is very important for making design choices for future HSM clients - i.e. understand and address the pain points with current fanotify interface. So as long as this is "something that you would be interested in" I know I am in the right direction ;-) Thanks, Amir.
