> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Bob Friesenhahn > > Unfortunately, if dedup was previously enabled, the damage was already > done since dedup is baked into your pool. The situation may improve > over time as dedup blocks are gradually eliminated but this depends on > how often the data gets overwritten and how many old snapshots are > deleted.
No matter how you cut it, unless you want to "zpool destroy," there is a fixed total amount of time that will be spent destroying zfs snapshots that have previously dedup data baked into them. Your only choice is when to perform that work, and broken into what granularity. Most likely you're talking about daily snapshots at this point. Where each night at midnight, some time will be spent destroying the oldest daily snapshot. Most likely the best thing for you to do is simply to do nothing, and allow 2 hours every night at midnight, until those old snaps are all gone. But if you wanted, you could destroy more snapshots each night, and get it all over with sooner. Or something like that. > The alternative is to install a lot more RAM, or install a SSD as a > L2ARC device. RAM (ARC) and SSD (L2ARC) are only going to help prevent re-reading the blocks from disk after they've been read once. No matter what, if you're talking about time to destroy snapshots, you're going to have to spend time reading (and erasing) those blocks from disk. So infinite ram and infinite SSD aren't going to help you at this point. Given that it's already been created with dedup, and the DDT is not currently this instant already in cache. I mean... Yes, it's marginally possible to imagine some benefit, if you install enough ram or cache, you could read all the contents of the snapshot during the day so it will still be warm in cache at night when the snap gets destroyed, or something like that. Maybe able to spread the workload out across less critical hours of the day. But like I said. "Marginal." I doubt it. Most likely the best thing for you to do is simply do nothing, and wait for it to go away in the upcoming weeks, a little bit each night. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
