Update: tcsh too.
If you’ve ever wondered about how you can resize/move a HAMMER filesystem, follow this thread for a variety of answers.
Matthew Dillon has written up another update on his progress with HAMMER2. (I need to be consistent in how I write that.) He has disks being exported and mounted on other systems, and adds an explanation of some of the issues around creating reliable multi-master setups. Before you get too excited, no, multi-master isn’t working yet, and this is not production ready.
Matthew Dillon’s put more of his Hammer work into DragonFly, with notable parts being the creation of a ‘dmsg’ setup for advertising available block devices to share between machines using Hammer. To anticipate your next question: No, it’s not something you can run right now as a test; this is the underlying framework.
The weather is finally turning cooler, which makes me happy.
- I don’t think I’ve seen this before: Very old UNIX releases, listed for running in emulation. (via)
- Where the red-black tree name came from. A red-black tree underpins Hammer 1′s data structures, though it does not in Hammer 2. (also via)
- Someone with a HP passport login want to help this guy? He just needs to reinstall Windows in IDE mode, or perhaps find the right sysctl to toggle.
- The acme editor, from Plan 9. I didn’t realize it’s 20 years old.
- Speaking of editors, Replace in Multiple Files with Vim. I haven’t seen the argdo command before, or the Vim Ninjas site. Their color schemes article is useful just for the screenshots. (via)
- Adbuntu. It’s not as bad or as inconsequential as most reactions would lead you to believe, but advertising within an OS seems heavy-handed. The BSD model has been to use the operating system as a vehicle for selling hardware, and that’s been much more successful. (see iOS, PC-BSD.)
- Where Did the Internet Come From?
- The map for Adventure. (via)
Your unrelated link of the day: Victorian Sci-Fi. It’s not just a reference list, it’s a link to a lot of the original material, since copyright no longer applies.
If you do, they don’t get cleaned up during the normal ‘hammer cleanup’ nightly routine. Chris Turner has added a way to manually specify them as a cleanup target.
I’m pretty sure in this case ‘offline’ means ‘nothing streaming to it from a master disk’. I think.
These are small, but they make life easier: Hammer now has a scoreboard file, for viewing of mirror-streams running in the background. There’s also a ssh-remote directive, so you can use ssh without enabling an interactive shell, and a HAMMER_RSH environment variable so different remote shells can be used. These are all for Hammer 1.
There’s certainly no theme to this week’s links. I even manage to avoid my usual git and vim links, strangely.
- Ethernet’s Future: How Fast Is Fast Enough? The article doesn’t answer any questions, but I like the IEEE-supplied graph it opens with that shows the trend of overall network traffic doubling yearly. (via)
- Anti-open source propaganda in Disney kids’ TV show. I’m actually more bothered by trying to hyphenate a phrase made from separate words. Anti-’open source’? Esoteric grammar issues appeal to me.
- Bash One-liners Explained, part 3.
- Perl hex and bit pack formats were added to fix the Magellan satellite’s output. A neat origin for something I’ve used trivally. Of course, I suppose any use is trivial compared to fixing output from a broken spaceship. (via many places)
- Here’s a DragonFlyBSD article from 2010 linked on Hacker News. The ensuing conversation in the Hacker News comments is lucid and useful, and not a single bit of whining about BSD being dead. That’s so refreshing to see!
- Looks like there will be a new version of ADOM. Will it run on DragonFly? It should, since the previous version is in pkgsrc.
- Do you like set theory? Then read this. I don’t understand a word of it, but I like seeing the mathematical characters encoded on the page, apparently using MathJax.
- I also enjoy reading about BSD users’ origin stories. In this case, Dru Lavigne.
- CDE has been open-sourced. There’s a good chance it will show up in pkgsrc soon. Seeing this interface will make you nostalgic if you are the right age.
- If you’re a fan of the Hammer filesystem, does that make you a hammerhead? That’s my weak attempt to segue to this comic.
- Artisanal, hand-crafted unsigned ints. Read the bottom of the About page for an explanation. This may not make sense to you if you haven’t encountered the trend it’s making fun of, which seems to be centered in Brooklyn. (via)
- I hope you enjoy scrolling, because this history of computers and history of computer graphics are very long single documents. I like seeing the early computer art. (via)
Your unrelated comic link of the week: Cul De Sac. The strip is ending due to the creator’s health issues, but what he has done is marvelous. This is one of the few newspaper strips that is both visually interesting and often abruptly laugh out loud funny, without being patronizing.
If you wanted to try Hammer 2 and you have several DragonFly-current systems around (virtual or not), Matthew Dillon has the instructions. Keep in mind that this is not something ready for use; it can’t actually free up space, for instance. It’s neat that you can have multiple systems passing data back and forth already, though!
Matthew Dillon recent posted a status report for Hammer 2. Of interest is the spanning tree protocol being built to handle messages between Hammer volumes. As he says in the message:
For example, we want to be able to have millions of diskless or cache-only clients be able to connect into a cluster and have it actually work…
(No, it doesn’t do this, yet.)
Hammer 2 (or is it HAMMER2?) is nowhere near ready to test. But! For laughs, I think it could be set up just so you can watch the messages go back and forth. Someone want to set up a few DragonFly-current VMs and try?
Reading this HAMMER2 commit carefully shows some future plans: remote cluster control, and the ability to mount nonlocal HAMMER2 volumes. A reminder: those are future plans, not what you can do now.
As noted in a recent commit, it’s possible to set up a HAMMER2 /usr/obj and survive a buildworld. That’s good progress.
Note that this is basic work, so features like multi-master and deduplication are not present yet, and it’s still work in progress, so don’t try HAMMER2 unless you like losing data. Watch the branch for changes, though.
(I’m going with “HAMMER2″ for the name.)
If you’re curious about Hammer2 development, it’s been ongoing, but there haven’t been any more juicy commits to point at. Here’s one – the start of the messaging system.
Here’s an interesting side effect that came up in Hammer 2 development: deleting files can potentially require modification of only one parent element. If I’m reading it right, that means deletion always takes about the same time, independent of the amount of data being deleted. Your ‘rm -rf /largedrive’ could complete, removing multiple terabytes of data before you realize it. I suppose it’s silly to complain about speedy results. Of course, being Hammer, it would still be available in history.
There’s a Hammer 2 branch in the DragonFly git repo now, for the next generation of DragonFly’s native file system. Don’t get too excited; as Matthew Dillon explains, it won’t be operational for months, and features won’t get added until much later this year. It’s neat to see the work happening, though, and there’s a new design document to show what’s coming.
Matthew Dillon has a very detailed commit message with changes to make sure Hammer will run overnight cleanups in situations as low as 256M of RAM. I think you can find that much RAM in breakfast cereal boxes these days.
If you’re running DragonFly on a very low-end system, you may be wondering about memory requirements for Hammer. Hammer is much less RAM-hungry than ZFS, so it looks like you can get away with 128M, as long as you don’t mind the occasional error message. You can manually tweak settings for it if you like. 256M is plenty.
It still strikes me as odd to consider systems with less than 1G of RAM as “low-memory”. What rich times we live in!
Antonio Huete Jimenez’s ‘libhammer‘, a library to make various Hammer functions available to userland programs, has been added. It implements ‘hammer info’ only at this point, if I understand correctly.
Francois Tigeot took an old Summer of Code proposal, VFS Quotas, and started running with it. He’s made some progress, as he detailed in a recent post to kernel@ (with code!) , but the nullfs-mount nature of PFSs in Hammer are making it difficult.
Well, if you tell it to do so. Matthew Dillon has added a user-settable limit to the amount of memory used during deduplication, so if your Hammer-using system is low on RAM, you can conserve. This is probably most useful if you are running DragonFly in an extremely small VM, or if your name is Venkatesh.
(inside joke; Venkatesh has a crazy old desktop for DragonFly.)
I really just like that phrase and the action movie feeling of using it, like “Watch out! The pulse-width modulated time-domain multiplexer is targeting us!“ Sorta like a PU-36 space modulator. It’s actually a recently-committed mechanism to improve write performance in Hammer, but my idea sounds more exciting.
I’ve posted about my own results with Hammer deduplication here before, but Siju George put together results from his workplace using actual files in production. He recovered 138G from a 1T disk, and recovered 20% of space from another disk. Not bad for something that’s nearly automatic, and completely free.
I moved to DragonFly 2.10 over the past few days, and I tried out deduplication, to see what kind of results I would get. The procedure is outlined below. I’m using /home here as an example, just to reduce the amount of text pasted in.
/pfs/@@-1:00004 966000640 566434576 399566064 59% /home
Move my various Hammer pseudo-file systems to version 5, which supports deduplication.
# hammer version-upgrade /home 5
Issue a deduplication simulate command, to see what it guesses will be the savings:
# hammer dedup-simulate /home
Dedup-simulate /home: objspace 8000000000000000:0000 7fffffffffffffff:ffff pfs_id 4
Dedup-simulate /home succeeded
Simulated dedup ratio = 1.22
That ratio turned out to be pretty accurate for the actual deduplication. I didn’t time it, unfortunately. I don’t know if the time taken is proportional to the amount of deduplication or the total volume of data, though I suspect the latter.
# hammer dedup /home
Dedup /home: objspace 8000000000000000:0000 7fffffffffffffff:ffff pfs_id 4
Dedup /home succeeded
Dedup ratio = 1.22
462 GB referenced
378 GB allocated
14 MB skipped
6869 CRC collisions
0 SHA collisions
0 bigblock underflows
The end result?
/pfs/@@-1:00004 966000640 505887504 460113136 52% /home
That data space is shared across all file systems, and it’s a 1TB disk, so it’s 7%, or 70GB. I was hoping for more, but I don’t have any obviously duplicated data (no local mail store, no on-disk backups), so perhaps this is normal. 70GB that I didn’t have before is no bad thing, though.
Incidentally, I was able to upgrade my installed software from pkgsrc-2009Q4 to pkgsrc-2011Q1 entirely using pkg_radd -u <pkgname>. Remarkably quick and painless, though pkgin may have been able to do it even faster since it would pull from the same place.
If you follow this thread, it has some discussion on how to handle a multi-disk setup and Hammer. If a disk is going bad, you can try mirroring, though you have to be careful how your pseudo-file systems are set up.
I didn’t think of this, but I needed it: if you have an older Hammer system that now can perform deduplication because you upgraded to DragonFly 2.10, make sure to add it to the configuration for that file system, or else it won’t run.
Matthew Dillon’s been thinking about Hammer, and how to implement clustering well enough to work as a sort of RAID replacement. He’s written up a document describing his plans. Some highlights:
- writable history snapshots
- quotas and accounting
- live rebuilds of data from mirrors
- and the same history, mirroring, and snapshots as before.
It’s going to be a while before this “Hammer 2″ becomes a finished product, though, so don’t count on it for the next release.
Tomas Bodzar asked about RAM usage with Hammer and deduplication, pointing at this example that shows ZFS requiring… I’m not sure. Lots? Anyway, Matthew Dillon noted that offline deduplication in Hammer would use available RAM/swap for CRCs on all files, but only a limited subset for ‘live’ dedup. For a real-world example, Venkatesh Srinivas described deduplicating about 600G down to 400G, with a machine having only 256M of RAM. Yes, only 256M.
Enabling the vfs.hammer.double_buffer=1 sysctl will greatly improve Hammer performance when you’ve exceeded your memory cache (at a possible slight penalty when you have not) and also speed things up when using live deduplication.
Update: Venkatesh Srinivas says:
“double_buffer makes sense when: 1) you want all CRCs to be checked on reads. 2) you’re running live dedup and care about dedup performance rather than say read-heavy performance; 3) you have swapcache but are often running into the vnode limit in what you can cache.”
So, not always useful.
The default Hammer version in DragonFly is now version 5, which is the one that includes deduplication. Enjoy, bleeding-edge users! Otherwise, wait for the next release.
Version 6 is there, but don’t upgrade to it yet; there aren’t significant user-visible changes, and the usual disclaimers for new versions apply.
A Phoronix test of DragonFly’s Hammer filesystem turned up, via Siju George. It’s not really a benchmark as much as it is a speed test, and it’s not a realistic comparison, but it’s interesting to see numbers.
They need a graph that shows how much historical data can be recovered by each file system, or how long fsck takes after a crash.
Update: Matthew Dillon points out the many ways these tests are wrong.
Ilya Dryomov’s work on deduplication for Hammer has been committed to the tree in an early test form. I guess I need to pay up as part of the code bounty. If you’re wondering how much space it will save, but don’t want to try non-production code yet, there’s a ‘hammer dedup-simulate’ command that will estimate the saving ratio.
This is great news – deduplication is so valuable it adds an extra zero onto the price of any storage device that can do it.
A smaller set of links, but still the same volume of reading material.
- Samuel Greear linked to this lengthy writeup on how to have both the consistency of ACID and the scaling of NoSQL. Astute observers may notice the similarities between the plan described and the way HAMMER works.
- Joerg Sonnenberger pointed out to me, after my works on The BSD Show! that MOSIX is an open source single-system-image implementation, though it appears to be designed for specialized high-speed networks rather than the more general case of DragonFly.
- This seems bizarre. (via)
Matthew Dillon posted a summary of recent bugfixes in HAMMER and kqueue, which means if you are running a version of bleeding edge DragonFly build in the last few weeks, you should update.
He also mentions a “significant improvement in performance” in disk encryption. How significant? Over three times as fast.
Matthew Dillon reports that DragonFly now has a catastrophic recovery tool for HAMMER filesystems, with pertinent details.
Matthew Dillon has provided some details about recent kernel work, along with a release forecast.
You have probably seen reports declaring the demise of OpenSolaris by now, many taking a less than conservative approach in reporting the news one way or the other. So what do you make of the news? By all accounts, the source code (including future changes) for things such as ZFS will continue to be published under the CDDL. Will Oracle closing up development make it impossible for operating systems like FreeBSD to maintain ZFS without forking it? What do you think the ramifications will be for DragonFly’s HAMMER and DragonFly in general?
I’ve been NAS-shopping, and I’ve found that deduplication ability seems to add an extra zero on the end of a device’s price tag. It would be very nice for HAMMER.
I apologize; I’ve been missing. Here’s some misc links while I get back in gear:
- A very good reason to be interested in Hammer over ZFS: nobody will threaten lawsuits over Hammer.
- 10 tricks for admins. I’m posting it cause I can never remember that thing with tunneling ssh out. (via)
- This Gaming Life, as a free download. An excellent book that is in physical form on my shelf right now. Yes, unrelated.
If you have a Hammer filesystem, and you want to roll the entire thing back to a previous snapshot – all files, everywhere – it can be accomplished with one command.
A note, in part for my own benefit: the @reboot crontab entry is all you need to get a HAMMER mirror-stream going again after a reboot/shutdown.
Matthew Dillon went into detail on just how Hammer snapshots could be shared out via Samba.
Siju George is making a Hammer volume’s snapshots available through Samba, with the results that some Windows-using developers get historical snapshots for free.
Michael Neumann has fixed the ability to stream Hammer data between 32 and 64 bit systems. However, this is a change to 64-bit systems that requires them to match; make sure that you are not mixing 64-bit systems built before and after this commit on the 21st.
I can’t find the commit message in the mail archive, so I’ll quote it here:
Pulled from a larger conversation: a description of the settings for a HAMMER filesystem, and what they mean. I can tell from experience that extremely active disks will need extra cleanup time…
I can’t keep up with all the things to post. I desperately want to clear my inbox, so here’s a week’s worth of posts all smushed together. Enjoy!
- Naoya Sugioka’s tmpfs work is almost ready to go.
- Francois Tigeot is looking to find supported RAID hardware for DragonFly; the LSI1068e isn’t useable. Freddie Cash listed a number of different and fully supported cards, and Francois listed some other potential choices.
- While talking about hardware, Steve O’Hara-Smith reported excellent results with a particular Atom 330-based board and DragonFly.
- Stathis Kamperis has added to ‘hammer snapls’ output; an example is in his submit@message.
- The 2.6 release of DragonFly, scheduled for March, will have version 4 of HAMMER. 2.4 has version 2. Upgrading from version 2 to 4 can happen in place, live, and only needs to happen once per volume, not per PFS. That’s about as easy as it gets. More details are available.
- The default sshd config has been updated; this shouldn’t affect your normal operations unless you’re using one of the mentioned options.
- Oliver Fromme linked to more discussion of SSD durability.
- Also, Matthew Dillon posted more notes and benchmark numbers for his swapcache work. There’s been some side benefits too. A man page for swapcache is now available.
- Aggelos Economopoulos’s libevtr has been added, for event tracing. He’s posted some additional notes on this work-in-progress.
- We now have /var/log/daemon, too.
- Notes on prepping for Google Summer of Code 2010 from the GSOC Discussion list; I don’t know if that link is readable for nonsubscribers.
- The Definitive Guide to PC-BSD is out at the end of this short month. Dru writes good books.
- Did you know FreeCiv (a Civilization clone, of sorts) is playable in a web browser? Goodbye free time! Details are available at my favoritest game site.
If you’re running DragonFly 2.5 and updated in the past week or so, and have UFS disks, there’s some instability introduced by Matthew Dillon’s recent work. It ought to be better by next week.
Users of Hammer, or of UFS only as /boot, don’t have anything to worry about.
That didn’t take long: Matthew Dillon has an update on his REDO work; he’s about halfway there. His summary includes instructions on how to test this new work, including ways to change how Hammer syncs to disk.
Thanks to Michael Neumann, it’s now possible to remove a drive from a Hammer volume. It’s experimental, so all the standard warnings apply.
This can’t be done on a root volume, for hopefully obvious reasons.
Did you know you a Hammer volume can span multiple disks? And that you can add extra disks later on? There’s no RAID-like features – it’s just a straight multiple-disk volume, but it works. The Hammer command to do it is now “hammer volume-add“
Some of the ikiwiki configuration files on dragonflybsd.org were accidentally overwritten during a software upgrade. Normally this would mean some work to locate and replace them from backups, but since it was a Hammer volume, a quick look in /var/hammer/usr/… found them for me.
I want to point out what Hammer does, here. Restoring from backup isn’t new – it is in fact probably one of the most basic and necessary of system administration duties. However, Hammer makes it so easy that the incremental work of using it falls to almost nothing. There’s no extra preparation or syntax to learn for retrieval, which is wonderful. Hammer’s easy fix has helped me out several times now, saving me time that, while probably still successful with any other backup system, would have been taken up just restoring things back to normal.
Matthew Dillon has made version 4 of Hammer the default; the upgrade is a relatively painless ‘hammer upgrade’ command. This new version cuts out a chunk of the disk syncs needed, speeding up Hammer disk operations.
I like linkblogging, especially because there’s been a lot of good stuff floating about:
- Matthew Dillon detailed some of the problems he had using hardlinks to create backups – problems Hammer solves.
- The History of the Internet in a Nutshell: pretty good, though it says Unix “influenced” Linux and FreeBSD. Influenced is right for Linux, but there’s parts of the different BSDs that are from UNIX directly.
- From O’Reilly: The War for the Web. The walled garden that failed in the long run for Compuserve and AOL and so on is being resurrected. (via)
- Along the same lines: The Death of the URL.
Thomas Nikolajsen came up with some ideas for making the configuration files for a given Hammer volume accessible, even when that volume is being presented over NFS. He’s looking for more ideas.
If anyone wants a project, there’s apparently a small undo bug that I’ve encountered. It is a small fix in terms of changes, for any takers.
There’s a status report from Matthew Dillon about his work on version 4 of Hammer, including the always enjoyable stories of tests that involve yanking the SATA cable from the drive.
‘mike’ made this interesting csh script that allows autocompletion of Hammer sub-commands. e.g. type ‘hammer’ and then cycle through the available hammer commands as you would through file names.
This description of a Hammer bug makes for interesting reading, since it delves into the sequence of events where data is actually laid down on disk. Interesting reading for a geek, admittedly…
Version 3 of Hammer is now available in bleeding-edge DragonFly, though it’s still experimental. The biggest reason for this version bump is to move the /snapshots folder to /var for all Hammer filesystems. This means an accidental <tt>rm -rf</tt> won’t destroy snapshots, as I’ve done. The saved data is still on the original partition, as just the metadata is saved to /var. More explication is available.
Jan Lentfer performed some Postgres benchmarks on DragonFly. It’s elaborate enough that it’s in the form of a PDF attached to the message I’ve linked. There’s some additional variations that haven’t been tried yet.
Vigorous file system activity seemed to lower performance in the long term on Hammer, which is certainly something to investigate. More testing please!