On Wed, 16 Oct 2002 05:15:33 +0400, "Hans Reiser" <[EMAIL PROTECTED]> said: > JP Howard wrote: > > >We've been thinking about something like that, using this extremely nifty > >trick: > > > >http://www.mikerubel.org/computers/rsync_snapshots/ > > > This is brilliantly simple. > I thought so too. I'm cc'ing the author so he can bask in the glory... ;-) > > > >Back in the old days (i.e. last week) when we were planning around Ext3, > >we were thinking of combining it with this product: > > > >http://www.shaolinmicro.com/product/cogofs/index.php > > > This looks reasonable as a product, and not unreasonably expensive for > servers. There are some advantages to tight integration though, in > that you can compress at flush time. > Yes indeed. And I haven't seen this product used anywhere--I don't know how reliable it is. It's binary-only, which I don't like, and you have to get a version for your particular kernel (and really, who uses stock kernels?...) > > > >The two combined, with ATA RAID, provide fast, redundent, incremental, > >compressed backups. > > > >Does ReiserFS support transparent compression? > > > This is one of the features that won't make the Halloween deadline, but > might be slipped in later. > > If not, are there any > >plans in this direction? Benchmarks I've seen in the past suggest that > >compressed file systems generally improve performance (especially when > >using something fast like LZOP) since CPUs are so fast--and of course for > >backups being able to store more on fewer disks is nice... > > > What I had heard was that they generally slowed peformance, but maybe my > info is old. > > CPUs are faster now, and maybe compression algorithms are faster. > > Can you give more details? > I'm just passing on anecdotal information, I'm afraid. I can tell you that LZOP is *seriously* fast. http://www.oberhumer.com/opensource/lzop/
Every benchmark I've seen shows it #1 for speed. We see around 50% compression ratio on our Cyrus mail store using LZOP compression on our backups. It's easy enough to construct some simple benchmarks like this: ---- # time zgrep foobar maillog.1.gz real 0m6.924s user 0m3.140s sys 0m0.620s # time grep foobar maillog.1 real 0m19.972s user 0m0.290s sys 0m0.620s ---- Of course, it depends a lot on the CPU and HDD configuration, and where your system is loaded. We always find our IMAP and SMTP servers IO bound, with plenty of CPU free. It's very expensive to change from a 5x73GB to a 10x36GB config, so buying more IO performance is an expensive proposition.
