On Monday 27 July 2009 15:21:17 Alan Brown wrote: > On Fri, 24 Jul 2009, Marc Cousin wrote: > > All you really need is to be able to read and write big streams at the > > same time. So the real problem is to help your disk scheduler to be able > > to read while having a lot of data in the write cache. > > How many streams are you handling simultaneously. >
Sorry, it took me a while to get that information ... At peak during the night, we have around 40-50 write streams at the same time, and we are despooling to 3 LTO3 and 3 LTO1. Load is sustained around 250MB/s for reads from spool and 300MB/s for writes to spool. Of course, the disk array costs more than 2 64GB X25-E ... But at the same time, 128 GB would be really small for us. Anyway, the purpose of my message wasn't to tell "don't buy SSD". You'll have better throughput with 1 SSD than with 1 SCSI 15k drive. But you could purchase a good controller and normal (SCSI 10k or maybe SATA) drives, and have a similar or better throughput with more that a few minutes worth of spool (128GB is roughly 5 minutes here :) ) I think the most important is : don't purchase anything without doing benchmarks first for this special type of activity. That's what we did : we wrote a small program to simulate the expected throughput on the array with several streams, and only bought the array when we were satisfied with its performance, which required a bit of tuning (choose the right filesystem, the right scheduler, tune read ahead...). And I think this time wasn't wasted at all... ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users