Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On 20/12/12 19:56, Felix Frank wrote: > On 12/20/2012 08:31 AM, Adam Goryachev wrote: >> The primary has 5 x 480G Intel SSD drives in a RAID5 configuration >> The secondary has 4 x 2TB WD RE4 drives in a RAID10 configuration > > Huh. SSD RAID vs. rotaries? That's about as far apart as you can set > primary and secondary performance-wise. Have you considered switching > their roles? Ummm, no, I need the primary to be fast enough for the work-load... > If I understand this correctly, you're looking for a way to keep your > maximum performance and trade in the stability of your replication. Are > you sure the gain is wort the risk (and pain)? Is your iSCSI maxing out > the I/O on that SSD RAID? No, the I/O on the SSD is not significant... at least, I don't think it is.... I thought that since the secondary is a write only mirror, it doesn't have as much seek overhead because it never has to seek for a read. ie, if 40% of all disk I/O is a read request, then the secondary has 40% less load compared to the primary. I hoped that avoiding RAID5 (using RAID10) on the secondary would allow it to be "good enough". >> In general, most of those are small amounts of data over small amounts >> of time, so it would be nice to add a little more buffering 'somewhere' >> so that instead of getting out of sync, the secondary just has more data >> un-written to disk in a buffer somewhere. >> >> Any suggestions or advice would be greatly appreciated. > > DRBD Proxy springs to mind, even though that's not a free option > (monetarily speaking). Thanks, I am aware of that option, and have already proposed that as a solution, but spending that kind of money is not an option at the moment. I found performance improved after tuning some of the options in drbd, and was either looking for other parameters to tune (or test/etc) to find the bottleneck or solve the bottleneck (at least a little). However, I didn't find a specific formula for setting those options, and I don't think its a great option to tweak options and just hope for the best... I think I've mentioned before the following options that I am currently using: max-buffers 16000; max-epoch-size 16000; unplug-watermark 8192; sndbuf-size 512k; on-congestion pull-ahead; Regards, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au