Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hardware this time: 2 Sun Fire v20z, which are dual Opteron (250) machines with 4GB Ram. The Raid-controller identifies itself as LSI Logic / Symbios Logic 53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI, and some nice SCSI disks. The disks set up as RAID1 array. For the courious I am using a inofficial Debian Sarge port to amd64 as distribution. LVM2 is used as a middle layer, DRBD on lop of LVs. Raw write performance to the LVs: 59.69 MB/sec (3221225472 B / 00:51.468961) 60.54 MB/sec (3221225472 B / 00:50.743192) 60.71 MB/sec (3221225472 B / 00:50.603030) Once again I was curious how inhomogen the performance on the disks is, and here are the results from an other (later allocated) LV are: 56.07 MB/sec (3221225472 B / 00:54.784013) 56.60 MB/sec (3221225472 B / 00:54.279036) 57.06 MB/sec (3221225472 B / 00:53.838054) Resync done (total 59 sec; paused 0 sec; 53316 K/sec) DRBD's syncer ran on average in the area of >50MB/sec, afterwards I limited it to 15MB/sec for production purposis. Here are the values for mirrored writes. Protocol C with an MTU of 1500. 38.88 MB/sec (3221225472 B / 01:19.004518) 38.12 MB/sec (3221225472 B / 01:20.589348) 38.39 MB/sec (3221225472 B / 01:20.020814) Then I changed the MTU of the networking cards to 6000, CPU ussage on the secondary side dropped from about 18 % to 9% . Performance is abot the same: 39.64 MB/sec (3221225472 B / 01:17.488087) 38.48 MB/sec (3221225472 B / 01:19.824027) 38.41 MB/sec (3221225472 B / 01:20.020814) These values were quite lower than what I expected, since on the last pair of machines I did test on, DRBD's overhead was lower than the inhomogenity of the disks. On this pair of machines we get with DRBD only 65% of the performance we have without DRBD. A hint where we loose are the numbers from writing on DRBD in disconnected mode: 41.45 MB/sec (3221225472 B / 01:14.113481) 41.05 MB/sec (3221225472 B / 01:14.829909) 41.09 MB/sec (3221225472 B / 01:14.763764) DRBD instructs the IO subsystem to submit 4KB at most in a single BIO, while LVM most probabely allows bigger BIOs. Maybe this is an area where we will optimize/improve DRBD in the future... OTOH it is interesting that the syncer was able to do more than 41MB/sec ... Interesting stuff, unforunately these machines go to some data center by the end of next week, then I have to use my rather old development machines again.... -Philipp -- : Dipl-Ing Philipp Reisner Tel +43-1-8178292-50 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Schönbrunnerstr 244, 1120 Vienna, Austria http://www.linbit.com :