Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
>> Hi there I am using DRBD 0.7.21 with iSCSI Enterprise Target 0.4.14 on >> CentOS 4.4. >> >> When I run iSCSI direct to the LVM lv on top of hardware RAID I can get >> 225 MB/s over two sessions in MPIO with 256K block size, but when I put >> DRBD in-between iSCSI and LVM the throughput tops out at 80 MB/s and I >> can't seem to go over that. >> >> DRBD seems to report it's max number of sectors as 8 (4K), does that >> mean each io operation is limited to 4K? My hardware raid reports it's >> max sectors as 128, could this explain the reduction to 1/3 throughput? >> > > Hi, > > The cause for the limitation to 4k is the Linux-2.4 compabitility of > DRBD-0.7. > > Repeat your test with drbd-8.0(rc1). > > drbd-8.0 will do BIOs up to 32k, but much more important are other > changes (e.g. the non blocking make_request() function), that makes > drbd-8.0 to scale much better with high end hardware. > I guess many 0.7.x users could benefit from the 32k BIO's. Is it trivial to patch 0.7.x? ( Without breaking 2.4 support using a 'configure --with-large-bio' )