Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Wed, Mar 18, 2009 at 09:46:53AM +0000, Gordan Bobic wrote: > Can you post the contents your /proc/drbd? > You might also want to add "no-disk-drain", and see if that helps. No. Don't use no-disk-drain, especially if you already use all the other "no-disk-whatever" options. Because that will in most real-life setups cause write reordering where it is not allowed. Which means journalling file system or data base assumtions are violated. If you run into data consistency issues, lose files or transactions, after failover or crash on DRBD with no-disk-drain, don't blame DRBD. Similar, if you run on volatile caches, don't blame DRBD. > > > > #dd if=/dev/zero of=/dev/sdb bs=512k count=1000 oflag=direct > > 524288000 bytes (524 MB) copied, 15.0304 seconds, 34.9 MB/s so your backend storage is capable of 35 MB/s throughput, which is just about ok for a single disk. > > # dd if=/dev/zero of=/dev/sdb bs=512 count=1000 oflag=direct > > 512000 bytes (512 kB) copied, 0.351227 seconds, 1.5 MB/s and ~ 0.35 ms latency, which means there are caches involved. hopefully they are non-volatile. but probably its just a single low end IDE disk, with volatile on disk cache enabled? > > ##### without flushes: > > #single node > > # dd if=/dev/zero of=/dev/drbd0 bs=512k count=1000 oflag=direct > > 524288000 bytes (524 MB) copied, 15.0428 seconds, 34.9 MB/s > > > > # dd if=/dev/zero of=/dev/drbd0 bs=512 count=1000 oflag=direct > > 512000 bytes (512 kB) copied, 0.367788 seconds, 1.4 MB/s yep, about the same. ok. > > #dual node > > # dd if=/dev/zero of=/dev/drbd0 bs=512k count=1000 oflag=direct > > 524288000 bytes (524 MB) copied, 51.0372 seconds, 10.3 MB/s so your network is a 100 MBit connection? > > # dd if=/dev/zero of=/dev/drbd0 bs=512 count=1000 oflag=direct > > 512000 bytes (512 kB) copied, 2.03025 seconds, 252 kB/s with an approximate RTT of 2 ms? -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. __ please don't Cc me, but send to list -- I'm subscribed