Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> -----Original Message----- > From: drbd-user-bounces at lists.linbit.com > [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Ralf Gross > Sent: Sunday, January 14, 2007 5:33 PM > To: drbd-user at lists.linbit.com > Subject: Re: [DRBD-user] drbd performance with GbE in connected mode > > Ross S. W. Walker schrieb: > >> [drbd write performance over GbE] > > > > First of all let me ask which benchmark tool you used for the > > sequential/random io runs? I like the information it provides and > > can use a tool like that. > > It's tiobench (http://sourceforge.net/projects/tiobench/). > > > Second, using Prot C, the writes do not return until they are > > committed to disk on both sides, so cannot the loss of throughput be > > attributed to the increased latency of writing on host1 while it > > sends out the write over 1Gbps wire to host2, who then writes it to > > disk and then sends a successful response back to host1 who then > > returns? > > > > If the local write and send happened at the same time Copy/Send > > Latency + Gbps latency + Remote Write Latency + Gbps return latency > > = increased latency. How much increased latency depends on the > > speed/effectiveness of the network and the speed of the remote > > storage versus the speed of the local storage. The slowest storage > > is always the weakest link, try to get storage systems that are the > > same for most reliable performance. > > Both Raid's are able to write with >120MB/s in disconnected mode. > I'm just wondering because I have seen people on the list that get > ~95MB/s with a similar setup. There's lies, damn lies, then benchmarks. Pump a big enough block size to the storage till you get the throughput you like. Some people throw 1MB block size and get 115MB/s throughput. I always like to use the block sizes my application uses. If it's ext2 then 4K is a good benchmark, but different apps use different block sizes. Always ask the block size and io pattern for the benchmarks people throw around. -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.