[Lustre-discuss] How smart is Lustre?
Allen, Benjamin S
bsa at lanl.gov
Wed Dec 19 10:22:23 PST 2012
1. You provide Lustre, when formatting with mkfs.lustre, a standard block device. If you want Lustre to use the multi-pathed device, you'll need to setup Linux MPIO, then use the multi-pathed device path.
Failover between redundant OSS or MDS is not controlled by Lustre either. You will need to setup a corosync + pacemaker or similar type fail-over service.
2. Having two paths to your storage should speed things up. I'm guessing you'd have more than one LUN on the array, so you could do something as simple as splitting the LUNs between the two paths, or use round robin to balance the traffic between the two paths, etc.
3. Totally dependent on the whole system. Start sketching out the entire system starting at the disks, all the way to your clients. Figure out the best case throughput numbers for each part of the system (disks -> disk interconnect -> array controller -> array interconnect to host -> FS Throughput on OSS/MDS -> OSS/MDS network throughput -> switch throughput -> aggregate clients network throughput …, etc ). This will start giving you a basic idea of where your bottlenecks are. Adjust your design to relieve some of the identified bottlenecks if budget allows. Remember vendors are likely to overestimate throughput numbers or give benchmarks that don't match your workload. As such it's best to get your hands on the hardware and test it out yourself.
4. Many if not most storage arrays will functionally work with Lustre. Which will work best in your environment, is largely dependent on your expected work load.
On Dec 19, 2012, at 10:36 AM, Jason Brooks wrote:
I am building a 2.3.x filesystem right now, and I am looking at setting up some active-active failover abilities to my oss's. I have been looking at Dell's md3xxx arrays, as they have redundant controllers, and allow up to four hosts to connect to each controller.
I can see how linux multi-path can be used with redundant disk controllers. I can even (slightly) understand how lustre fails over when an oss goes down.
1. Is lustre smart enough to use redundant paths, or failover oss's if an oss is congested? (it would be cool, no?)
2. Does the linux multi-path module slow performance?
3. How much does a raid array such as the one listed above act as a bottleneck, say if I have as many volumes available on the raid controllers as there are oss hosts?
4. Are there arrays similar to Dell's model that would work?
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