[Lustre-discuss] Storage management question

[Andy Pace]

I've got a small Lustre lab setup with the following server specs:

2 X OSS'S:
Dual Xeon 5410
4X1TB HDD @ RAID10
16G of RAM

1 X MDS:
Dual Xeon 5410
4X1TB HDD @ RAID10
16G of RAM
(I know this may be overkill, but I included it just for reference)

We plan on running virtual instances and using this Lustre storage pool for each instance's storage. Right now, no striping is enabled (until we figure out the redundancy side), but what I'm wondering is how the metadata handles the move (if at all) of data if one of the OSS's runs out of data.

Here's a scenario:

Instance #1 -> MDS sends to OSS1
Instance #2 -> MDS sends to OSS2
Instance #3 -> MDS sends to OSS1

Suddenly both instance #1 and #3 consume all available storage on OSS1. What happens then? Does the MDS send any further writes to OSS2? As far as I know there is no way to move around data using the MDS to a different OSS, so I'm a bit confused. Striping may slow this specific scenario down, but the lack of resiliency is something we're still testing - dabbling with DRBD.

Thanks in advance for any comments or suggestions :)

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