LARGE single-system Cyrus installs?

[David Carter]

On Fri, 5 Oct 2007, Bron Gondwana wrote:

> We ran over 100,000 users on a single backend for over a year without
> problems, but then we had a RAID array failure (3 disks within a day)
> with 2Tb of data on a single RAID unit

We have pretty much given up on RAID 5 because of the reconstruct times 
with large disks. Our new systems are 12 disk RAID 10 (plus hot spares).

I think that gives about the same usable capacity as your 2 x RAID5 +
2 x RAID1 setup, but better redundancy. There would be twice as much
work to restore the single RAID 10 set if it failed.

I plan some experiments with split meta next year. My gut feeling is that 
12 slow disks will be better than 4 faster disks given the short command 
queues in SATA NCQ, but I'm entirely willing to be proved wrong. Multiple 
partitions would certainly help with any bottlenecks at the VFS layer.

I suppose that 8 SATA disks for the data and four 15k SAS disks for the 
metadata would be a good mix.

-- 
David Carter                             Email: David.Carter at ucs.cam.ac.uk
University Computing Service,            Phone: (01223) 334502
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