In last month’s Storage Intelligence newsletter we discussed the latest Exchange storage system performance for 1001 to 5000 mailboxes. One charts we updated was the above Exchange database backup on a per server basis. The were two new submissions for this quarter, and both the Dell PowerEdge R730xd (#2 above) and the HP D3600 drive shelf with P441 storage controller (#10) ranked well on this metric.
This ESRP reported metric only measures backup throughput at a server level. However, because these two new submissions only had one server, it’s not as much of a problem here.
The Dell system had a SAS connected JBOD with 14-4TB 7200RPM disks and the HP system had a SAS connected JBOD with 11-6TB 7200RPM disks. The other major difference is that the HP system had 4GB of “flash backed write cache” and the Dell system only had 2GB of “flash backed cache”.
As far as I can tell the fact that the Dell storage managed ~2.3GB/sec. and the HP storage only managed ~1.1GB/sec is probably mostly due to their respective drive configurations than anything else.
RAID 0 vs. RAID 1
One surprising characteristic of the HP setup is that they used RAID 0 while the Dell system used RAID1. This would offer a significant benefit to the Dell system during heavy read activity, but as I understand it, the database backup activity is run with a standard email stress environment. So in this case, there is a healthy mix of reads/writes going on at the time the backup activity. So the Dell system would have an advantage for reads and a penalty for writes (writing two copies of all data). So Dell’s RAID advantage is probably a wash.
Whether RAID 0 vs. RAID 1 would have made any difference to other ESRP metrics (database transfers per second, read/write/log access latencies, log processing, etc.) is subject for another post.
Of course, with Exchange DAG’s there’s built in database redundancy so maybe RAID 0 is an OK configuration for some customers. Software based redundancy does seem to be Microsoft’s direction, at least since Exchange 2010, so maybe I’m the one that’s out of touch.
Still for such a small configuration I’m not sure I would have gone with RAID 0…