On Thu, 28 Jun 2012, Brian Candler wrote: > On Wed, Jun 27, 2012 at 05:28:43PM -0500, Nathan Stratton wrote: >> [root at virt01 ~]# dd if=/dev/zero of=foo bs=1M count=5k >> 5120+0 records in >> 5120+0 records out >> 5368709120 bytes (5.4 GB) copied, 26.8408 s, 200 MB/s >> >>> But doing a dd if=/dev/zero bs=1024k within a VM, whose image was mounted on >>> glusterfs, I was getting only 6-25MB/s. >> >> [root at test ~]# dd if=/dev/zero of=foo bs=1M count=5k >> 5120+0 records in >> 5120+0 records out >> 5368709120 bytes (5.4 GB) copied, 172.706 s, 31.1 MB/s > > That's what I consider unimpressive - slower than a single disk, when you > have an array of 16. I should try a pair of drbd nodes as a fair comparison > though. But wait, yes, I have 16 physical disks, but I am running distribute + replicate so the 8 physical boxes are broken up into 4 pairs of redundant boxes. When I do a write, I am writing on two servers, or 4 physical disks. So in my case, 31.1 MB/s vs about 200 MB/s native is not that bad. DRDB is MUCH faster, but your not comparing apples to apples. DRBD has worked great for me in the past when I only needed two storage nodes to be mirrored in active/active, but as soon as you grow past that you need to look at something like Gluster. With GlusterFS my single write is slower at 31.1 MB/s, but I can do that many many more times over my 8 nodes without losing I/O. > Having said that, multiple clients running concurrently should be able to > use the remaining bandwidth, so the aggregate throughput should be fine. Correct. ><> Nathan Stratton nathan at robotics.net http://www.robotics.net
