On Fri, 2014-08-15 at 08:05 -0400, Ron Kerry wrote:
On 8/15/14, 8:03 AM, Lars Marowsky-Bree wrote:
On 2014-08-15T07:57:31, Ron Kerry <rkerry@sgi.com> wrote:
True enough, but the performance of an active-active HA configuration with two or more nodes serving NFS or CIFS can be well in excess of what a single server is capable of doing. This all depends on the underlying disk hardware. Many time that hardware may be capable of far more bandwidth than a single server can drive by itself. In this active-active clustered environment the performance achievable by any single node will be less than what it can do on its own, but the combined performance of many nodes to the same shared-clustered disk will be able to reach the bandwidth capability of the underlying disk hardware.
... but in this case, the shared storage is provided by drbd, so the *write* performance of the combined setup is limited to the slowest of the two disks, and the network interconnect, and also reduced by the locking needed by OCFS2.
Read-performance could theoretically benefit, yes.
There's however also the higher complexity of an active/active environment, and the tighter coupling of the nodes which reduces their ability to cope with faults.
Personally, I'd probably avoid this setup, unless there was a really substantial reason for it.
I missed that the underlying storage was DRBD. I agree totally, there is little benefit to this sort of configuration - performance or availability except for certain particular sorts of workloads and failure scenarios.
We are amazed that obviously knowledgeable engineers are questioning the availability advantages of a 2 node cluster that keeps us all working over a single file server which doesn't if it fails! But OK, we'll scrap this idea. We have a mix of 80 linux and xp computers, some of which are over 10 years old. Our file servers are second hand computers which a bank were throwing out. We want to keep working. We have €150 and 2 old AMD computers. What do you recommend? L x
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Ron Kerry rkerry@sgi.com Global Product Support - SGI Federal
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