On 20/04/2013 17:00, Tanstaafl wrote: > Thanks for the responses so far... > > Another question - are there any caveats as to which filesystem to use > for a mail server, for virtualized systems? Ir do the same > issues/questions apply (ie, does the fact that it is virtualized not > change anything)? > > If there are none, I'm curious what others prefer. > > I've been using reiserfs on my old mail server since it was first set up > (over 8 years ago). I have had no issues with it whatsoever, and even > had one scare with a bad UPS causing the system to experienc an unclean > shutdown - but it came back up, auto fsck'd, and there was no 'apparent' > data loss (this was a very long time ago, so if there had been any > serious problems, I'd have known about it long go). > > I've been considering using XFS, but have never used it before. > > So, anyway, opinions are welcome...
Virtualization can change things, and it's not really intuitive. Regardless of what optimizations you apply to the VM, and regardless of what kind of virtualization is in use on the host, you are still going to be bound by the disk and fs behaviour of the host. If VMWare gives you a really shitty host driver, then something really shitty is going to be the best you can achieve. Disks aren't like eg NICs, you can't easily virtualize them and give the guest exclusive access in the style of para-virtualization (I can't imagine how that would even be done). You also didn't mention what mail server you use - implementations vary a great deal. Gut feel tells me that unless you are dealing with many 1000s of mails in a short period you won't really need XFS's aggressive caching. But I'm happy to be proved wrong and numbers tell the truth :-) I think the best you will get here is a list of combinations that are unlikely to suit, and you will have to do your own extensive testing to find what works best in your area. FWIW, I have two mail relays (no mail storage) running old postfix versions on FreeBSD. I expected throughput to differ when virtualized on ESXi, but in practice I couldn't see a difference at all - maybe the mail servers were very under-utilized. Considering this pair deal with anything between 500,000 to a million mails a day total, I would not have considered them "under-utilized". Just goes to show how opinions are often worthless but numbers buys the whiskey :-) -- Alan McKinnon [email protected]
