> On 01 Aug 2016, at 19:30, Michelle Sullivan <miche...@sorbs.net> wrote:
> There are reasons for using either…
Indeed, but my decision was to run ZFS. And getting a HBA in some
configurations can be difficult because vendors insist on using
RAID adapters. After all, that’s what most of their customers demand.
Fortunately, at least some Avago/LSI cards can work as HBAs pretty well. An
example is the now venerable LSI2008.
> Nowadays its seems the conversations have degenerated into those like Windows
> vs Linux vs Mac where everyone thinks their answer is the right one (just as
> you suggested you (Borja Marcos) did with the Dell salesman), where in
> reality each has its own advantages and disadvantages.
I know, but this is not the case. But it’s quite frustrating to try to order a
server with a HBA rather than a RAID and receiving an answer such as
“the HBA option is not available”. That’s why people are zapping, flashing and,
generally, torturing HBA cards rather cruelly ;)
So, in my case, it’s not about what’s better or worse. It’s just a simpler
issue. Customer (myself) has made a decision, which can be right or wrong.
Manufacturer fails to deliver what I need. If it was only one manufacturer,
well, off with them, but the issue is widespread in industry.
> Eg: I'm running 2 zfs servers on 'LSI 9260-16i's... big mistake! (the ZFS,
> not LSI's)... one is a 'movie server' the other a 'postgresql database'
> server... The latter most would agree is a bad use of zfs, the die-hards
> won't but then they don't understand database servers and how they work on
> disk. The former has mixed views, some argue that zfs is the only way to
> ensure the movies will always work, personally I think of all the years
> before zfs when my data on disk worked without failure until the disks
> themselves failed... and RAID stopped that happening... what suddenly
> changed, are disks and ram suddenly not reliable at transferring data? ..
> anyhow back to the issue there is another part with this particular hardware
> that people just throw away…
Well, silent corruption can happen. I’ve seen it once caused by a flaky HBA and
ZFS saved the cake. Yes. there were reliable replicas. Still, rebuilding would
be a pain in the ass.
> The LSI 9260-* controllers have been designed to provide on hardware RAID.
> The caching whether using the Cachecade SSD or just oneboard ECC memory is
> *ONLY* used when running some sort of RAID set and LVs... this is why LSI
> recommend 'MegaCli -CfgEachDskRaid0' because it does enable caching.. A good
> read on how to setup something similar is here:
> https://calomel.org/megacli_lsi_commands.html (disclaimer, I haven't parsed
> it all so the author could be clueless, but it seems to give generally good
> advice.) Going the way of 'JBOD' is a bad thing to do, just don't,
> performance sucks. As for the recommended command above, can't comment
> because currently I don't use it nor will I need to in the near future... but…
Actually it’s not a good idea to use heavy disk caching when running ZFS. Its
reliability depends on being able to commit metadata to disk. So I don’t care
about that caching option. Provided you have enough RAM, ZFS is very effective
caching data itself.
> If you (O Hartmann) want to use or need to use ZFS with any OS including
> FreeBSD don't go with the LSI 92xx series controllers, its just the wrong
> thing to do.. Pick an HBA that is designed to give you direct access to the
> drives not one you have to kludge and cajole.. Including LSI controllers with
> caches that use the mfi driver, just not those that are not designed to work
> in a non RAID mode (with or without the passthru command/mode above.)
As I said, the problem is, sometimes it’s not so easy to find the right HBA.
> So moral of the story/choices. Don't go with ZFS because people tell you its
> best, because it isn't, go with ZFS if it suits your hardware and
> application, and if ZFS suits your application, get hardware for it.
Indeed, I second this. But really, "hardware for it" covers a rather broad
cathegory ;) ZFS can even manage to work on hardware _against_ it.
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