I meant to say, ARC will cache reads, not writes > On 16 Jun 2015, at 1:11 PM, David Finster <[email protected]> > wrote: > > The potential road-block that I’d look out for is whether the on-board SATA > that is currently in the box is supported by SmartOS/illumos. If not, then it > would be a matter of dropping a compatible HBA (LSI SAS are the crowd > favourite) with a SAS->SATA fan-out. > > Running a Windows KVM with a database server on SATA disks without an SLOG is > a bit of a recipe for bad performance. That being said, it obviously depends > on the underlying zpool layout/disk characteristics/database performance > expectations and workload. It is worth noting that all writes inside a KVM > are treated as synchronous writes, which is what drags performance down. This > can be mitigated by using an SSD-based SLOG. The degree to which it is > mitigated depends on the performance of the SSD you use - the lower > latency/higher IOPS the drive offers, the better the result. I would also > look for an SSD with power protection/super caps, just to be sure your writes > are actually available form the SLOG should the worst happen. > > I’m not aware of any SmartOS users using PCI-SSDs and I’m not sure they are > supported (beyond SATA/SAS drive emulation). There is some activity within > illumos around building an NVMe driver to take full advantage of PCI based > SSDs. AFAIK, most people use either a SATA/SAS based SSD. A popular SATA > drive is the Intel DC S3700 200GB model (has higher IOPS/throughput than the > 100GB) and we’ve just been deploying HGST Ultrastar SSD800MH.B drives and are > seeing write speeds of 477 MB/sec inside a KVM. > > You’ll certainly see better overall performance by using mirrors rather than > RAIDZ and for 4 disks it would probably be your best option overall. It would > probably be worth just trying what you have now and seeing if it works to a > satisfactory level. > > Keep in mind that ZFS has ARC and will use RAM to cache your most common > writes. Ideally, much of the data involved in the database should be fed from > RAM rather than real reads from disk, so your read requirements might not be > that high in reality. > >> On 16 Jun 2015, at 12:49 PM, Jack Downes <[email protected]> wrote: >> >> I'd have to echo Sebastian mostly. Zfs is great, but the underlying >> hardware is... what is. add another 1 tb drive and put that as Raid 10 >> (stripe the mirrors), and it'll perform pretty decently. You'd be surprised. >> If you have the money, yeah, SSD is fantastic, but wow... if you are trying >> to get reasonable size, you'll spend some cash. Perhaps in this case that >> doesn't matter. If you have the money for SSD drives, you might consider >> getting 4 reasonable 2TB drives (they sell them for $50 each on >> gohardrive.com anymore for WD RE4 or Hitachi Ultrastars now), and then >> putting some budget into a smartOS compatible PCI-SSD drive. Be careful on >> that - it's easy to get the wrong drive, but it's not that hard to get the >> right one either! That way you'd have your 4 spindles, raid 10 with a slog, >> it'd be decent that way, IMHO. >> >> On 06/15/2015 07:07 PM, [email protected] wrote: >>> one of my clients owns a supermicro-based box with 4 hot-swap sata bays. it >>> has integrated SATA and (i believe) no SAS. the original admin populated it >>> with (3) 1TB SATA disks and commissioned it as a fileserver (simple raid5). >>> it has 32GB of memory. the box is no longer being used, so it's been >>> allocated to me for the purpose of hosting another windows server. i'd like >>> to virtualize the server via smartos/kvm but i have reservations. >>> >>> i believe i can get away with using only 16GB for VMs, so that leaves 16GB >>> for smartos/zfs - i think that'll probably work well. but i seriously doubt >>> those disks will give anything resembling decent performance. i only have 4 >>> bays to work with, and only one is currently free. for a windows server VM >>> hosting a multi-user database, would adding a SATA SSD as log device for >>> the zones zpool keep me out of hot water here or is this just not going to >>> work? >>> >>> obviously i can try to source a supported SAS controller and disks, but i'm >>> wondering if i can actually get by with SATA ... what if i filled the (4) >>> 3.5" bays with SSDs and striped across two mirrors? would that mostly >>> guarantee decent performance, or will that just waste time and money? >>> >>> experienced opinions greatfully accepted! >>> >>> >>> ------------------------------------------- >>> smartos-discuss >>> Archives: https://www.listbox.com/member/archive/184463/=now >>> RSS Feed: >>> https://www.listbox.com/member/archive/rss/184463/26849696-e427f2da >>> Modify Your Subscription: https://www.listbox.com/member/?&; >>> Powered by Listbox: http://www.listbox.com >> >> -- >> Jack Downes >> >> >> >> ------------------------------------------- >> smartos-discuss >> Archives: https://www.listbox.com/member/archive/184463/=now >> RSS Feed: https://www.listbox.com/member/archive/rss/184463/25738179-216c4b5f >> Modify Your Subscription: https://www.listbox.com/member/?&; >> Powered by Listbox: http://www.listbox.com > > > > ------------------------------------------- > smartos-discuss > Archives: https://www.listbox.com/member/archive/184463/=now > RSS Feed: https://www.listbox.com/member/archive/rss/184463/25738179-216c4b5f > Modify Your Subscription: https://www.listbox.com/member/?&; > Powered by Listbox: http://www.listbox.com
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