The system is freshly installed and the pools are newly created as well. The tests have been repeated with new pools recreated with different disks of the same model (Seagate ES.2).
On Oct 28, 2011, at 5:58 AM, Erik Forsberg wrote: > Indeed. Just recently had very noticeable performance issues > on a zfs pool that became 75% full. Fell of a cliff basically. > Didnt expect that until well above 80%. Now, this was Solaris 10u8 > or somewhere around that. Deleted un-needed files back to 55% and > performance is excellent again. > >> -- Original Message -- >> Date: Thu, 27 Oct 2011 14:33:25 -0700 >> From: Erik Trimble <tr...@netdemons.com> >> To: zfs-discuss@opensolaris.org >> Subject: Re: [zfs-discuss] Poor relative performance of SAS over SATA drives >> >> >> It occurs to me that your filesystems may not be in the same state. >> >> That is, destroy both pools. Recreate them, and run the tests. This >> will eliminate any possibility of allocation issues. >> >> -Erik >> >> On 10/27/2011 10:37 AM, weiliam.hong wrote: >>> Hi, >>> >>> Thanks for the replies. In the beginning, I only had SAS drives >>> installed when I observed the behavior, the SATA drives were added >>> later for comparison and troubleshooting. >>> >>> The slow behavior is observed only after 10-15mins of running dd where >> >>> the file size is about 15GB, then the throughput drops suddenly from > >>> 70 to 50 to 20 to <10MB/s in a matter of seconds and never recovers. >>> >>> This couldn't be right no matter how look at it. >>> >>> Regards, >>> WL >>> >>> >>> >>> On 10/27/2011 9:59 PM, Brian Wilson wrote: >>>> On 10/27/11 07:03 AM, Edward Ned Harvey wrote: >>>>>> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- >>>>>> boun...@opensolaris.org] On Behalf Of weiliam.hong >>>>>> >>>>>> 3. All 4 drives are connected to a single HBA, so I assume the mpt_sas >>>>> driver >>>>>> is used. Are SAS and SATA drives handled differently ? >>>>> If they're all on the same HBA, they may be all on the same bus. It >> >>>>> may be >>>>> *because* you're mixing SATA and SAS disks on the same bus. I'll >>>>> suggest >>>>> separating the tests, don't run them concurrently, and see if >>>>> there's any >>>>> difference. >>>>> >>>>> Also, the HBA might have different defaults for SAS vs SATA, look in >> >>>>> the HBA >>>>> to see if write back / write through are the same... >>>>> >>>>> I don't know if the HBA gives you some way to enable/disable the >>>>> on-disk >>>>> cache, but take a look and see. >>>>> >>>>> Also, maybe the SAS disks are only doing SATA. If the HBA is only > >>>>> able to >>>>> do SATA, then SAS disks will work, but might not work as optimally > >>>>> as they >>>>> would if they were connected to a real SAS HBA. >>>>> >>>>> And one final thing - If you're planning to run ZFS (as I suspect >>>>> you are, >>>>> posting on this list running OI) ... It actually works *better* >>>>> without any >>>>> HBA. *Footnote >>>>> >>>>> *Footnote: ZFS works the worst, if you have ZIL enabled, no log >>>>> device, and >>>>> no HBA. It's a significant improvement, if you add a battery backed >> or >>>>> nonvolatile HBA with writeback. It's a signfiicant improvement >>>>> again, if >>>>> you get rid of the HBA, add a log device. It's a significant >>>>> improvement >>>>> yet again, if you get rid of the HBA and log device, and run with ZIL >>>>> disabled (if your work load is compatible with a disabled ZIL.) >>>>> >>>>> _______________________________________________ >>>>> zfs-discuss mailing list >>>>> zfs-discuss@opensolaris.org >>>>> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >>>> >>>> First, ditto everything Edward says above. I'd add that your "dd" >>>> test creates a lot of straight sequential IO, not anything that's >>>> likely to be random IO. I can't speak to why your SAS might not be > >>>> performing any better than Edward did, but your SATA's probably >>>> screaming on straight sequential IO, where on something more random > I >> >>>> would bet they won't perform as well as they do in this test. The >>>> tool I've seen used for that sort of testing is iozone - I'm sure >>>> there are others as well, and I can't attest what's better or worse. >>>> >>>> cheers, >>>> Brian >>>> >>> >>> _______________________________________________ >>> zfs-discuss mailing list >>> zfs-discuss@opensolaris.org >>> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >> >> _______________________________________________ >> zfs-discuss mailing list >> zfs-discuss@opensolaris.org >> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
