On Mon, May 17, 2010 at 9:25 AM, Tomas Ögren <st...@acc.umu.se> wrote:
> On 17 May, 2010 - Dan Pritts sent me these 1,6K bytes: > > > On Thu, May 13, 2010 at 06:09:55PM +0200, Roy Sigurd Karlsbakk wrote: > > > 1. even though they're 5900, not 7200, benchmarks I've seen show they > are quite good > > > > Minor correction, they are 5400rpm. Seagate makes some 5900rpm drives. > > > > The "green" drives have reasonable raw throughput rate, due to the > > extremely high platter density nowadays. however, due to their low > > spin speed, their average-access time is significantly slower than > > 7200rpm drives. > > > > For bulk archive data containing large files, this is less of a concern. > > > > Regarding slow reslivering times, in the absence of other disk activity, > > I think that should really be limited by the throughput rate, not the > > relatively slow random i/o performance...again assuming large files > > (and low fragmentation, which if the archive is write-and-never-delete > > is what i'd expect). > > > > One test i saw suggests 60MB/sec avg throughput on the 2TB drives. > > That works out to 9.25 hours to read the entire 2TB. At a conservative > > 50MB/sec it's 11 hours. This assumes that you have enough I/O bandwidth > > and CPU on the system to saturate all your disks. > > > > if there's other disk activity during a resilver, though, it turns into > > random i/o. Which is slow on these drives. > > Resilver does a whole lot of random io itself, not bulk reads.. It reads > the filesystem tree, not "block 0, block 1, block 2..". You won't get > 60MB/s sustained, not even close. > > Resilver time for a 1.5 TB WD Green drive, with wdidle3 setting "disabled", in an 8-drive raidz2 vdev, is over 65 hours, with ~500 GB of data per drive. We just replaced 8 WD 500 GB RE Black drives with 8 1.5 TB WD Green drives, not realising just how horrible of a drive these are. :( So much for the $100 CDN bargain price. Resilver time for a 1.5 TB Seagate 7200.11 drive, in an 8-drive raidz2 vdev, is about 35 hours, with ~ 500 GB of data per drive. We just replaced 8 WD Black 500 GB drives and Seagate 7200.11 500 GB drives with 8 1.5 TB Seagate 7200.11. Much nicer drives, and way better performance than the WD Greens. Both servers are identical hardware (motherboard, CPU, RAM, RAID controllers, etc), both are using ZFSv14. The first is 64-bit FreeBSD 7.3-RELEASE, the second is FreeBSD 8-STABLE. For a home media server, the WD Greens may be okay. For anything else, they're crap. Plain and simple. -- Freddie Cash fjwc...@gmail.com
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