On Thu, May 13, 2010 at 3:19 AM, Roy Sigurd Karlsbakk <r...@karlsbakk.net>wrote:
> I've been reading a little, and it seems using WD Green drives isn't very > popular in here. Can someone explain why these are so much worse than > others? Usually I see drives go bad with more or less the same frequency... > > 1. They're 5900 RPM drives, not 7200, making them even slower than normal SATA drives. 2. They come with a idle timeout of 8 seconds, after which the drive heads are parked. This shows up as the Load Store counter in SMART output. They're rated for around 300,000 or 500,000 load cycle, which can happen in only a few short months on a server (we had over 40,000 in a week on one drive). On some firmware versions, this can be disabled completely using the wdidle3 DOS app. On other firmware versions, this can't be disabled, but can be set to 362 seconds (or something like that). Each time the heads are parked, it takes a couple of seconds to bring the drive back up to speed. This can drop your pool disk I/O through the floor. 3. The firmware on the drives disables the time-limited error reporting (TLER) feature, and it cannot be enabled like on other WD drives. 4. Some of the Green drives are "Advanced Format" with 4 KB sectors, except that the drives all lie and say they use 512 B sectors, leading to all kinds of alignment issues and even more slow-downs. No matter which firmware you run, you cannot get the drives to report on the actual physical size of a disk sector, it always reports 512 B. This makes it very hard to align partitions and filesystems, further degrading performance. If you are building a system that needs to be quiet and power efficient with 2 TB of storage, then maybe using a single WD Green drive would be okay. Maybe a home media server. However, going with 2.5" drives may be better. But for any kind of bulk storage setup or non-home-desktop setup, you'll want to avoid all of the WD Green drives (including the RE Green-power), and also avoid any 5900 RPM drives from other manufacturers (some Seagate 2 TB, for example). We made the mistake of putting 8 WD Green 1.5 TB drives into one of our storage servers, as they were on sale for $100 CDN. Throughput on that server has dropped quite a bit (~200 MB/s instead of the 300+ MB/s we had with all WD RE Black drives). It takes over 65 hours to resilver a single 1.5 TB drive, and a scrub on the entire pool takes over 3 days. When upgrading our secondary storage server, we went with Seagate 7200.11 1.5 TB drives. Re-silver of a drive takes under 35 hours (first drive was over 35 hours, 6th drive was just under). Haven't scrubbed the pool yet (still replacing drives in the raidz2 vdev). Performance has improved slightly, though. -- Freddie Cash fjwc...@gmail.com
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