24.12.2010 16:01, Krzysztof Halasa wrote: > Rogier Wolff <R.E.Wolff@xxxxxxxxxxxx> writes: > >> ata6.00: 1953525168 sectors, multi 16: LBA48 NCQ (depth 0/32) >> scsi 5:0:0:0: Direct-Access ATA WDC WD10EARS-00Y 80.0 PQ: 0 ANSI: 5 >> sd 2:0:0:0: [sda] 1953525168 512-byte logical blocks: (1.00 TB/931 >> GiB) > > WD10EARS are "green" drives, 5400 rpm. They aren't designed exactly for > speed. Never used them, though. Oh.. The famous EARS drives. I missed this info in the start of the thread. Now, after this info, the whole thread is quite moot. The thing is, for these WD*EARS drivers, it is _vital_ to get proper alignment of all partitions and operations. They've 4Kb sectors physically but report 512bytes sectors to the OS. It is _essential_ to ensure all partitions are aligned to the 4Kb sectors. Be it LVM, raid-something, etc - each filesystem must start at a 4kb boundary at least, or else you'll see _dramatic_ write speed problems. So.. check the whole storage stack and ensure proper alignment everywhere. In particular, check that your partitions are not aligned to 63 sectors (512b), or starts at N+1 sector - the most problematic mode for these drives. And before anyone asks, no, these drives are actually very good. With proper alignment it works very fast for both reads and writes, despite it being 5400RPM. I have a 2Tb drive from these series (WD20EARS) - despite numerous claims that it does not work or works very slow with small files, it's quite fast, faster than many prev-gen 7200 drives. > No NCQ? Sil 3114 doesn't support of course. ICH7 (without letters) > doesn't do AHCI either IIRC. Yes, Sil 3114 does not support NCQ. But these drives does not have good NCQ implementation either - apparently the Read-Modify-Write logic has eaten NCQ which were traditionally good in recent WD drives. >> 9 Power_On_Hours 0x0032 091 091 000 Old_age >> Always - 7189 >> 193 Load_Cycle_Count 0x0032 164 164 000 Old_age Always >> - 109955 > > Hmm, some agressive power savings? May reduce performance significantly. > I'd disable all this "green" crap first. There's a utility (ms-dos based) to disable this feature for wd ears drives, on their website. >> Where it seems that WD simply says not to use these drives in a RAID. > > That smells like "don't use them in any serious application". No, this is about TLER. The "desktop" drives like this will try re-read data in case of error, and if that does not work the raid code will most likely declare the drive's dead and kick it off the array. Drives which are supposed to work in RAID config has configurable timeouts/retries, so that the RAID code will be able to take care of read errors. /mjt -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
