Date: Tue, 10 Aug 2010 19:44:48 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: hackers@freebsd.org, geom@freebsd.org Subject: Support for WD Advanced Format disks Message-ID: <86wrry1hwv.fsf@ds4.des.no>
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I'm looking into a clean, permanent solution for WD Green drives that use 4096-byte physical sectors. To summarize the information I've collected so far: - There are several types of WD Green disks. I am primarily interested in the 1+ TB models: EARS and EADS. - According to WD's own documentation, EARS disks are Advanced Format while EADS disks are not; furthermore, EARS disks have 64 MB cache while EADS disks have only 32 MB. - There is at least one source that provides model and serial numbers for two EADS disks that seem have the performance characteristics of an Advanced Format disk. One of them actually reports 4096-byte sectors, the other does not. I am not entirely certain that source is reliable. - Advanced Format disks should have a label that clearly describes them as such: http://media.bestofmicro.com/U/O/238272/original/Western-Digital-WD10EARS-t= op.jpg - I received an EADS disk and performed measurements which clearly show that it is *not* an Advanced Format disk. I had no trouble achieving 50 MBps with misaligned 8192-byte writes. Right now, I have two requests. The first is that people who have Advanced Format disks run a program I wrote that measures the performance of aligned and misaligned writes of different sizes. % svn co http://svn.freebsd.org/base/user/des/phybs % cd phybs % make % ./phybs -w /dev/adN Please note: - This test is *destructive*. Do not run it on a disk that contains data you care about; it *will* destroy them. - You can not run it on a file, but you *can* run it on a partition instead of the whole disk. You can even run it on a misaligned partition; the results will show by how much the partition is misaligned. - The test takes a long time. It took about half an hour on a WD20EADS connected by eSATA. It may take several hours on an Advanced Format disk. If you are impatient, try bumping MINSIZE to 1024 in phybs.c. The second request is for some kind soul to send me an EARS drive to play with; please contact me off-list if you're interested. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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