[gentoo-user] 1-Terabyte drives - 4K sector sizes? -> bar performance so far

[Mark Knecht]

Hi,
   I got a WD 1T drive to use in a new machine for my dad. I didn't
pay a huge amount of attention to the technical details when I
purchased it other than it was SATA2, big, and the price was good.
Here's the NewEgg link:

http://www.newegg.com/Product/Product.aspx?Item=N82E16822136490

   I installed the drive, created some partitions and set off to put
ext3 on it using just mke2fs -j /dev/sda3. The partitions gets written
and everything works but when I started installing Gentoo on it I was
getting some HUGE delays at times, such as when unpacking
portage.latest.tar.bz. Basically the tar step would be rolling along
and then the drive would literally appear to stop for 1 minute before
proceeding. No CPU usage, the machine is alive in other terminals, but
anything directed at the disk just seems dead. Sticking my ear on the
drive it doesn't sound like the drive is doing anything.

   I was trying to determine what to do - I.e is this a bad drive, how
to return it, etc. - and started reading the reviews at NewEgg. One
guy using it with Linux had this to say:

<QUOTE>
4KB physical sectors: KNOW WHAT YOU'RE DOING!

Pros: Quiet, cool-running, big cache

Cons: The 4KB physical sectors are a problem waiting to happen. If you
misalign your partitions, disk performance can suffer. I ran
benchmarks in Linux using a number of filesystems, and I found that
with most filesystems, read performance and write performance with
large files didn't suffer with misaligned partitions, but writes of
many small files (unpacking a Linux kernel archive) could take several
times as long with misaligned partitions as with aligned partitions.
WD's advice about who needs to be concerned is overly simplistic,
IMHO, and it's flat-out wrong for Linux, although it's probably
accurate for 90% of buyers (those who run Windows or Mac OS and use
their standard partitioning tools). If you're not part of that 90%,
though, and if you don't fully understand this new technology and how
to handle it, buy a drive with conventional 512-byte sectors!
</QUOTE>

   Now, I don't mind getting a bit dirty learning to use this
correctly but I'm wondering what that means in a practical sense.
Reading the mke2fs man page the word 'sector' doesn't come up. It's my
understanding the Linux 'blocks' are groups of sectors. True? If the
disk must use 4K sectors then what - the smallest block has to be 4K
and I'm using 1 sector per block? It seems that ext3 doesn't support
anything larger than 4K?

   As a test I blew away all the partitions and made one huge 1
terabyte partition using ext3. I think tried untarring the portage
snapshot and then deleting the directory where I put it a bunch of
times. I get very different times each time I do this. untarring
varies from 6 minutes 24 seconds to 10 minutes 25 seconds. Removing
the directory varies from 3 seconds to 1 minute 22 seconds.

   Every time there is an apparent delay I just see the hard drive
light turned on solid. That said as far as I know if I wait for things
to complete the data is there but I haven't tested it extensively.

   Is this a bad drive or am I somehow using it incorrectly?

Thanks,
Mark


gandalf TestMount # time tar xjf /mnt/TestMount/portage-latest.tar.bz2
-C /mnt/TestMount/usr

real	6m24.736s
user	0m9.969s
sys	0m3.537s
gandalf TestMount # time rm -rf /mnt/TestMount/usr/

real	0m3.229s
user	0m0.110s
sys	0m1.809s
gandalf TestMount # mkdir usr
gandalf TestMount # time tar xjf /mnt/TestMount/portage-latest.tar.bz2
-C /mnt/TestMount/usr

real	7m50.193s
user	0m8.647s
sys	0m2.811s
gandalf TestMount # time rm -rf /mnt/TestMount/usr/

real	0m3.234s
user	0m0.119s
sys	0m1.792s
gandalf TestMount # mkdir usr
gandalf TestMount # time tar xjf /mnt/TestMount/portage-latest.tar.bz2
-C /mnt/TestMount/usr

real	10m25.926s
user	0m8.645s
sys	0m2.765s
gandalf TestMount # time rm -rf /mnt/TestMount/usr/

real	1m22.330s
user	0m0.124s
sys	0m1.810s
gandalf TestMount # mkdir usr
gandalf TestMount # time tar xjf /mnt/TestMount/portage-latest.tar.bz2
-C /mnt/TestMount/usr

real	8m12.307s
user	0m8.463s
sys	0m2.708s
gandalf TestMount # time rm -rf /mnt/TestMount/usr/

real	0m29.517s
user	0m0.114s
sys	0m1.810s
gandalf TestMount #




gandalf ~ # hdparm -tT /dev/sdb

/dev/sdb:
 Timing cached reads:   11362 MB in  2.00 seconds = 5684.46 MB/sec
 Timing buffered disk reads:  314 MB in  3.00 seconds = 104.64 MB/sec
gandalf ~ #