Does centos support advanced format disk ?

General support questions including new installations

Does centos support advanced format disk ?

Postby habernir » 2010/04/23 11:43:38

hi all i have a hard disk from WD and the name of model is WD10EARS

i just want to know if centos support it.

thanks a ahead , nir.
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Does centos support advanced format disk ?

Postby pschaff » 2010/04/23 12:33:52

Are you asking if CentOS supports the (unspecified) current format of the disk, or if CentOS can partition and format the disk?

If the former then please show the results of running "./getinfo.sh disk" as described in How to provide information about your system with the disk connected.

If the latter, then try using fdisk to partition and mkfs.ext3 to format and see if it works.
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Re: Does centos support advanced format disk ?

Postby habernir » 2010/04/23 14:22:57

i ask if centos not only it can partition and format this disk .
but if it can work with 4k sector drivers
because all the linux OS that isee (include fedora 12) can't work with this driver normaly because the performance of the disk is lost when you use it .
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Re: Does centos support advanced format disk ?

Postby pjwelsh » 2010/04/23 15:01:50

A quick google'n of "4k sector centos" yields a comment of:
http://centos.org/modules/newbb/viewtop ... 5&forum=37
and an issue of:
http://lists.centos.org/pipermail/cento ... 01701.html
Seems to be some possible "alignment" issues in general. Let us know what else you find, please.
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Re: Does centos support advanced format disk ?

Postby gulikoza » 2010/04/23 20:32:22

I have quite a few machines with advanced format disks. They indeed work a lot slower when not correctly formatted (raid sync works like 3 time slower). Maybe parted already aligns the partitions, but fdisk (which I mostly use) does not. While fdisk allows creating partitions on a specific sector, a bug will prevent creating partitions above 2^31 sectors plus it will nag about partitions not be cylinder aligned.
The solution is simple with a help of some math:
1. start every primary partition on a mod8 + 1 cylinder (1, 9, 17...)
2. end every primary partition (except the one before the extended p. which should end on mod8 + 1) on mod8 cylinder (32, 64...)
3. start extended partition and first logical drive on mod8 + 2 and end it (the logical p.) on mod8 +1 cylinder (ext. p. should obviously go to the end of the drive)
4. all other logical drives should start on mod8 +2 and end on mod8 +1 (this is because logical drives start 1 track inside the cylinder)
5. switch to sector view and fix first partition (move it to sector 1024 or 2048 or whatever windows does)
6. type p and confirm every partition starts on mod8 sector

That's it, all partitions perfectly aligned, no free space and full speed :-)

here's an example:
Code: Select all
/dev/sda1               1          32      256528   fd  Linux raid autodetect
/dev/sda2              33        4129    32909152+  fd  Linux raid autodetect
/dev/sda3            4130      182401  1431969840    5  Extended
/dev/sda5            4130       18209   113097568+  fd  Linux raid autodetect
/dev/sda6           18210       24609    51407968+  fd  Linux raid autodetect
/dev/sda7           24610       26657    16450528+  fd  Linux raid autodetect
/dev/sda8           26658       27681     8225248+  82  Linux swap / Solaris
/dev/sda9           27682      182401  1242788368+  fd  Linux raid autodetect

[Moderator edit: Added code tags to preserve formatting.]
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Re: Does centos support advanced format disk ?

Postby pschaff » 2010/04/23 20:53:16

Ain't teamwork great? :-D

Sounds like these ought to be labeled "Advanced [Administration Skills Required To] Format Disks". ;-)
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Re: Does centos support advanced format disk ?

Postby habernir » 2010/04/24 05:09:52

thanks all of you.
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Re: Does centos support advanced format disk ?

Postby gulikoza » 2010/04/25 16:44:29

It should be noted that this works as long as the filesystem begins at partition start. MD v0.90 metadata is at the end of partition, so you're safe there, but 1.1 is at the start of the partition so you need to make sure the real filesystem begins at a 4K aligned sector. The same goes for LVM and similar...and I guess filesystem should have atleast 4K (or multiple of) block size.
You can easily check if partition is properly aligned with hdparm -t. With unaligned partitions you get <30MB/s, properly aligned partitions should have >70MB/s at the beginning of the disk (falling to somewhere >40MB/s at the end of the disk).
Another solution I read somewhere is to change the disk geometry in advanced fdisk settings. Instead of 63 sectors/track you set 56 sectors/track for example. But I don't know how that would affect other OSes installed on the same disk...

But I am still wondering why there is such a performance hit. Obviously yes, for an unaligned read of 4K filesystem block the hard disk needs to read 2 sectors instead of 1. But HDs rarely read just one sector from the platters, they should read at least 8 at a time and put the contents into onboard cache. The same should apply for writes...But I guess it doesn't work like that :-)
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