Converting ext3 to ext4 - results (Re: ext3 vs ext4)

Fri Feb 6 11:15:34 MST 2009

Bob Elzer wrote:
> This is informative, but I don't think the timing can be ruled accurate.
>   
Accurate as compared to what? I was just showing what it did on my 
system so that people could get a *rough* idea of how long it would take 
to convert a large partition.
> As I read your step, At first I thought tune2fs quit because it found
> something wrong, and told you to run e2fsck first.
>
> But further reading says, tune2fs makes a change, and then has e2fsck do all
> the grunt work converting.
>   
Yes the first fsck after the conversion is the long slow one.
> Your timings will be off, because the first e2fsck was doing all the hard
> work, it was finding all the checksums and recalculating them for ext4, and
> then writing them back to disk.
>   
Timings will be off of what? I guess you mean if you have less or more 
data it could take longer or shorter to convert (more inodes to muck 
around with).
> Thus you have all the I/O writes which adds a lot more time, then just
> reads. Writing is slow compared to just reading, and it's not a big block of
> writing, it lots of little
Yes.  My RAID is hardware RAID5.  For a single disk or striped array it 
would probably go a bit faster.
> It would have been nice to have an fsck before the tune2fs. 
>   
yeah I should have done that...I still have /raid1 to convert, which is 
exactly the same size.  I will do an fsck on that one first.

-Charles
>
> -----Original Message-----
> From: plug-discuss-bounces at lists.plug.phoenix.az.us
> [mailto:plug-discuss-bounces at lists.plug.phoenix.az.us] On Behalf Of Charles
> Jones
> Sent: Friday, February 06, 2009 8:45 AM
> To: Main PLUG discussion list
> Subject: Converting ext3 to ext4 - results (Re: ext3 vs ext4)
>
> Charles Jones wrote:
>   
>> I'm going to attempt a non-destructive conversion of a 2TB raid 
>> parition from ext3 to ext4. I will post the results :)
>>     
> Here's how it went. I did this on a system running Fedora Core 10:
>
> This is the partition I'm converting:
> # df -h /dev/sdc1
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sdc1             1.8T  844G  991G  47% /raid2
>
> I unmounted it, and ran the command (and used the "time" command to record
> how long it took):
> # time tune2fs -O extents,uninit_bg,dir_index /dev/sdc1 tune2fs 1.41.3
> (12-Oct-2008)
>
> Please run e2fsck on the filesystem.
>
> real    0m0.390s
> user    0m0.010s
> sys     0m0.012s
>
> Well that didn't take long at all.  Now for the fsck:
> # fsck -pf /dev/sdc1
> RAID2: Group descriptor 14903 checksum is invalid.  FIXED.
> RAID2: Group descriptor 14904 checksum is invalid.  FIXED.
> (a couple hundred of these quickly scrolled by) --^
> RAID2: Adding dirhash hint to filesystem.
>
> While it was running, I checked process listing and saw:
> root     12393  0.0  0.0   3984   696 pts/2    S+   05:59   0:00 fsck 
> -pf /dev/sdc1
> root     12394 66.8 14.1 223272 219832 pts/2   D+   05:59   1:04 
> fsck.ext3 -pf /dev/sdc1
> This worreid me a bit at first, as I thought it should be running
> /sbin/fsck.ext4 instead of fsck.ext3!
>
> It's done!
> RAID2: 350165/244203520 files (0.8% non-contiguous), 228806800/488382016
> blocks
> real    61m11.019s
> user    0m0.002s
> sys     0m0.011s
>
> Now lets fsck again, to verify that fsck's under ext4 take less time: 
> Before I run this second fsck I did notice that according to the drive
> access lights, the raid was busy doing "something", even though the initial
> fsck was complete.  What it is doing, I don't know - it's not defragging, as
> there is a seperate e4defrag tool...Hmm. Oh well lets run another fsck and
> see what happens:
> # time fsck -pf /dev/sdc1
> fsck 1.41.3 (12-Oct-2008)
> RAID2: 350165/244203520 files (0.8% non-contiguous), 228806800/488382016
> blocks
> real    35m19.580s
> user    1m48.430s
> sys     0m41.541s
>
> So fsck is a little over twice as fast now. I notice that after this fsck,
> there is no drive activity like there was the first time, so let's do it one
> more time:
>
> fsck 1.41.3 (12-Oct-2008)
> RAID2: 350165/244203520 files (0.8% non-contiguous), 228806800/488382016
> blocks
>
> real    34m51.145s
> user    1m47.481s
> sys     0m41.174s
>
> About the same time, as the second run.  It looks like FC10 doesn't have the
> e4defrag tool yet (I think requires new kernel).  When it is available I
> will do a run of it and post the results as well.
>
> # mount /dev/sdc1 /raid2
> # df -h /raid2
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sdc1             1.8T  844G  991G  47% /raid2
>
> # mount |grep raid2
> /dev/sdc1 on /raid2 type ext4 (rw)
>
> -Charles
>
>
>
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-- 
___________________________
Charles R. Jones II
IT Team Lead/Senior Systems Engineer
Cisco Learning Institute IT Dept
work: 602.343.1534  cell: 602.738.9993
charles.jones at ciscolearning.org

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