ufslogging vs. DiskSuite's trans device
As it turns out, as told to me by a Sun employee, the code for the translog
device in DiskSuite is the same exact code put into the logging feature in
the UFS kernel code. So:
Translog Device Pros:
1. Can be mirrored and therefor survive better from physical disk failure.
UFS logging Pros:
1. Less hastle in setting up (only requires a setting to be placed in the
/etc/vfstab for mount parameters)
2. Doesn't require it's own slice on the disk to store the logs
3. Can be applied to the root partition
4. Tighter connection to the kernel or at least less overhead than a
metatrans device
Though I am worried about the one thing going for the Translog device, I am
going to go with the UFS logging feature. I am going to use the logging
feature in conjunction with DiskSuite to mirror the disks which should
lessen the possibility of fs damage from a physical disk failure.
Here are the people, and their comments, who had something to contribute to
help me reach this decision:
-----------------------------------------------------
see www.sunworld.com for write up on ufslogging. The writer performed
some
basic benchmarks.
Please summarize your responses since I would like to know what everyone
else has to say.
Marcelino Mata <mmata@multiinc.com>
-----------------------------------------------------
The "configuration differences":
ufslogging:
vi /etc/vfstab & add "logging" to the options of the FS.
T do do it "on the run" (Normal caveat emptor & disclosures, although on
lightly loaded systems I've done it without hassles):
mount -o logging,remount /file/system
DiskSuite logging:
1) put the disks in the necessary RAID0, 1,0+1,5 etc.
ie. BOTH the data & the metatrans space set aside.
Typically the Metatrans would be a small mirror (Even three way
for the paranoid)
2) Then create the actual storage as another device with
the metatrans & and the "space" put together.
The architecture as I see it, is that the metatrans devices you
seperate the logs with the storage space, whereas the UFS logging
device they are the same.
The metatrans devices adds Way too much overhead for a simple
single disk setup (Like my laptop ;^) where I DO use a logging system
called ReiserFS running with Linux), while the UFS logging
might not be wants required with a biggish RAID5 setup where the
metatrans's log device might be better on mirrored disks on seperate
channels.
Hendrik Visage <hvisage@is.co.za>
-----------------------------------------------------
Steve,
Actually, this feature was available in Solaris 7. There's a nasty
reproducable bug in the UFS logging code in Solaris 8. If a user goes over
quota, whilst logging is enabled, the system panics. Settings the hard and
soft quotas the same fixes it.. but...
I run it on all of my Solaris 7 machines. The performance isn't too bad
after
it's been done. I'm using it because we can't spend the bucks on a Veritas
solution. I would NEVER use DiskSuite for this. Too many chances
corruption
can happen (ie lose your metadb and try to recover your data ;) ). I trust
the OS to handle this best. If you can't afford Veritas, this is not a bad
solution.
Hope that helps,
--Thomas
PS: Certified on Solaris 2.6 ;)
"Thomas Wardman" <wardtj@uleth.ca>
-----------------------------------------------------
Well, I'm not "Solaris 8 certified", but I've been poking at this issue for
a few months now. Here's what I've learned so far:
The UFS logging function was made available in Solaris 7, and continued in
Solaris 8. The biggest difference I've been able to find so far is that
the
filesystem log is kept within the filesystem when using the "logging"
option
to mount_ufs, while DiskSuite enables/requires a separate partition or
metadevice for the filesystem log. We are really talking about some
interesting perspectives on disk maintenance and failure modes when
considering the scenarios where this could make a difference. As far as
I've been able to tell, the operation of the UFS log seems the same whether
you use the OS function, or the DiskSuite option. I have recently taken to
building servers with all filesystems mirrored through DiskSuite, and using
DiskSuite to do the logging for everything but the root filesystem. Since
DiskSuite will not allow logging the root filesystem, that one has to use
the OS logging option to mount_ufs in /etc/vfstab. It is my
hope/understanding that this will give me a configuration that is much more
resistant to filesystem corruption in the event of a crash, and
boots/recovers faster as well.
My $.02 worth.
Ronald Loftin <reloftin@syr.edu>
-----------------------------------------------------
On Mon, 2 Oct 2000SGauthier@domainpharma.com wrote:
> Anyone have any insight on which is better?
>
> In Solaris 8, there is a new feature to the base OS ufs feature list:
> ufslogging.
(Slight correction: it is apparently there in Solaris 7, too.)
> As far as I knew, you could only get this feature by using DiskSuite or
> Veratos before Solaris 8.
>
> Anyone educated enough (i.e. Solaris 8 certified) to suggest one vs the
> other?
I don't know. But your summary will be of interest to me (and, I suspect,
to various other folk).
One advantage of UFS logging is that it is easier to administer: simply
set the option, rather than having to configure trans devices etc.
David Lee <T.D.Lee@durham.ac.uk>
-----------------------------------------------------
Well I am not Solaris Certified, but I can tell you that the UFS logging is
better. If you do use the metatrans device, you need to mirror it because
it
is corruption prone. Logging was added as a feature starting in Solaris 7.
check this site ( its currently down ) for more details. There is a
comparison between vxvm and disksuite.
http://www.eng.auburn.edu/pub/mail-lists/ssastuff/
Regards,
--Buddy
Buddy Lumpkin <BLumpkin@echarge.com>
-----------------------------------------------------
On Mon, 2 Oct 2000SGauthier@domainpharma.com wrote:
> Anyone have any insight on which is better?
>
> In Solaris 8, there is a new feature to the base OS ufs feature list:
> ufslogging.
>
> As far as I knew, you could only get this feature by using DiskSuite or
> Veratos before Solaris 8.
>
> Anyone educated enough (i.e. Solaris 8 certified) to suggest one vs the
> other?
Bad Steve, Bad, Bad Steve! You have'nt been reading your www.sunworld.com,
now have you? :) Checkout the article entitled "Why aren't you logging"!!
Conclusion, enable logging on all your Sol 8 mounts. Consider noatime for
/var.
Al Hopper <al@logical-approach.com>
-----------------------------------------------------
Hi Steve,
Additionally, ufslogging is also available in Solaris 7. I've been using
it
with Solaris 7 for about 2 years now.
I can't draw comparisons with you against Veritas though, I'm only new to
Veritas.
Regards,
"Clift, Justin" <JClift@powercor.com.au>
-----------------------------------------------------
Ufslogging in Solaris 8 is the same code that previously came with
Disksuite, so there is no difference between these two.
In my experience this works ok and I would recommend it, especially
for large filesystems, so you don't have to run fsck in case of
system crash etc...
Petri Kallberg - Sun Finland - <kallu@helsinki.Finland.Sun.COM>
-----------------------------------------------------
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UNIX/VMS/Macintosh Systems Administrator 10 Maguire Road
PHONE: (781) 778 - 3953 Lexington, MA 02421
FAX: (781) 778 - 3800 E-mail:sgauthier@domainpharma.com
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