28 Aug
2012
28 Aug
'12
1:24 a.m.
Hi All,
I'm currently getting our DR system fine tuned at work, and as part of this I would
like some software to take images of some of our larger Linux servers (RHCE 5 & 6)
similar to how programs like Shadow Protect does for Windoze based systems, in other words
while the system is live. Some of these server have up to 6TB of data stored on them and
as you could appreciate, downing the server to run something like Clonezilla would take
far too long to be practical. I would also like to be able to schedule these snapshots,
say once a week.
TIA,
Chris
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28 Aug
28 Aug
1:49 a.m.
Hi Chris,
Perhaps "fsarchiver" may do the job? It does backup live systems.
Cheer
Daniel
On 28/08/12 11:24, Christopher M. Bailey wrote:
Hi All,
I'm currently getting our DR system fine tuned at work, and as part of
this I would like some software to take images of some of our larger
Linux servers (RHCE 5 & 6) similar to how programs like Shadow Protect
does for Windoze based systems, in other words while the system is
live. Some of these server have up to 6TB of data stored on them and
as you could appreciate, downing the server to run something like
Clonezilla would take far too long to be practical. I would also like
to be able to schedule these snapshots, say once a week.
TIA,
Chris
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This message has been scanned for viruses and
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2:15 a.m.
Daniel Jitnah <djitnah(a)greenwareit.com.au> wrote:
Perhaps "fsarchiver" may do the job? It does
backup live systems.
There are also dump utilities for various file systems, for example
xfsdump/xfsrestore for XFS, and probably similar tools for EXT2/3/4.
If you're using lvm, you could take an lvm snapshot and then create a backup
of that. I'll leave it to the lvm experts to comment in detail.
3:03 a.m.
On Tue, 28 Aug 2012, Daniel Jitnah <djitnah(a)greenwareit.com.au> wrote:
Perhaps "fsarchiver" may do the job? It does
backup live systems.
http://www.fsarchiver.org/Main_Page
According to the above web page it merely does file level access to the data.
So if you have a live database or something similar then you WILL get corrupt
data.
On Tue, 28 Aug 2012, Jason White <jason(a)jasonjgw.net> wrote:
There are also dump utilities for various file
systems, for example
xfsdump/xfsrestore for XFS, and probably similar tools for EXT2/3/4.
I believe that they all have the same issues.
If you're using lvm, you could take an lvm
snapshot and then create a
backup of that. I'll leave it to the lvm experts to comment in detail.
To make a backup of a live system you need to snapshot ALL inter-related
filesystems at the same time. If for example you have a database store and
it's log files on separate filesystems then it may be theoretically impossible
to create snapshots in a way that guarantees no data loss on restore (based on
previous discussion on this list about database logging).
If there are no cross-filesystem data dependencies then LVM snapshots will work
well. As will BTRFS and ZFS snapshots. But for RHEL there is no reasonable
option of ZFS for BTRFS Red Hat say:
https://access.redhat.com/knowledge/docs/en-
US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/ch-btrfs.html
# Btrfs is not a production quality file system at this point. With Red Hat
# Enterprise Linux 6 it is at a tech preview stage
So for a RHEL user who wants live snapshots of databases it seems that any
good option would involve using LVM and keeping all correlated data on one
filesystem.
http://etbe.coker.com.au/2012/08/08/hard-drives-backup/
For someone who's not using a Red Hat supported environment ZFS seems to be a
necessary part of an ideal solution at this time, see my above blog post for
details.
For backing up the boot partition etc (the other part of the original request)
I'm not sure what is the best option on Linux and so far none of the answers
have addressed this.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
3:31 a.m.
On 28/08/12 13:03, Russell Coker wrote:
# Btrfs is not a production quality file system at
this point. With Red Hat
# Enterprise Linux 6 it is at a tech preview stage
I would argue that is the case for btrfs in any distro as the upstream
code in the mainline kernel is still marked experimental.
cheers,
Chris
--
Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC
3:33 a.m.
[oops - missed this bit previously]
On 28/08/12 13:03, Russell Coker wrote:
According to the above web page it merely does file
level access to the data.
So if you have a live database or something similar then you WILL get corrupt
data.
I would have thought this would be a risk for any mechanism that doesn't
get the database to dump its state in a consistent manner, whether it be
file level, filesystem level or disk level snapshots.
cheers,
Chris
--
Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC
3:56 a.m.
On Tue, 28 Aug 2012, Chris Samuel <chris(a)csamuel.org> wrote:
Why wouldn't filesystem level snapshots allow a consistent database backup if a
single filesystem is used for all tables and logs?
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
According to
the above web page it merely does file level access to the
data. So if you have a live database or something similar then you
WILL get corrupt data.
I would have thought this would be a risk for any mechanism that doesn't
get the database to dump its state in a consistent manner, whether it be
file level, filesystem level or disk level snapshots. 
29 Aug
29 Aug
4:45 a.m.
Hi All,
On 28/08/2012 11:24 AM, Christopher M. Bailey wrote:
I'm currently getting our DR system fine tuned at
work, and as part of
this I would like some software to take images of some of our larger
Linux servers (RHCE 5 & 6) similar to how programs like Shadow Protect
does for Windoze based systems, in other words while the system is
live. Some of these server have up to 6TB of data stored on them and as
you could appreciate, downing the server to run something like
Clonezilla would take far too long to be practical. I would also like
to be able to schedule these snapshots, say once a week.
Unless I am mistaken, all Shadow Protect does is create snapshot of the
filesystem at a point in time. No different to taking an LVM snapshot.
If at that point in time there are processes still with open files and
data in memory, then you have every risk of corruption and lack of a
suitable backup.
Non-database files are less likely to be a problem with rsync type
backups -- I use rsnapshot for these. But database tables need to be
fully consistent and so a short "freeze" will be required to be sure
that everything is good.
Lots to consider, are you using Xen, KVM or any other virtualization in
your setup? Are you using RAID1 and can you shutdown briefly,
disconnect a drive from RAID1 (preferably with 3 or more RAID members in
normal operation). LVM snapshots are also a good option. I shutdown
entire VM's just long enough to snapshot all file systems, then restart
the VM and proceed with backing up off the snapshots.
How many and what type of disks make up the 6TB ? How are they set up?
Using dump tools is likely to cause problems unless the dump is of a
consistent snapshot. Linus sees dump of running file systems as
"stupid" because you can never be sure that the OS has written
everything to disk, so you cannot guarantee the state -- unless of
course it is an unmounted snapshot area that you are dumping, you will
not get a "proper" backup.
Oracle has been claiming production ready BTRFS, but I don't know anyone
whom really believes that, I mean *really* believes. Using BTRFS today
has it's own risks.
With 6TB of data, you really should have RAID1 protection at least and
LVM snspshots with perhaps the rsnapshot tool and/or dumps (again of
non-running file systems). I would say that you need a standby server
to rsync to as well, a DR server, best at a separate DR site if possible.
Cheers
--
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AndrewM
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6:24 a.m.
Andrew McGlashan wrote:
Non-database files are less likely to be a problem
with rsync type
backups -- I use rsnapshot for these. But database tables need to
be fully consistent and so a short "freeze" will be required to be
sure that everything is good.
The other way you can do it, is tell rsync to exclude the "real"
database files, and don't worry if they're incoherent, because you
have a daily cron job that tells the db to make a coherent dump of
itself to a local file, which rsync will back up.
2:23 p.m.
On 29/08/2012 4:24 PM, Trent W. Buck wrote:
Andrew McGlashan wrote:
Yes I use .rsync-filter files for that purpose, exclusion.
Cheers
A.
Non-database files are less likely to be a
problem with rsync type
backups -- I use rsnapshot for these. But database tables need to
be fully consistent and so a short "freeze" will be required to be
sure that everything is good.
The other way you can do it, is tell rsync to exclude the "real"
database files, and don't worry if they're incoherent, because you
have a daily cron job that tells the db to make a coherent dump of
itself to a local file, which rsync will back up.
7:35 a.m.
On Wed, 29 Aug 2012, Andrew McGlashan <andrew.mcglashan(a)affinityvision.com.au>
wrote:
Unless I am mistaken, all Shadow Protect does is
create snapshot of the
filesystem at a point in time. No different to taking an LVM snapshot.
AFAIK the only ways of making a snapshot on Linux are LVM (which is supported
everywhere - including RHEL), BTRFS (experimental everywhere except Oracle and
"tech preview" in RHEL), and ZFS (reliable but not supported in RHEL).
Unless Shadow Protect uses LVM snapshots I don't think it can do what you
claim.
If at that point in time there are processes still
with open files and
data in memory, then you have every risk of corruption and lack of a
suitable backup.
No, if you have all MySQL data on a single filesystem then you should be safe
with an LVM snapshot.
Lots to consider, are you using Xen, KVM or any other
virtualization in
your setup? Are you using RAID1 and can you shutdown briefly,
disconnect a drive from RAID1 (preferably with 3 or more RAID members in
normal operation). LVM snapshots are also a good option. I shutdown
entire VM's just long enough to snapshot all file systems, then restart
the VM and proceed with backing up off the snapshots.
How many and what type of disks make up the 6TB ? How are they set up?
6TB wouldn't be a RAID-1.
On Wed, 29 Aug 2012, "Trent W. Buck" <trentbuck(a)gmail.com> wrote:
The other way you can do it, is tell rsync to exclude
the "real"
database files, and don't worry if they're incoherent, because you
have a daily cron job that tells the db to make a coherent dump of
itself to a local file, which rsync will back up.
That is very good for a small database. For my blog I have a cron job which
dumps the database and another cron job on a workstation to copy the daily
dump file. Then the directory full of daily dump files is part of the
workstation backup. This is for a dump file that's 5.6M compressed.
When you have a big database (or even a database that's a few gigs in size)
you don't necessarily want to wait for a dump to be loaded before going live.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
10:41 a.m.
Russell Coker wrote:
AFAIK the only ways of making a snapshot on Linux are
LVM (which is
supported everywhere - including RHEL), BTRFS (experimental
everywhere except Oracle and "tech preview" in RHEL), and ZFS
(reliable but not supported in RHEL).
Nitpick: doesn't linux support an alternative to LVM (EVMS?) that
nobody uses? That probably has a snapshot facility, too.
11:54 a.m.
On Wed, 29 Aug 2012, "Trent W. Buck" <trentbuck(a)gmail.com> wrote:
Nitpick: doesn't linux support an alternative to
LVM (EVMS?) that
nobody uses? That probably has a snapshot facility, too.
http://en.wikipedia.org/wiki/Enterprise_Volume_Management_System
EVMS is long dead and the management tools were migrated to using LVM2 kernel
code.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
30 Aug
30 Aug
12:58 a.m.
On Wed, 29 Aug 2012, Russell Coker wrote:
When you have a big database (or even a database
that's a few gigs in size)
you don't necessarily want to wait for a dump to be loaded before going live.
In these cases a cold standby and replication may do the trick for you.
With MySQL it is not that hard to set up.
Regards
Peter
29 Aug
29 Aug
11:57 a.m.
Hi All,
On 28/08/2012 11:24 AM, Christopher M. Bailey wrote:
Unlikely. Windows VSS is _very_ good. Firstly, it allows snapshot sets to be taken
atomically across multiple volumes (think /var/db_data and /var/db_logs) ensuring true
crash-consistent snapshots. If /var/db_data and /var/db_logs were on separate LVM volumes
under Linux, all bets are off.
Secondly, VSS is tightly integrated with the OS. Any decent database or other application
will provide a VSS writer which tells the backup application exactly how to back up the
data for the database. To give an example, for Windows 2003 and older, when a VSS snapshot
is taken the registry files are dumped to a different location and instructions are
provided to the backup application to back the files up from there as if they were really
in C:\Windows\System32\config. For an MSSQL differential backup, the backup application is
told exactly which file fragments (eg offset 1234 length 456) have changed since the full
backup was taken, so that only those need to be backed up. For Exchange, log truncation
etc is handled automatically.
Even without fancy instructions required, the VSS snapshot process gives applications a
chance to ensure application level consistency.
Sorry to sound like a Microsoft shill, but I've contributed code to the Bacula project
to do all the above stuff so I can appreciate the differences.
James
I'm currently getting our DR system fine
tuned at work, and as part of
this I would like some software to take images of some of our larger
Linux servers (RHCE 5 & 6) similar to how programs like Shadow Protect
does for Windoze based systems, in other words while the system is
live. Some of these server have up to 6TB of data stored on them and
as you could appreciate, downing the server to run something like
Clonezilla would take far too long to be practical. I would also like
to be able to schedule these snapshots, say once a week.
Unless I am mistaken, all Shadow Protect does is create snapshot of the
filesystem at a point in time. No different to taking an LVM snapshot.
If at that point in time there are processes still with open files and data in
memory, then you have every risk of corruption and lack of a suitable
backup.
2:29 p.m.
On 29/08/2012 9:57 PM, James Harper wrote:
Unlikely. Windows VSS is _very_ good. Firstly, it
allows snapshot sets to be taken atomically across multiple volumes (think /var/db_data
and /var/db_logs) ensuring true crash-consistent snapshots. If /var/db_data and
/var/db_logs were on separate LVM volumes under Linux, all bets are off.
Secondly, VSS is tightly integrated with the OS. Any decent database or other application
will provide a VSS writer which tells the backup application exactly how to back up the
data for the database. To give an example, for Windows 2003 and older, when a VSS snapshot
is taken the registry files are dumped to a different location and instructions are
provided to the backup application to back the files up from there as if they were really
in C:\Windows\System32\config. For an MSSQL differential backup, the backup application is
told exactly which file fragments (eg offset 1234 length 456) have changed since the full
backup was taken, so that only those need to be backed up. For Exchange, log truncation
etc is handled automatically.
Even without fancy instructions required, the VSS snapshot process gives applications a
chance to ensure application level consistency.
Sorry to sound like a Microsoft shill, but I've contributed code to the Bacula
project to do all the above stuff so I can appreciate the differences.
Yes, I have to agree that VSS is seriously good, but you still need
application aware programs to be sure that the backup is fully
consistent. MSSQL might be fine without special consideration, but just
because it is a Windows box, doesn't mean it needs to have a native
database.
Oh and to Russell... 6TB could easily be multiple RAID1 volumes, who
knows, it could be anything -- hence why I asked and didn't ass-u-me ... ;)
There is always more than one way to skin a cat, so to speak and usually
quite a number of ways.
Cheers
A.
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15 comments
9 participants
participants (9)
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Andrew McGlashan -
Chris Samuel -
Christopher M. Bailey -
Daniel Jitnah -
James Harper -
Jason White -
Peter Ross -
Russell Coker -
Trent W. Buck