Mirroring
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
Thanks,
Chris Anderson
Quoted 3 lines · Chris Anderson
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
It's more like one partition or logical volume mirrored against another one (not necessarily disks - you seem to be familiar with Novell). LVM can't do this. Use MD.
Signature · 2 lines
If you sit down at a poker game and don't see a sucker, get up. You're the sucker.
Quoted 8 lines · Harald Milz
Quoted 3 lines · Chris Anderson
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
It's more like one partition or logical volume mirrored against another one (not necessarily disks - you seem to be familiar with Novell). LVM can't do this. Use MD.
I know veritas. It has a SubDisk, Plex Volume setup. A subdisk is part of a disk and one or more subdisk make a Plex and one or more plexes make a volume. And a volume can be used as a mount point or whatever.
So if a disk goes bad only plexes with use a subdisk from that disk are down. And if a volume has two plex only one need to be up to run. Later the plex can be re-joined back to the volume and the data is synched back to the other plex.
In a nut shell what happens when one disk goes down with LVM? Can it be setup to keep the volume up and alive and run and if so what is the best way?
Quoted 5 lines
--
If you sit down at a poker game and don't see a sucker, get up. You're the sucker.
What you're asking is can LVM be used in conjunction with MD, and is this the correct solution or is LVM/MD going to merge or LVM duplicate MD's work??
I'd like those answers too!!!!
Quoted 29 lines · Chris Anderson
Quoted 8 lines · Harald Milz
Quoted 3 lines · Chris Anderson
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
It's more like one partition or logical volume mirrored against another one (not necessarily disks - you seem to be familiar with Novell). LVM can't do this. Use MD.
I know veritas. It has a SubDisk, Plex Volume setup. A subdisk is part of a disk and one or more subdisk make a Plex and one or more plexes make a volume. And a volume can be used as a mount point or whatever.
So if a disk goes bad only plexes with use a subdisk from that disk are down. And if a volume has two plex only one need to be up to run. Later the plex can be re-joined back to the volume and the data is synched back to the other plex.
In a nut shell what happens when one disk goes down with LVM? Can it be setup to keep the volume up and alive and run and if so what is the best way?
Quoted 5 lines
--
If you sit down at a poker game and don't see a sucker, get up. You're the sucker.
Quoted 3 lines · A James Lewis
What you're asking is can LVM be used in conjunction with MD, and is this the correct solution or is LVM/MD going to merge or LVM duplicate MD's work??
What is MD and where can I get it? And why would we not want LVM to do this? That is what a logical volumne manager is for? Yes?
Please note that it a month veritas will be out for linux. It will have these options, I think maybe we should think about what options they have and maybe make some plans for lvm. I say "we" because I would love to help were I could.
Quoted 35 lines
I'd like those answers too!!!!
Quoted 29 lines · Chris Anderson
Quoted 8 lines · Harald Milz
Quoted 3 lines · Chris Anderson
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
It's more like one partition or logical volume mirrored against another one (not necessarily disks - you seem to be familiar with Novell). LVM can't do this. Use MD.
I know veritas. It has a SubDisk, Plex Volume setup. A subdisk is part of a disk and one or more subdisk make a Plex and one or more plexes make a volume. And a volume can be used as a mount point or whatever.
So if a disk goes bad only plexes with use a subdisk from that disk are down. And if a volume has two plex only one need to be up to run. Later the plex can be re-joined back to the volume and the data is synched back to the other plex.
In a nut shell what happens when one disk goes down with LVM? Can it be setup to keep the volume up and alive and run and if so what is the best way?
Quoted 5 lines
--
If you sit down at a poker game and don't see a sucker, get up. You're the sucker.
Quoted 2 lines · Chris Anderson
What is MD and where can I get it? And why would we not want LVM to do this? That is what a logical volumne manager is for? Yes?
uhm...
Quoted 1 line
X-Mailer: Mozilla 4.7 [en] (X11; I; Linux 2.2.14 i686)
look at http://www.redhat.com/~mingo/raid-2.2.14-B1 for the patch and http://ostenfeld.dk/~jakob/Software-RAID.HOWTO for the docs
i believe raid is being merged in the very latest 2.3.x kernel
Quoted 1 line
Please note that it a month veritas will be out for linux. It will have these
i never believed in schedules :)
L.
Signature · 2 lines
Luca Berra -- [email protected] Communication Media & Services S.r.l.
Hi, I am relatively new to this list, and to Linux LVM, but when Heinz was at the U of MN last month, I asked this very question, and Heinz's response was that there are not currently plans for mirroring LEs to PEs precisely because this functionality is provided by md or RAID hardware.
MD is the kernel RAID facility, and provides mirroring (RAID 1) in kernel software. It provides several other RAID versions as well.
Heinz, habe ich es richtig verstanden?
-Chris McKinley
Quoted 41 lines · A James Lewis
What you're asking is can LVM be used in conjunction with MD, and is this the correct solution or is LVM/MD going to merge or LVM duplicate MD's work??
I'd like those answers too!!!!
Quoted 29 lines · Chris Anderson
Quoted 8 lines · Harald Milz
Quoted 3 lines · Chris Anderson
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
It's more like one partition or logical volume mirrored against another one (not necessarily disks - you seem to be familiar with Novell). LVM can't do this. Use MD.
I know veritas. It has a SubDisk, Plex Volume setup. A subdisk is part of a disk and one or more subdisk make a Plex and one or more plexes make a volume. And a volume can be used as a mount point or whatever.
So if a disk goes bad only plexes with use a subdisk from that disk are down. And if a volume has two plex only one need to be up to run. Later the plex can be re-joined back to the volume and the data is synched back to the other plex.
In a nut shell what happens when one disk goes down with LVM? Can it be setup to keep the volume up and alive and run and if so what is the best way?
Quoted 5 lines
--
If you sit down at a poker game and don't see a sucker, get up. You're the sucker.
Quoted 4 lines
Hi, I am relatively new to this list, and to Linux LVM, but when Heinz was at the U of MN last month, I asked this very question, and Heinz's response was that there are not currently plans for mirroring LEs to PEs precisely because this functionality is provided by md or RAID hardware.
Yes.
The LVM covers the dynamic allocation of storage. Either RAID soft- or hardware covers the redundancy.
IMO you get a much simpler systemarchitecture this way which is much more reliable for day to day production.
IOW: it saves your money.
Quoted 3 lines
MD is the kernel RAID facility, and provides mirroring (RAID 1) in kernel software. It provides several other RAID versions as well.
Exactly. RAID4+5 are the other ones.
Quoted 2 lines
Heinz, habe ich es richtig verstanden?
Ja 8)
Heinz
Quoted 11 lines
-Chris McKinley
Quoted 6 lines · A James Lewis
What you're asking is can LVM be used in conjunction with MD, and is this the correct solution or is LVM/MD going to merge or LVM duplicate MD's work??
I'd like those answers too!!!!
No merge activities so far.
Quoted 36 lines
Quoted 35 lines · Chris Anderson
Quoted 30 lines
Quoted 8 lines · Harald Milz
Quoted 3 lines · Chris Anderson
I have looked through the doc and I see that LVM stripes but how do you setup a true mirror? One hard dive mirrored to another hard drive (1 to 1).
It's more like one partition or logical volume mirrored against another one (not necessarily disks - you seem to be familiar with Novell). LVM can't do this. Use MD.
I know veritas. It has a SubDisk, Plex Volume setup. A subdisk is part of a disk and one or more subdisk make a Plex and one or more plexes make a volume. And a volume can be used as a mount point or whatever.
So if a disk goes bad only plexes with use a subdisk from that disk are down. And if a volume has two plex only one need to be up to run. Later the plex can be re-joined back to the volume and the data is synched back to the other plex.
In a nut shell what happens when one disk goes down with LVM? Can it be setup to keep the volume up and alive and run and if so what is the best way?
Quoted 5 lines
--
If you sit down at a poker game and don't see a sucker, get up. You're the sucker.
Signature · 11 lines
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Systemmanagement CS-TS T-Nova
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Heinz Mauelshagen Otto-Roehm-Strasse 71c
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=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-Quoted 5 lines · Heinz Mauelshagen
Quoted 4 lines
Hi, I am relatively new to this list, and to Linux LVM, but when Heinz was at the U of MN last month, I asked this very question, and Heinz's response was that there are not currently plans for mirroring LEs to PEs precisely because this functionality is provided by md or RAID hardware.
Quoted 8 lines
Yes.
The LVM covers the dynamic allocation of storage. Either RAID soft- or hardware covers the redundancy.IMO you get a much simpler systemarchitecture this way which is much more reliable for day to day production.
IOW: it saves your money.
perhaps...but it makes it impossible, if I've understood this architecture, to use a floating mirror for live backups.
i.e., set up 3 10 gb partitions "a" "b" and "c", and one 10 gb spare "d"
attach "d" as a mirror of "a", wait for sync, detach, backup "d" attach "d" as a mirror of "b", wait for sync, detach, backup "d" etc.
(for redundant situations, "a" "b" and "c" may already be mirrored so you're attaching the floater as an _additional_ mirror)
maybe the application for such usage is not widespread enough, though...
Quoted 8 lines
perhaps...but it makes it impossible, if I've understood this architecture, to use a floating mirror for live backups.
i.e., set up 3 10 gb partitions "a" "b" and "c", and one 10 gb spare "d"
attach "d" as a mirror of "a", wait for sync, detach, backup "d" attach "d" as a mirror of "b", wait for sync, detach, backup "d" etc.
AFAICS you can do the same with LVM snapshots (not fully working yet). Either create an LVM snapshot and backup the snapshot directly or copy the snapshot to an extra lvol.
IMHO you get the same result by using a different machanism.
Just a thought
Michael
--
Michael Marxmeier Marxmeier Software AG E-Mail: [email protected] Besenbruchstrasse 9 Phone : +49 202 2431440 42285 Wuppertal, Germany Fax : +49 202 2431420 http://www.msede.com/
Quoted 4 lines · A James Lewis
What you're asking is can LVM be used in conjunction with MD, and is this the correct solution or is LVM/MD going to merge or LVM duplicate MD's work??
Yes. LVM on MD works great. I have a 4 disk
RAID 5 that I run LVM on to chop up into more managable chunks. 40GB for a single FS is a bit excessive. I do this with the new raid 0.90. I've never tried it with the kernel standard raid, but I think I've seem success reports.
Applying the LVM patch and the raid0.90 patch
gets you some errors in ll_rw_block.c, but if you know C, you can pretty much figure out how to patch it by hand. If anyone wants to do this and needs help with the patches, I'd be happy to help.
LVM on top of MD is great. I get redundancy
and managability.
Brian