Why minor is still 8 bit?
I've understand that major and minor numbers for device is 8-bit size.
I've don't understand, WHY? In 2012!
(I've just have some discussion about 8-bit counter limitations in context of cloud computing. In middle of 2012!!!!)
But seriously, I've done some googling but found no answer why it still just 8 bit size. Is this some serious backward compatibility? Or just there is no one with itch strong enough?
Quoted 6 lines · George Shuklin
I've understand that major and minor numbers for device is 8-bit size.
I've don't understand, WHY? In 2012!
(I've just have some discussion about 8-bit counter limitations in context of cloud computing. In middle of 2012!!!!)
Yes, shocking. It's been several years and you are still using that buzzword; I mean, it's _so_ 2010... Should've moved on to whatever's in this year...
Incidentally, minors are 20 bit and majors are 12, but don't let that stand in the way of righteous indignation - what's mere facts when one is having discussions in context, presumably leveraging synergies all along...
Quoted 7 lines · Al Viro
Quoted 6 lines · George Shuklin
I've understand that major and minor numbers for device is 8-bit size.
I've don't understand, WHY? In 2012!
(I've just have some discussion about 8-bit counter limitations in context of cloud computing. In middle of 2012!!!!)
Quoted 8 lines
Yes, shocking. It's been several years and you are still using that buzzword; I mean, it's _so_ 2010... Should've moved on to whatever's in this year...
Incidentally, minors are 20 bit and majors are 12, but don't let that stand in the way of righteous indignation - what's mere facts when one is having discussions in context, presumably leveraging synergies all along...
Ok, thank you for information.
But question is almost same: can I have 30k active logical volumes on my single server, please?
Quoted 13 lines · George Shuklin
Quoted 11 lines · Al Viro
Quoted 6 lines · George Shuklin
I've understand that major and minor numbers for device is 8-bit size.
I've don't understand, WHY? In 2012!
(I've just have some discussion about 8-bit counter limitations in context of cloud computing. In middle of 2012!!!!)
Yes, shocking. It's been several years and you are still using that buzzword; I mean, it's _so_ 2010... Should've moved on to whatever's in this year...
Quoted 8 lines
Quoted 4 lines
Incidentally, minors are 20 bit and majors are 12, but don't let that stand in the way of righteous indignation - what's mere facts when one is having discussions in context, presumably leveraging synergies all along...
Ok, thank you for information.
But question is almost same: can I have 30k active logical volumes on my single server, please?
What are you trying to do, create a logical volume for every file? There are at least three separate technologies available that will solve whatever your problem is better than having 30,000 logical volumes. I don't have a clue what you think you're trying to accomplish and I am still willing to bet beers that you're bus is parked solidly on the wrong tracks.
Quoted 7 lines
Signature · 5 lines
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Quoted 19 lines · Casey Schaufler
Quoted 18 lines · George Shuklin
Quoted 7 lines · Al Viro
Quoted 6 lines · George Shuklin
I've understand that major and minor numbers for device is 8-bit size.
I've don't understand, WHY? In 2012!
(I've just have some discussion about 8-bit counter limitations in context of cloud computing. In middle of 2012!!!!)
Quoted 8 lines
Yes, shocking. It's been several years and you are still using that buzzword; I mean, it's _so_ 2010... Should've moved on to whatever's in this year...
Incidentally, minors are 20 bit and majors are 12, but don't let that stand in the way of righteous indignation - what's mere facts when one is having discussions in context, presumably leveraging synergies all along...
Ok, thank you for information.
Quoted 10 lines
Quoted 2 lines
But question is almost same: can I have 30k active logical volumes on my single server, please?
What are you trying to do, create a logical volume for every file? There are at least three separate technologies available that will solve whatever your problem is better than having 30,000 logical volumes. I don't have a clue what you think you're trying to accomplish and I am still willing to bet beers that you're bus is parked solidly on the wrong tracks.
Very simple sample: I'd like to create shared storage to publish volumes via ISCSI. ~60Tb of drives, ~2Gb average disk size = 30k disk images. Can I just create a bunch of LV and export them by iet or scst? Nope: There is a serious limit for amount of active LV per host. Yes, I can create filesystem, put images (as file) to that filesystem and publish them back, but why FS is needed to do such simple task?
Quoted 6 lines · George Shuklin
Very simple sample: I'd like to create shared storage to publish volumes via ISCSI. ~60Tb of drives, ~2Gb average disk size = 30k disk images. Can I just create a bunch of LV and export them by iet or scst? Nope:
There is a serious limit for amount of active LV per host. Yes, I can create filesystem, put images (as file) to that filesystem and publish them back, but why FS is needed to do such simple task?
You realize that with that many volumes, a logical volume manager *is* a filesystem, right?
-hpa
Quoted 11 lines · H. Peter Anvin
Quoted 6 lines · George Shuklin
Very simple sample: I'd like to create shared storage to publish volumes via ISCSI. ~60Tb of drives, ~2Gb average disk size = 30k disk images. Can I just create a bunch of LV and export them by iet or scst? Nope:
There is a serious limit for amount of active LV per host. Yes, I can create filesystem, put images (as file) to that filesystem and publish them back, but why FS is needed to do such simple task?You realize that with that many volumes, a logical volume manager *is* a filesystem, right?
-hpa
Well, I have nothing against filesystem with very small 'db-like' footprint: no directories, no attributes, extra-large allocation block, very fast initialization, no random file growth (very calm metadata without constant updating). If someone do have that type of FS (for disk images storage) - why not?
Anyway, using LVM to provide logical volumes to customers seems be fine (at least by name). But that limitation for minor is breaking whole idea.
I don't ask 'please fix', I'm just curious why so small?
Quoted 2 lines · George Shuklin
Anyway, using LVM to provide logical volumes to customers seems be fine (at least by name). But that limitation for minor is breaking whole idea.
man 8 vgcreate reads (in part):
-l, --maxlogicalvolumes MaxLogicalVolumes
Sets the maximum number of logical volumes allowed in this volume group. The setting can be changed with vgchange. For volume groups with metadata in lvm1 format, the limit and default value is 255. If the metadata uses lvm2 format, the default value is 0 which removes this restriction: there is then no limit.
Doesn't that option work for you (assuming you're not stuck on lvm1 format)? If not, where do things go wrong?
(Note that I never worry about this limit, since I never use more than a handful of logical volumes per volume group.)
Paul Bolle
Quoted 12 lines · Paul Bolle
Quoted 2 lines · George Shuklin
Anyway, using LVM to provide logical volumes to customers seems be fine (at least by name). But that limitation for minor is breaking whole idea.
man 8 vgcreate reads (in part):
-l, --maxlogicalvolumes MaxLogicalVolumes
Sets the maximum number of logical volumes allowed in this volume group. The setting can be changed with vgchange. For volume groups with metadata in lvm1 format, the limit and default value is 255. If the metadata uses lvm2 format, the default value is 0 which removes this restriction: there is then no limit.
Quoted 6 lines
Doesn't that option work for you (assuming you're not stuck on lvm1 format)? If not, where do things go wrong?
(Note that I never worry about this limit, since I never use more than a handful of logical volumes per volume group.)
This is a limitaiton of LMV itself. I'm talking about making those LV active (visible in system). When you trying to activate too much LV, you will get 'device io ctl failed' message.
Quoted 3 lines · George Shuklin
This is a limitaiton of LMV itself. I'm talking about making those LV active (visible in system). When you trying to activate too much LV, you will get 'device io ctl failed' message.
What is the exact text of that message? Where is it found (stderr, dmesg, ...)? Do you know what prints it (kernel, user space)? Do you run into this issue when trying to activate the 256th LV, or later, or earlier?
Paul Bolle
Quoted 4 lines · Paul Bolle
Quoted 3 lines · George Shuklin
This is a limitaiton of LMV itself. I'm talking about making those LV active (visible in system). When you trying to activate too much LV, you will get 'device io ctl failed' message.
Quoted 8 lines
What is the exact text of that message? Where is it found (stderr, dmesg, ...)? Do you know what prints it (kernel, user space)? Do you run into this issue when trying to activate the 256th LV, or later, or earlier?
Paul Bolle
Ooops, I was deeply wrong. Sorry, the problem was related to LVM behavior in 2.6.32-12-xs (XenServer kernel).