aspgasd@cid.aes.doe.CA (Alain St-Denis) (10/06/90)
We are planning to upgrade to IRIX 3.3.1 very soon now and we want to use the logical volume feature. So I read all I found about it in the admin guide and the reference man. One question arose for which I couldn't find any answer: Suppose a logical volume that contains two disks. What would be the procedure to restore a logical volume in the event of a disk failure? Suppose we don't use disk stripping because we're extending our current file systems using some other disks that are already partitionned with strange sizes. If it's a RTFM issue, please point the right manual to me. Thank you all. -- Alain St-Denis Centre informatique de Dorval Environnement Canada astdenis@cid.aes.doe.CA
daveh@xtenk.asd.sgi.com (David A Higgen) (10/06/90)
In article <1990Oct5.200050.28273@cid.aes.doe.CA>, aspgasd@cid.aes.doe.CA (Alain St-Denis) writes: > > We are planning to upgrade to IRIX 3.3.1 very soon now and we want to use > the logical volume feature. So I read all I found about it in the admin > guide and the reference man. One question arose for which I couldn't find > any answer: Suppose a logical volume that contains two disks. What would > be the procedure to restore a logical volume in the event of a disk > failure? There is really no "special" way to restore a logical volume if a component disk crashes. You have to regard the whole volume as effectively one disk, and proceed as you would if a regular disk crashes: repair the disk, make a new filesystem, and restore from backups. In the logical volume case, there would need to be one additional step before the mkfs: running lvck to restore the logical volume label on the repaired disk (to re-identify it as part of the logical volume). Dave Higgen (daveh@xtenk.asd.sgi.com)
aspgasd@cidsv01.cid.aes.doe.CA (Alain St-Denis) (10/22/90)
Is there a manual that comes with the 3.3 distribution that explains the implemantation of the logical volumes (other than System Administrator's Guide)? I would like to know how the disk stripping works for SGI machines. In fact, I would like to know everything there is to say about logical volumes. For example, how efficiently will a file system extended with growfs allocate file space. Thanx. Alain St-Denis Centre informatique de Dorval Environnement Canada astdenis@cid.aes.doe.CA (514) 421-4697
aspgasd@cidsv01.cid.aes.doe.CA (Alain St-Denis) (10/23/90)
Is there a manual that explains all there is to know about logical volumes? I already read the System Administrator's Guide. I would like to know how the stripping is implemented and also how the file space is allocated on a logical volume extended with growfs. Thanx. Alain St-Denis Centre informatique de Dorval Environnement Canada astdenis@cid.aes.doe.CA (514) 421-4697
daveh@xtenk.asd.sgi.com (David A Higgen) (10/23/90)
In article <1990Oct22.155144.13535@cid.aes.doe.CA>, aspgasd@cidsv01.cid.aes.doe.CA (Alain St-Denis) writes: > Is there a manual that comes with the 3.3 distribution that explains the > implemantation of the logical volumes (other than System Administrator's > Guide)? Not as far as I know. But the System Administrator's Guide contains a fair amount of info, including some step-by-step setup examples. > I would like to know how the disk stripping works for SGI machines. In > fact, I would like to know everything there is to say about logical > volumes. Yikes! *Everything* there is to say!? Not a modest request! 8-) If you have specific questions I'll be happy to try to answer them, I am the architect & implementor of our logical volumes. > For example, how efficiently will a file system extended with > growfs allocate file space. Just as efficiently as a filesystem on a regular disk (ie pretty well, on the whole). Remember that logical volumes exist at the device level, below the filesystem level. The filesystem neither knows nor cares whether it resides on a plain disk or a logical volume; the whole point of logical volumes is to make collections of disks look to all other parts of the system like a single regular disk. Dave Higgen (daveh@xtenk.asd.sgi.com)
daveh@xtenk.asd.sgi.com (David A Higgen) (10/23/90)
In article <1990Oct22.171615.17166@cid.aes.doe.CA>, aspgasd@cidsv01.cid.aes.doe.CA (Alain St-Denis) writes: > Is there a manual that explains all there is to know about logical > volumes? I already read the System Administrator's Guide. Suffering from a touch of multiple-post-itas, aren't we Alain? As I said in my last follow-up, I will try to answer specific questions. > I would like to know how the stripping is implemented and also how the > file space is allocated on a logical volume extended with growfs. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ No, no: this seems to be a widespread confusion. Growfs extends the *filesystem*, not the logical volume. A logical volume is extended by adding more devices to its specification in /etc/lvtab and rerunning mklv; you would do this *before* using growfs. I think there is some confusion because many people have heard the terms "striped files" or "striped filesystems". There are basically two ways you can do volume management & software striping. 1) You can modify the filesystem to have knowledge of the physical devices on which it resides, and add management policies to the filesystem itself to allow it to determine which physical disk a given file block is on, OR 2) You can build an intermediate layer, below the filesystem but above the actual disk drivers, which makes multiple real disk devices look to higher layers like a single device. We have used the latter approach: it is more modular and allows volumes to be constructed from any type of physical disk without modifications to the filesystem code. Our logical volumes are *devices*, the filesystem knows nothing about them. Dave Higgen (daveh@xtenk.asd.sgi.com)
aspgasd@cidsv01.cid.aes.doe.CA (Alain St-Denis) (10/25/90)
In article <72895@sgi.sgi.com>, daveh@xtenk.asd.sgi.com (David A Higgen) writes: > > Suffering from a touch of multiple-post-itas, aren't we Alain? As I said > in my last follow-up, I will try to answer specific questions. Sorry about that. > > No, no: this seems to be a widespread confusion. Growfs extends the > *filesystem*, not the logical volume. A logical volume is extended by > adding more devices to its specification in /etc/lvtab and rerunning > mklv; you would do this *before* using growfs. AH! I get it now... Thank you for the clarification (I'm not gonna say that I knew, you wouldn't believe me :-) ...) > I think there is some confusion because many people have heard the > terms "striped files" or "striped filesystems". > > There are basically two ways you can do volume management & software striping. > > 1) You can modify the filesystem to have knowledge of the physical devices > on which it resides, and add management policies to the filesystem > itself to allow it to determine which physical disk a given file block > is on, > > OR > > 2) You can build an intermediate layer, below the filesystem but above the > actual disk drivers, which makes multiple real disk devices look to > higher layers like a single device. > > We have used the latter approach: it is more modular and allows volumes to > be constructed from any type of physical disk without modifications to the > filesystem code. Our logical volumes are *devices*, the filesystem knows > nothing about them. So, if I understand correctly, the logical volume layer decides where the data blocks end up? If I have a filesystem that I want to "grow", will it start using all the drives immediately or will it fill up the first one and then start to use the next and so on? And if I decide to use striping on a new logical volume, does the driver see the physical disks as one disk and consider that, for example, a track starts on the first and ends on the last disk. That would give faster transfer rates but allows contention on the device, right? Or, are the data blocks allocated based on whatever disk is not busy on the logical device? What I want to know is that by using the logical volumes, I won't strangle my system by making it think that it has only one fast disk instead of n moderatly fast disks. I think these are specific questions. Feel free to criticize my limited knowledge of the topic (and my not so bad but not so good english). Thank you. -- Alain St-Denis Centre informatique de Dorval Environnement Canada astdenis@cid.aes.doe.CA (514) 421-4697