Solaris Slice 2?
A DBA asked whether it's actually risky to use Solaris slice/partition 2 as an ordinary raw-device slice for Informix dbspaces, since documentation says to leave it as the whole-disk slice. Lester Knutsen and Art Kagel said there's no real problem on disks dedicated to Informix: slice 2 is only conventionally reserved for whole-disk imaging. The one caveat is that Solaris fdisk puts the partition/disk label in the first block, and the default slice 2 spans it, so you must start partitions after cylinder 0; other volume managers avoid the issue entirely. Resolved.
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Informix 12.10 Solaris `10 For many years, on older versions of Informix and Solaris, I used slice 2 of disk drives as just another slice. This was exclusively in the context of drives that were entirely used only for Informix raw device dbspaces. Several years ago, when we acquired new Sun T4-1 boxes (not my selection), and we moved to current Informix and Solaris versions, I stopped using slice 2. That is, I left it as the entire disk, and didn't use it for anything. (A useless slice.) I stopped using slice 2 only because of the unanimous information expressed in the Solaris documentation and in many online sources, and figured there must be a good reason to forgo that valuable resource. So, I did. But, I really could use those unused slices. What really is the danger in using slice 2 on drives used exclusively as Informix raw devices? In about 10 years of such use, I never had a problem, but, hey, maybe I was just ignorant and lucky. I'm still ignorant, though. So, I ask again whether anyone really knows the actual danger in using slice 2. Thank you. DG
David, On Solaris, in the old days, for disk that I was using with Informix, to I would re-partition the disks using the format command into a set of partitions that I wanted and would use all available partitions. I think slice 2 by default was suppose to be the whole disk which may be why folks are saying not to use it. So for an 8GB disk I would create 4 x 2GB partitions or for a 36GB disk 6 x6GB partitions. The key is to leave a off-set on the first partition for the disk label that Solaris will put on the disk. I never had a problem re-using partition 2. I would also leave the OS disks and /root as is.... So if a disk is dedicated to Informix then I don't see a problem using partition2 . Now this was before Logical Volumes and other software to manage disks. Regards - Lester On 1/10/17 8:02 PM, DAVID GROVE wrote: > Informix 12.10 > Solaris `10 > > For many years, on older versions of Informix and Solaris, I used slice 2 of > disk drives as just another slice. This was exclusively in the context of > drives that were entirely used only for Informix raw device dbspaces. > > Several years ago, when we acquired new Sun T4-1 boxes (not my selection), and > we moved to current Informix and Solaris versions, I stopped using slice 2. > That is, I left it as the entire disk, and didn't use it for anything. (A > useless slice.) I stopped using slice 2 only because of the unanimous > information expressed in the Solaris documentation and in many online sources, > and figured there must be a good reason to forgo that valuable resource. So, I > did. > > But, I really could use those unused slices. > > What really is the danger in using slice 2 on drives used exclusively as > Informix raw devices? > > In about 10 years of such use, I never had a problem, but, hey, maybe I was > just ignorant and lucky. I'm still ignorant, though. > > So, I ask again whether anyone really knows the actual danger in using slice > 2. > > Thank you. > > DG > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > -- ______________________________________________________________________ Lester Knutsen lester@advancedatatools.com Advanced DataTools Corporation Voice: 703-256-0267 x102 Visit our Web page: http://www.advancedatatools.com ______________________________________________________________________
There is no problem redefining partition 2 to be just another partition. Traditionally this is reserved for performing disk wide low level backup imaging. If you don't intend to do that, you don't need to reserve partition 2. Art On Jan 10, 2017 20:03, "DAVID GROVE" <david.grove@alaska.gov> wrote: Informix 12.10 Solaris `10 For many years, on older versions of Informix and Solaris, I used slice 2 of disk drives as just another slice. This was exclusively in the context of drives that were entirely used only for Informix raw device dbspaces. Several years ago, when we acquired new Sun T4-1 boxes (not my selection), and we moved to current Informix and Solaris versions, I stopped using slice 2. That is, I left it as the entire disk, and didn't use it for anything. (A useless slice.) I stopped using slice 2 only because of the unanimous information expressed in the Solaris documentation and in many online sources, and figured there must be a good reason to forgo that valuable resource. So, I did. But, I really could use those unused slices. What really is the danger in using slice 2 on drives used exclusively as Informix raw devices? In about 10 years of such use, I never had a problem, but, hey, maybe I was just ignorant and lucky. I'm still ignorant, though. So, I ask again whether anyone really knows the actual danger in using slice 2. Thank you. DG ************************************************************ ******************* Forum Note: Use "Reply" to post a response in the discussion forum. --94eb2c12857a4348560545c81117
Thank you both, Lester and Art, for informative replies confirming that it is OK to use slice 2. I had been using that slice for many years, without incident. But stopped when we got new machines a couple years ago. The unanimity of documentation and online voices just scared me (although after about 10 years of no incident, i don't know why-- perhaps because at Informix conference a few years ago I was having a conversation with someone between sessions and mentioned I used slice 2 as just another slice. I was cautioned to not do that, but we both had to go to another session before we could discuss in depth.) Anyway, thank you. DG
It's been some time since I've been involved with Solaris, so this question is purely academic to me... I thought I was told my a Solaris guru at one point that there was a risk of overwriting the partition table if you used slice 2 for general purpose data?
It has nothing to do with partition 2 per se. It has to do with the Solaris partition software program fdisk which places the partition table in the first block of the device and the default partition 2, unlike the other pre-defined partitions, includes that partition table in its defined space. You just have to, as Lester mentioned, skip the first cylinder when defining partition 1 and have the other partitions, including your new partition 2, follow that one on disk, and all will be well. If you use a different volume manager than the default fdisk; such as the Solaris Solstice Volume Manager, Legato, one supplied by your SAN vendor, etc.; then this is not an issue at all since all modern volume managers either place the partition table beyond the last partition (reserving that space and not presenting it to be included in any partition) or before the space offered for the first partition, so you cannot damage the partition table at all. It is only Solaris fdisk partitions that are at risk and again, only if a partition includes the first cylinder. Art Art S. Kagel, President and Principal Consultant ASK Database Management www.askdbmgt.com Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Wed, Jan 11, 2017 at 3:26 PM, PETE MCDONNELL < pete.mcdonnell@ejustsystems.com> wrote: > It's been some time since I've been involved with Solaris, so this > question is > purely academic to me... > > I thought I was told my a Solaris guru at one point that there was a risk > of > overwriting the partition table if you used slice 2 for general purpose > data? > > > ************************************************************ > ******************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --94eb2c05cf72fceadc0545d8229f
Similar to Art and Lester's comments... I never had a problem in the past. I was always just careful never to use cylinder 0. DG