[ale] EVMS + software RAID??

[Trey Darley]

Well, thanks!
I was mainly concerned with the question of whether there is any  
greater virtue associated with doing evms (or lvm) before mirroring or  
vice-versa.
Thanks for the feedback on EVMS.
As for the question of 2.5 direction, I guess I ought to get my act  
together and find a rss feed for the changelogs. :-)
Re: the virtue of mirroring swap. I have followed some discussions on  
this topic. The idea was put forward that if a disk failed (with  
striped swap) Mr. Kernel might get pretty annoyed. On the other hand,  
by mirroring swap you ought to be protected from a kernel fault in the  
case of a disk failure. (Admittedly a inexcusably ram-starved box to be  
swapping so.)

--Trey

On Thursday, December 5, 2002, at 04:45 PM, Jeffrey B. Layton wrote:

> trey wrote:
>
>> Has anyone had any experience with this combo? I know that I did a
>> similar thing a year or two ago with a Solaris 8 system using their
>> Disksuite. It was like, create stripes, then create metadevices, then
>> create cats?? Something like that. I guess the long and short of it is
>> that I want to mirror two 120gig drives. Partition table is like:
>> root - 5000 meg
>> swap - 2000 meg
>>
>> The remaining 113gig or so I want to be able to create metadevices and
>> have some flexibility in resizing them dynamically as needed, without
>> making my mirror desync.
>> I guess the question is multi-part.
>>
>> 1 - Does anyone have any experience with EVMS? Any caveats?
>> 2 - Do I want to create one big 113 gig filesystem, convert it to a
>> metadevice, then mirror that metadevice, then subdivide that
>> metadevice into "partitions" ? Or have I mucked up the order of
>> operations here?
>>
>
>   Let's see... I'm not sure I follow what you want to do. You've got  
> two
> 120 gig drives with 5 Gigs for root and 2 gigs for swap on each.
> Is this correct so far? Do you want to mirror root? (It doesn't make
> much sense to mirror swap, but you can strip swap across the
> two drives). So, do you want to mirror the first partition (/dev/hda1)
> on each which contains root (RAID-1)? Then /dev/hda2 is used for
> swap on each drive (I'll have to look at around at how you setup
> striping for swap).
>  Then with the remaining about 113 Gigs you want to mirror them,
> but have the ability to grow? If so, you can use software RAID-1
> to mirror the partitions (for the sake of argument /dev/hda3) and
> then build a logical volume on top of this mirror. Or you do the
> opposite, build a LV on each drive, then use software RAID-1
> to mirror them. I don't know which one would be better or why.
>   Of course, you can carve up the 113 Gigs as you want and mix
> and match software RAID and LVM.
>   On the topic of EVMS, I have used it in the past. I really liked it.
> However, if you have followed the 2.5 kernel development, EVMS
> is toast except for the user portion of the code. EVMS will be built
> on top of the Device Manager (DM) and it appears that LVM2 will
> be put into the 2.5 kernel RSN. I use LVM at work and it's just fine
> (it's very similiar to the HP LVM). I had only one problem when a
> disk in the LVM died (one of the PV's). EVMS allowed me to
> mount the LV as read-only and pull whatever data I could off of the
> LV.
>   If you need to read more about LVM go to www.sistina.com and
> look for LVM. To learn more about software RAID, I recommend
> the following articles:
>
> http://www-106.ibm.com/developerworks/linux/library/l-raid1/index.html
> http://www-106.ibm.com/developerworks/linux/library/l-raid2/ 
> ?dwzone=linux
>
> Good Luck!
>
> Jeff
>
>
>
>
>
>>
>> -- Trey
>> +++--------------------------------------------------------------+++
>>
>> Trey Darley - Chief Technical Monkey
>> AIS Computers - www.aiscomputers.com
>> 165 Carnegie Place
>> Fayetteville, GA 30214
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>> Mobile: 404.455.1516
>>
>> [Please note that the opinions I express are not to be in any way
>> construed as those of AIS, unless that is expressly stated.]
>>
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