Re: SV: [gentoo-performance] Optimal fstab on raid

[Brian Kroth]

I've found XFS to be a little disappointing for day to day sort of 
stuff.  I use ReiserFS almost exclusively, though I have seen how XFS 
out performs it in large file related things.  In general, most system 
files are small (a couple of MB max) as are a lot of user files.  You 
can do a comparison on your own system with a simple find command. 
Perhaps a media volume with XFS would make sense, but then again you're 
probably reading it mostly and not writing too much.

I use ext2 for any filesystem where you can avoid the overhead of 
journaling if it's not required, like /tmp.  One downside I've noticed 
with ReiserFS is the long mount time for large (~500G) volumes.

I don't have any numbers for any of this right now, and am often 
skeptical of those you see in various articles or even Hans's own site. 
  I've been planning on doing my own survey including Reiser4 once it 
comes out and how they may relate to RAID configurations as well.  So 
far, this is really just based on some simple bonnie tests and 
experience with my servers and workstations at work and home over the 
past couple of years.

Also, if the tree grows much more, or whether or not you want a 
distfiles cache, you may want to increase the size of those portage 
partitions.

Brian

Mikko Husari wrote:
> BRIAN PAUL KROTH wrote:
>>> well, my experiences with distcc has not been quite nice, some of the
>>>
>>> packages does not behave well with distributed compiling... or what
>>> did
>>> you mean with buildsystem? and searching from portage over nfs is much
>>>
>>> slower than searching local portage tree...
>>>
>> As someone else said esearch, eix are very nice tools that work best for searching even when you have a local portage tree.
>>
>> What I actually meant by build system is to only build packages on one machine and let your other hosts use those binary packages rather than trying to build and compile everywhere.  If you want you can use distcc on top of that but it's not necessary.  This was more so in relation to your home networking proposal.  It results in a single build environment so all of your machines that use those packages behave the same and there's only one machine doing portage tree syncing which means less disk trashing and (external) network traffic.  In my experience it ends up performing much better and being easier to manage.  Then you can dedicate your other machines to their actual purposes rather than trying to fix build problems in many different places.
>>
>> As to your original question, again, it depends on what you're doing.  RAID0 is best for fast writes in which you don't care about reliability - basically scratch space.  Something like portage might be suited for this.  Then again, the portage tree is really meant as a local cache of the master tree.  As such its supposed to be read from more often than written to.  RAID1 provides reliability and read performance since you can read from one of several disks to achieve the same results.  Write performance for RAID1 is obviously not as good, but how often are you really writing to /opt or /usr for instance.  If you're going software raid, both of these come almost free in terms of overhead involved.  With higher levels you'll definitely want true hardware level raid, not some cheap BIOS implemented version.  I'd previously read, and can't find the document just now, that RAID10 offers the combination of both of these and the best performance (better than RAID5 as well).  Th
ou
>> gh that may be out of the question in terms of the number of disks involved.
>>
>> Here's what I've done in the past for client machines...
>>
>> Partition1 RAID1 15G /
>> Partition2 1xRAM/disk swap (it should automatically be striped)
>> Partition3 RAID0 5G /tmp (you may want more if you're doing video editing or something like that)
>> Partition4 (extended)
>> Partition5 RAID1 5G /var (you may want more if you're building packages or something)
>> Partition6 RAID1 * /home (the rest of it)
>>
>> Also, if you want to be able to tweak your partition sizes, LVM offers striping and mirroring so you don't need to layer software raid on top of or underneath that as well.
>>
>> Hope that helps,
>> Brian
>>
> well, all of this has been really helpfull. my current plans for my
> desktop-pc:
>
> MOUNT            PSIZE    MSIZE    FSTYPE    BLOCKS    RAIDLEVEL
> /                             5G     5G    xfs    4096    1
> /home                      *      *    xfs    4096    1
> /var                        5G     5G    xfs    4096    1
> /usr                        6G     6G    xfs    4096    1
> /usr/portage                     500     1G    reiser    2048    0
> /usr/portage/distfiles      500     1G    xfs    4096    0
> /tmp                                 2G     4G    reiser    4096    0
>
>
> im just not so sure about the filesystem choices...
>
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