Partition Setup

cto2mac · Posted: Thu Sep 12, 2002 6:33 pm Post subject: Partition Setup

I have two hard drives both are 6Gb I would like to get Gentoo running on my system using the both of them. How would you suggest the breakout of my partitions be? 100M for /boot and such?

Thanks

thegarbageman · Posted: Thu Sep 12, 2002 7:02 pm Post subject: Partition Setup

Personally, I would use about 32M for boot (I would never use all of 100M), 2xRAM for Swap, the rest of hda for "/" and all 6GB of hdb for either /home or /usr (depending on whether I plan on having alot of personal files or alot of programs). Just an opinion.

pjp · Administrator Joined: 16 Apr 2002 Posts: 20067

The opinions on partitioning a system are quite varied. There is no one 'correct' way to do it. Until you have a need to do otherwise, the recommendations in the Installation Instructions will work just fine.

thegarbageman: Out of curiosity, why 32MB for /boot? Why not 30, or 35? Just curious.
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dubiousoul · n00b Joined: 12 Sep 2002 Posts: 17 Location: Tucson, AZ

I actually think this is an excellent candidate for Software RAID.

Set up the first HDD with say 128M /boot, 2*RAM swap, the rest /. Get your system up and running all spiffy-like. Then set up software raid say level 0 (linear) so that in the end / is about 12GB. Or, you could go with any of the other raid levels for better or worse or different performance. Check out the latest Software-RAID HOWTO at http://unthought.net/Software-RAID.HOWTO/.

Why 128M for /boot? Because.. we all love powers of two, right?

--Dylan.

bluesky · Apprentice Joined: 14 Aug 2002 Posts: 230 Location: USA

Hey, dubiousSoul. Very interesting input. I read the article HOWTO but don't know how to maake of it. It doesn't explain if we should use raid software or not. How much will be the performance boost and is there any disadvantages. We need more imput from you, please.

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millenium_psyrax · Posted: Sat Sep 14, 2002 1:03 am Post subject:

I agree with the software RAID. However, don't do the 2 * RAM option. That is essentially a Microsoft formula, and it is illogical. The RAM the more swap space necessary. WRONG. It is actually the inverse. The more RAM the less swap space necassary. I have 320 MB RAM, no way do I need 640Mb Swap file. I have 256Mb for swap, and Linux never touches it.
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pjp · Administrator Joined: 16 Apr 2002 Posts: 20067

bluesky · Apprentice Joined: 14 Aug 2002 Posts: 230 Location: USA

For most home desktops, probably memory dump isn't of any practical use. Some people don't even know what it is.

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dubiousoul · n00b Joined: 12 Sep 2002 Posts: 17 Location: Tucson, AZ

dubiousoul · n00b Joined: 12 Sep 2002 Posts: 17 Location: Tucson, AZ

(A comment on raid-0)

I think that performance is actually a little worse than the HOWTO and I had previously expected. I imagine that given two drives on separate IDE busses, without any other devices, if we think of

drive1 has a rating of N MB/s
drive2 has a rating of P MB/s
busses have a rating of at least max(N,P) MB/s

then one might initially expect a performance of N*P MB/s, but really you're not going to be able to write at the product of the performance of these two drives, you can only write data at the minimum speed supported squared (because it wouln't make sence to write more to one drive than another and say we're done.. by definition raid0 writes exactly half to disk1 and half to disk2). Therefore I'm pretty sure that with the stated setup you should expect ( min(N,P) )^2 MB/s at best. I say at best because you're not always going to get the full writing capability of any drive, there are things like seeks and checksums going on if I remember correctly.

To explore further.. if the drives are on the same IDE bus, you're not going to get max(N,P) MB/s performance, because like before you have to write half to one and half to the other. So in this case you should expect at best min(N,P) MB/s.

Lastly, let's suppose you have ide1 supporting drive1 and ide2 supporting drive2 and cdrom2. Say cdrom has a rating of K MB/s. Now, I have absolutely no concept of how the ide bus decides what speed it can write at if you have one device capable of P MB/s and another of K MB/s, but we can guess a worst-case scenario. Imagine we're reading the cd as fast as we can and writing to the drive as fast as we can.. not terribly uncommon in some cases. The cd is capable of about K MB/s and drive2, taking only half the data, is capable of again ( min(N,P) )^2 MB/s. But we have to account for the CD read.. let's say it gets the same niceness as the HDDs to be fair. Then we can say that our maximum access from IDE bus2 is about avg(P,K) / 2 MB/s, which is indeed slower than P MB/s. Moving backwards, this would make our best case throughput in this setup with everything running ( min( N, avg(P,K) / 2 ) )^2 MB/s. Not very good.

That's a very good explanation of why you really want your hard drives on separate IDE busses, as the sole device on that bus.

--Dylan.

millenium_psyrax · Posted: Thu Sep 19, 2002 2:23 am Post subject:

Naan Yaar · Bodhisattva Joined: 27 Jun 2002 Posts: 1549

Well, this is a quote from Linus. Earlier 2.4 kernels were more swap hungry than recent ones. Also, the RedHat recommendation for swap space is about 2xRAM (for < 2GB). So it is not really obsolete or outre advice.