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enloop
n00b
Joined: 13 Jul 2002
Posts: 16
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 Posted: Mon Jun 02, 2003 11:39 pm Post subject: Will Slower of Two Drives Degrade Primary Drive Performance? |
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I'm taking my first stab at building a new machine, which will run Gentoo. I'll install a new 120g Hitachi/IBM Deskstar 180GXP but would also like to recyle a drive from an old machine, an 80g Maxtor DiamondMax. Both drives are UltraDMA 100, but the Deskstar is rated at 7200 rpm while the Maxtor spins at 5400 rpm.
I've been told that, in such configurations, the speed of the nominally faster drive degrades to that of the older and slower drive. Is that true? Would my nice, new Deskstar take a hit from the slower Maxtor? (FYI: the motherboard will be an Asus A7V8X-X wearing an Athlon 2700 XP+.)
Second question: What's behind the perennial recommendation to put the swap partition on the second (or whatever) drive? Is the impact of putting swap on the slower drive worth worrying about?
Third question: Any recommended partitioning schemes? This will be a desktop machine, but will also be one-half of a little private network behind a hardware router. (The other machine is a Mac w/OS X.) I'll run Apache on the new machine to serve to the Mac, but neither machine will be especially stressed.
Thanks. |
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ctford0
l33t
Joined: 25 Oct 2002
Posts: 774
Location: Lexington, KY,USA
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| Posted: Tue Jun 03, 2003 7:08 am Post subject: |
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In this configuration I dont think you would need to worry about speed degradation with the 7200 rpm drive simply because they are both ata100. If one of the drives was ata100 and the other ata33 then you would definately have a problem, but in this situation i dont think you have anything to worry about. I think this type of logic, 2 drives only run as fast as the slowest, is based on the motherboards capability when detecting ata drives. Since hard drives are only designed to do a certain ata or lower, you can see that the ata33 drive will definitely not run at ata100 with the other, so the motherbord default ide #x to using ata33 so the slower drive will function correctly.
In your case since both drives are ata100 you should have no slow down.
Chris |
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alan.hughes
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Joined: 23 Mar 2003
Posts: 40
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| Posted: Tue Jun 03, 2003 8:13 am Post subject: |
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Just to expand on the reply from ctford0, the critical factor is the IDE bus speed of the drive, not its spin rate, although the performance of your slower drive won't be as good of course.
If you do have a IDE device running at a slower bus speed, you should always put it as the slave drive. For IDE the master drive determines the maximum bus speed, hence if you had a ATA100 slave device and a ATA33 master device, then both devices would be limited to ATA33. Swap them around (ATA100 master, ATA33 slave) and they would both run at their maximum rates.
The above is why you should always put a CD-ROM/DVD-ROM/CD-RW as a slave device if it is sharing an IDE cable with a disk crive. CD-ROM/DVD-ROM/CD-RW devices typically use ATA33. |
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slais-sysweb
Apprentice
Joined: 14 Jun 2002
Posts: 221
Location: London
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| Posted: Tue Jun 03, 2003 10:01 am Post subject: Re: Will Slower of Two Drives Degrade Primary Drive Performa |
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Best to have each hard drive as the master on a separate IDE channel, use the secondary for the CD-ROM etc
| enloop wrote: |
Second question: What's behind the perennial recommendation to put the swap partition on the second (or whatever) drive? Is the impact of putting swap on the slower drive worth worrying about? |
In principle, if the swap is on a separate spindle, using swap will not affect the seek times on the other drive. But (a) this assumes that there are no other partitions on the same drive as swap which contend for access, (b) supposes that the swap is much used. If you have enough ram then you will not see much swap activity (Linux will use it, but rarely), so first advice is: ram is cheap put in as much as your board will take. If you really want to tweak performance then you need to consider the whole of the partitioning scheme; which in turn requires some consideration of what work is being done, which partitions will be most active etc. The general principle is that moving the heads from track to track is slow relative to access time on the same cylinder to keeping the trive from seeking across the disk from partition to partition is a good thing. However, given the 'virtual machine' nature of modern hard drives and disk drivers, it will be difficult to manage this in practice unless ech drive is dedicated to a particular task and probably a single partition.
Remember also that the spindle speed is not the only factor, that affect the maximum rate at which data can be read/written from track to buffer, this is probably faster than ATA100 can handle (look for 'internal transfer rate in the spec') Seek times are much slower and more significant.
| enloop wrote: |
Third question: Any recommended partitioning schemes? This will be a desktop machine, but will also be one-half of a little private network behind a hardware router. (The other machine is a Mac w/OS X.) I'll run Apache on the new machine to serve to the Mac, but neither machine will be especially stressed.
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If you're just experimenting I would start off with the standard swap, /boot and / one disk and /home and possibly /tmp (or /var/tmp) on the other. once its installed running
| Code: | du -scmh /
du -scmh /usr
du -scmh /var |
etc
will enable you to assess disk usage and decide on a more ideal scheme for the next install. You will probably end up doing more than one install even if Gentoo just works  first time!
I[/code]
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djc
sysweb SLAIS UCL |
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