Re: [zfs-discuss] Mixing SATA PATA Drives
On Fri, Sep 14, 2007 at 01:48:40PM -0500, Christopher Gibbs wrote: I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? ...a late reply here, but i'm slightly surprised none of the other respondents mentioned this. The PATA drive is not any slower in raw throughput than the SATA disks. a typical 250G disk has a max transfer rate of maybe 60MB/sec, so the attachment speed will not make a difference. i/o to/from the disk's cache will be marginally slower but you want to disable the write cache for data integrity anyway. If the SATA disks have NCQ, you'd lose on some random i/o workloads by adding the PATA disk. But, i think that you need SATA300 to support that feature. danno -- Dan Pritts, System Administrator Internet2 office: +1-734-352-4953 | mobile: +1-734-834-7224 ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Mixing SATA PATA Drives
Dan Pritts wrote: On Fri, Sep 14, 2007 at 01:48:40PM -0500, Christopher Gibbs wrote: I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? ...a late reply here, but i'm slightly surprised none of the other respondents mentioned this. The PATA drive is not any slower in raw throughput than the SATA disks. a typical 250G disk has a max transfer rate of maybe 60MB/sec, so the attachment speed will not make a difference. True, but I'd image things go wonky if two PATA drives (master and slave) are used. i/o to/from the disk's cache will be marginally slower but you want to disable the write cache for data integrity anyway. Do you? I though ZFS enabled the drive cache when it used the entire drive. Ian. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Mixing SATA PATA Drives
Great, that's the answer I was looking for. My current emphasis is on storage rather than performance. So I just wanted to make sure that mixing the two speeds would be just as safe as using only one kind. Thanks! On 9/17/07, Eric Schrock [EMAIL PROTECTED] wrote: Yes, the pool would run at the speed of the slowest drive. There is an open RFE to better balance allocations acros variable latency toplevel vdevs, but within a toplevel vdev there's not much we can do; we need to make sure your data is on disk with sufficient replication before returning success. - Eric On Mon, Sep 17, 2007 at 01:22:40PM -0500, Christopher Gibbs wrote: Anyone? On 9/14/07, Christopher Gibbs [EMAIL PROTECTED] wrote: I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? Thanks for your input. - Chris -- Christopher Gibbs Email / LDAP Administrator Web Integration Programming Abilene Christian University ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss -- Eric Schrock, Solaris Kernel Development http://blogs.sun.com/eschrock ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Mixing SATA PATA Drives
I'm far from an expert but my understanding is that the zil is spread across the whole pool by default so in theory the one drive could slow everything down. I don't know what it would mean in this respect to keep the PATA drive as a hot spare though. -Tim Christopher Gibbs wrote: Anyone? On 9/14/07, Christopher Gibbs [EMAIL PROTECTED] wrote: I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? Thanks for your input. - Chris ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Mixing SATA PATA Drives
Yes performance will suffer, but it's a bit difficult to say by how much. Both pool transaction group writes and zil writes are spread across all devices. It depends on what applications you will run as to how much use is made of the zil. Maybe you should experiment and see if performance is good enough. Neil. Tim Spriggs wrote: I'm far from an expert but my understanding is that the zil is spread across the whole pool by default so in theory the one drive could slow everything down. I don't know what it would mean in this respect to keep the PATA drive as a hot spare though. -Tim Christopher Gibbs wrote: Anyone? On 9/14/07, Christopher Gibbs [EMAIL PROTECTED] wrote: I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? Thanks for your input. - Chris ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Mixing SATA PATA Drives
Yes, the pool would run at the speed of the slowest drive. There is an open RFE to better balance allocations acros variable latency toplevel vdevs, but within a toplevel vdev there's not much we can do; we need to make sure your data is on disk with sufficient replication before returning success. - Eric On Mon, Sep 17, 2007 at 01:22:40PM -0500, Christopher Gibbs wrote: Anyone? On 9/14/07, Christopher Gibbs [EMAIL PROTECTED] wrote: I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? Thanks for your input. - Chris -- Christopher Gibbs Email / LDAP Administrator Web Integration Programming Abilene Christian University ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss -- Eric Schrock, Solaris Kernel Development http://blogs.sun.com/eschrock ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Mixing SATA PATA Drives
If your priorities were different, or for others pondering a similar question, the PATA disk might be a hotspare. This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
[zfs-discuss] Mixing SATA PATA Drives
I suspect it's probably not a good idea but I was wondering if someone could clarify the details. I have 4 250G SATA(150) disks and 1 250G PATA(133) disk. Would it cause problems if I created a raidz1 pool across all 5 drives? I know the PATA drive is slower so would it slow the access across the whole pool or just when accessing that disk? Thanks for your input. - Chris ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
