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
Anyone? On 9/14/07, Christopher Gibbs <chris.gibbs at acu.edu> 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
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 <chris.gibbs at acu.edu> 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 >> >> > > >
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 <chris.gibbs at acu.edu> 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 at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss-- Eric Schrock, Solaris Kernel Development http://blogs.sun.com/eschrock
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 <eric.schrock at sun.com> 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 <chris.gibbs at acu.edu> 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 at opensolaris.org > > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > > -- > Eric Schrock, Solaris Kernel Development http://blogs.sun.com/eschrock >
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 <chris.gibbs at acu.edu> 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 at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
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
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
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.
On Thu, Nov 08, 2007 at 12:42:01PM +1300, Ian Collins wrote:> True, but I''d image things go wonky if two PATA drives (master and > slave) are used.Absolutely. Never use PATA slave config if you care at all about performance.> > 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.I think you''re right, I think what i was thinking of was that ZFS (and anyone else, really, but ZFS is where i''ve heard about it) wants to be awful sure that the drive actually flushes its write cache when you ask for it. Regardless, the speed difference is marginal. danno -- Dan Pritts, System Administrator Internet2 office: +1-734-352-4953 | mobile: +1-734-834-7224
On Thu, 8 Nov 2007, Ian Collins wrote:> Dan Pritts wrote: >> 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.AFAIK the write cache is always enabled for PATA drives: http://src.opensolaris.org/source/search?q=ata_write_cache+&defs=&refs=&path=&hist=&project=%2Fonnv -Albert