Re: Re[2]: [zfs-discuss] Setting up for zfsboot
Le 5 avr. 07 à 08:28, Robert Milkowski a écrit : Hello Matthew, Thursday, April 5, 2007, 1:08:25 AM, you wrote: MA> Lori Alt wrote: Can write-cache not be turned on manually as the user is sure that it is only ZFS that is using the entire disk? yes it can be turned on. But I don't know if ZFS would then know about it. I'd still feel more comfortably with it being turned off unless ZFS itself does it. But maybe someone from the ZFS team can clarify this. I think that it's true that ZFS would not know about the write cache and thus you wouldn't get the benefit of it. MA> Actually, all that matters is that the write cache is on -- doesn't MA> matter whether ZFS turned it on or you did it manually. (However, make MA> sure that the write cache doesn't turn itself back off when you reboot / MA> lose power...) SCSI write cache flush commands will be issued regardless if zfs has a whole disk or only a slice then, right? That's correct. The code path that issue flushes to the write cache, do not check whether or no the caches are enabled. -- Best regards, Robertmailto:[EMAIL PROTECTED] http://milek.blogspot.com ___ 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[2]: [zfs-discuss] Setting up for zfsboot
Hello Adam, Wednesday, April 4, 2007, 11:41:58 PM, you wrote: AL> On Wed, Apr 04, 2007 at 11:04:06PM +0200, Robert Milkowski wrote: >> If I stop all activity to x4500 with a pool made of several raidz2 and >> then I issue spare attach I get really poor performance (1-2MB/s) on a >> pool with lot of relatively small files. AL> Does that mean the spare is resilvering when you collect the performance AL> data? I think a fair test would be to compare the performance of a fully AL> functional RAID-Z stripe against a one with a missing (absent) device. Sorry, I wasn't clear. I'm not talking about performance while spare is resilvering. I'm talking about resilver performance itself while all other IOs are absent. Resilver itself is slow (lot of files) with raidz2 here. -- Best regards, Robertmailto:[EMAIL PROTECTED] http://milek.blogspot.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re[2]: [zfs-discuss] Setting up for zfsboot
Hello Matthew, Thursday, April 5, 2007, 1:08:25 AM, you wrote: MA> Lori Alt wrote: >> >>> Can write-cache not be turned on manually as the user is sure that it is >>> only ZFS that is using the entire disk? >>> >>> >>> yes it can be turned on. But I don't know if ZFS would then know about it. >>> >>> I'd still feel more comfortably with it being turned off unless ZFS itself >>> does it. >>> >>> But maybe someone from the ZFS team can clarify this. >> I think that it's true that ZFS would not know about the >> write cache and thus you wouldn't get the benefit of it. MA> Actually, all that matters is that the write cache is on -- doesn't MA> matter whether ZFS turned it on or you did it manually. (However, make MA> sure that the write cache doesn't turn itself back off when you reboot / MA> lose power...) SCSI write cache flush commands will be issued regardless if zfs has a whole disk or only a slice then, right? -- Best regards, Robertmailto:[EMAIL PROTECTED] http://milek.blogspot.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re[2]: [zfs-discuss] Setting up for zfsboot
Hello Adam, Wednesday, April 4, 2007, 7:08:07 PM, you wrote: AL> On Wed, Apr 04, 2007 at 03:34:13PM +0200, Constantin Gonzalez wrote: >> - RAID-Z is _very_ slow when one disk is broken. AL> Do you have data on this? The reconstruction should be relatively cheap AL> especially when compared with the initial disk access. If I stop all activity to x4500 with a pool made of several raidz2 and then I issue spare attach I get really poor performance (1-2MB/s) on a pool with lot of relatively small files. -- Best regards, Robertmailto:[EMAIL PROTECTED] http://milek.blogspot.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re[2]: [zfs-discuss] Setting up for zfsboot
Hello Constantin, Wednesday, April 4, 2007, 3:34:13 PM, you wrote: CG> - RAID-Z is slow when writing, you basically get only one disk's bandwidth. CG> (Yes, with variable block sizes this might be slightly better...) No, it's not. It's actually very fast for writing, in many cases it would be faster than raid-10 (both made of 4 disks). Now doing random reads is slow... -- Best regards, Robertmailto:[EMAIL PROTECTED] http://milek.blogspot.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
