Re: [zfs-discuss] [OpenIndiana-discuss] iops...
I am totally aware of these differences, but it seems some people think RAIDz is nonsense unless you don't need speed at all. My testing shows (so far) that the speed is quite good, far better than single drives. Also, as Eric said, those speeds are for random i/o. I doubt there is very much out there that is truely random i/o except perhaps databases, but then, I would never use raid5/raidz for a DB unless at gunpoint. Well besides databases there are VM datastores, busy email servers, busy ldap servers, busy web servers, and I'm sure the list goes on and on. I'm sure it is much harder to list servers that are truly sequential in IO then random. This is especially true when you have thousands of users hitting it. For busy web servers, I would guess most of the data can be cached, at least over time, and with good amounts of arc/l2arc, this should remove most of that penalty. A spooling server is another thing, for which I don't think raidz would be suitable, although with async i/o will streamline at least some of it. For VM datastores, I totally agree. Vennlige hilsener / Best regards roy -- Roy Sigurd Karlsbakk (+47) 97542685 r...@karlsbakk.net http://blogg.karlsbakk.net/ -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [OpenIndiana-discuss] iops...
On Dec 7, 2010, at 9:49 PM, Edward Ned Harvey opensolarisisdeadlongliveopensola...@nedharvey.com wrote: From: Ross Walker [mailto:rswwal...@gmail.com] Well besides databases there are VM datastores, busy email servers, busy ldap servers, busy web servers, and I'm sure the list goes on and on. I'm sure it is much harder to list servers that are truly sequential in IO then random. This is especially true when you have thousands of users hitting it. Depends on the purpose of your server. For example, I have a ZFS server whose sole purpose is to receive a backup data stream from another machine, and then write it to tape. This is a highly sequential operation, and I use raidz. Some people have video streaming servers. And http/ftp servers with large files. And a fileserver which is the destination for laptop whole-disk backups. And a repository that stores iso files and rpm's used for OS installs on other machines. And data capture from lab equipment. And packet sniffer / compliance email/data logger. and I'm sure the list goes on and on. ;-) Ok, single stream backup servers are one type, but as soon as you have multiple streams, even for large files, then IOPS trumps throughput to a degree, of course if throughput is very bad then that's no good either. Know your workload is key, or have enough $$ to implement RAID10 everywhere. -Ross ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [OpenIndiana-discuss] iops...
From: Edward Ned Harvey [mailto:opensolarisisdeadlongliveopensola...@nedharvey.com] In order to test random reads, you have to configure iozone to use a data set which is much larger than physical ram. Since iozone will write a big file and then immediately afterward, start reading it ... It means that whole file will be in cache unless that whole file is much larger than physical ram. You'll get false read results which are unnaturally high. For this reason, when I'm using an iozone benchmark, I remove as much ram from the system as possible. Sorry. There's a better way. This is straight from the mouth of Don Capps, author of iozone: If you use the -w option, then the test file will be left behind. Then reboot, or umount and mount… If you then use the read test, without the write test and again use -w, then you will achieve what you are describing. Example: iozone -i 0 -w -r $recsize -s $filesize Umount, then remount iozone -i 1 -w -r $recsize -s $filesize ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [OpenIndiana-discuss] iops...
Bear a few things in mind: iops is not iops. snip/ I am totally aware of these differences, but it seems some people think RAIDz is nonsense unless you don't need speed at all. My testing shows (so far) that the speed is quite good, far better than single drives. Also, as Eric said, those speeds are for random i/o. I doubt there is very much out there that is truely random i/o except perhaps databases, but then, I would never use raid5/raidz for a DB unless at gunpoint. Vennlige hilsener / Best regards roy -- Roy Sigurd Karlsbakk (+47) 97542685 r...@karlsbakk.net http://blogg.karlsbakk.net/ -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [OpenIndiana-discuss] iops...
On Dec 7, 2010, at 12:46 PM, Roy Sigurd Karlsbakk r...@karlsbakk.net wrote: Bear a few things in mind: iops is not iops. snip/ I am totally aware of these differences, but it seems some people think RAIDz is nonsense unless you don't need speed at all. My testing shows (so far) that the speed is quite good, far better than single drives. Also, as Eric said, those speeds are for random i/o. I doubt there is very much out there that is truely random i/o except perhaps databases, but then, I would never use raid5/raidz for a DB unless at gunpoint. Well besides databases there are VM datastores, busy email servers, busy ldap servers, busy web servers, and I'm sure the list goes on and on. I'm sure it is much harder to list servers that are truly sequential in IO then random. This is especially true when you have thousands of users hitting it. -Ross ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [OpenIndiana-discuss] iops...
From: Roy Sigurd Karlsbakk [mailto:r...@karlsbakk.net] Bear a few things in mind: iops is not iops. snip/ I am totally aware of these differences, but it seems some people think RAIDz is nonsense unless you don't need speed at all. My testing shows (so far) that the speed is quite good, far better than single drives. There is a grain of truth. For sequential IO, either reads or writes, raidz will be much faster than a single drive. For random IO, it's more complex... If you're doing random writes, then ZFS will make them into sequential IO, and hence, your raidz will greatly outperform a single drive. If you're doing random reads, you will get the performance of a single drive, at best. In order to test random reads, you have to configure iozone to use a data set which is much larger than physical ram. Since iozone will write a big file and then immediately afterward, start reading it ... It means that whole file will be in cache unless that whole file is much larger than physical ram. You'll get false read results which are unnaturally high. For this reason, when I'm using an iozone benchmark, I remove as much ram from the system as possible. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [OpenIndiana-discuss] iops...
From: Ross Walker [mailto:rswwal...@gmail.com] Well besides databases there are VM datastores, busy email servers, busy ldap servers, busy web servers, and I'm sure the list goes on and on. I'm sure it is much harder to list servers that are truly sequential in IO then random. This is especially true when you have thousands of users hitting it. Depends on the purpose of your server. For example, I have a ZFS server whose sole purpose is to receive a backup data stream from another machine, and then write it to tape. This is a highly sequential operation, and I use raidz. Some people have video streaming servers. And http/ftp servers with large files. And a fileserver which is the destination for laptop whole-disk backups. And a repository that stores iso files and rpm's used for OS installs on other machines. And data capture from lab equipment. And packet sniffer / compliance email/data logger. and I'm sure the list goes on and on. ;-) ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
