----- Forwarded message from Gordan Bobic <gor...@bobich.net> ----- From: Gordan Bobic <gor...@bobich.net> Date: Sat, 06 Aug 2011 21:37:30 +0100 To: vser...@list.linux-vserver.org Subject: Re: [vserver] hybrid zfs pools as iSCSI targets for vserver Reply-To: vser...@list.linux-vserver.org User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.18) Gecko/20110621 Red Hat/3.1.11-2.el6_1 Lightning/1.0b2 Thunderbird/3.1.11
On 08/06/2011 09:30 PM, John A. Sullivan III wrote: > On Sat, 2011-08-06 at 21:40 +0200, Eugen Leitl wrote: >> I've recently figured out how to make low-end hardware (e.g. HP N36L) >> work well as zfs hybrid pools. The system (Nexenta Core + napp-it) >> exports the zfs pools as CIFS, NFS or iSCSI (Comstar). >> >> 1) is this a good idea? >> >> 2) any of you are running vserver guests on iSCSI targets? Happy with it? >> > Yes, we have been using iSCSI to hold vserver guests for a couple of > years now and are generally unhappy with it. Besides our general > distress at Nexenta, there is the constraint of the Linux file system. > > Someone please correct me if I'm wrong because this is a big problem for > us. As far as I know, Linux file system block size cannot exceed the > maximum memory page size and is limited to no more than 4KB. I'm pretty sure it is _only_ limited by memory page size, since I'm pretty sure I remember that 8KB blocks were available on SPARC. > iSCSI > appears to acknowledge every individual block that is sent. That means > the most data one can stream without an ACK is 4KB. That means the > throughput is limited by the latency of the network rather than the > bandwidth. Hmm, buffering in the FS shouldn't be dependant on the block layer immediately acknowledging unless you are issuing fsync()/barriers. What FS are you using on top of the iSCSI block device and is your application fsync() heavy? Gordan ----- End forwarded message ----- -- Eugen* Leitl <a href="http://leitl.org";>leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
