Re: [zfs-discuss] write cache and cache flush

Hello Miles, Monday, February 2, 2009, 7:20:49 PM, you wrote: >> "gm" == Greg Mason writes: >> "g" == Gary Mills writes: MN> gm> I know disabling the ZIL is an Extremely Bad Idea, MN> but maybe you don't care about trashed thunderbird databases. You MN> just don't want to lose th

Re: [zfs-discuss] write cache and cache flush

> "gm" == Greg Mason writes: > "g" == Gary Mills writes: gm> I know disabling the ZIL is an Extremely Bad Idea, but maybe you don't care about trashed thunderbird databases. You just don't want to lose the whole pool to ``status: The pool metadata is corrupted and cannot be opened.

Re: [zfs-discuss] write cache and cache flush

Sounds like the device it not ignoring the cache flush requests sent down by ZFS/zil commit. If the SSD is able the drain it's internal buffer to flash on a power outage; then it needs to ignore the cache flush. You can do this on a per device basis, It's kludgy tuning but hope the instructi

Re: [zfs-discuss] write cache and cache flush

Jim Mauro wrote: > You have SSD's for the ZIL (logzilla) enabled, and ZIL IO > is what is hurting your performance...Hmmm > > I'll ask the stupid question (just to get it out of the way) - is > it possible that the logzilla is undersized? > > Did you gather data using Richard Elling's zilstat (

Re: [zfs-discuss] write cache and cache flush

On Fri, 30 Jan 2009, Greg Mason wrote: > A Linux NFS file server, with a few terabytes of fibre-attached disk, > using XFS. > > I'm trying to get these Thors to perform at least as well as the current > setup. A performance hit is very hard to explain to our users. I have heard that Linux NFS ser

Re: [zfs-discuss] write cache and cache flush

I'll give this a script a shot a little bit later today. For ZIL sizing, I'm using either 1 or 2 32G Intel X25-E SSDs in my tests, which, according to what I've read, is 2-4 times larger than the maximum that ZFS can possibly use. We've got 32G of system memory in these Thors, and (if I'm not m

Re: [zfs-discuss] write cache and cache flush

You have SSD's for the ZIL (logzilla) enabled, and ZIL IO is what is hurting your performance...Hmmm I'll ask the stupid question (just to get it out of the way) - is it possible that the logzilla is undersized? Did you gather data using Richard Elling's zilstat (included below)? Thanks, /ji

Re: [zfs-discuss] write cache and cache flush

> If there was a latency issue, we would see such a problem with our > existing file server as well, which we do not. We'd also have much > greater problems than just file server performance. > > So, like I've said, we've ruled out the network as an issue. I should also add that I've tested the

Re: [zfs-discuss] write cache and cache flush

Jim Mauro wrote: > >> This problem only manifests itself when dealing with many small files >> over NFS. There is no throughput problem with the network. > But there could be a _latency_ issue with the network. If there was a latency issue, we would see such a problem with our existing file ser

Re: [zfs-discuss] write cache and cache flush

> This problem only manifests itself when dealing with many small files > over NFS. There is no throughput problem with the network. But there could be a _latency_ issue with the network. [snip] > I've done my homework on this issue, I've ruled out the network as an > issue, as well as the NFS

Re: [zfs-discuss] write cache and cache flush

7200 RPM SATA disks. Tim wrote: > > > On Fri, Jan 30, 2009 at 8:24 AM, Greg Mason > wrote: > > A Linux NFS file server, with a few terabytes of fibre-attached disk, > using XFS. > > I'm trying to get these Thors to perform at least as well as the current >

Re: [zfs-discuss] write cache and cache flush

I should also add that this "creating many small files" issue is the ONLY case where the Thors are performing poorly, which is why I'm focusing on it. Greg Mason wrote: > A Linux NFS file server, with a few terabytes of fibre-attached disk, > using XFS. > > I'm trying to get these Thors to per

Re: [zfs-discuss] write cache and cache flush

On Fri, Jan 30, 2009 at 8:24 AM, Greg Mason wrote: > A Linux NFS file server, with a few terabytes of fibre-attached disk, > using XFS. > > I'm trying to get these Thors to perform at least as well as the current > setup. A performance hit is very hard to explain to our users. > What type of spi

Re: [zfs-discuss] write cache and cache flush

A Linux NFS file server, with a few terabytes of fibre-attached disk, using XFS. I'm trying to get these Thors to perform at least as well as the current setup. A performance hit is very hard to explain to our users. > Perhaps I missed something, but what was your previous setup? > I.e. what di

Re: [zfs-discuss] write cache and cache flush

On 01/29/09 21:32, Greg Mason wrote: > This problem only manifests itself when dealing with many small files > over NFS. There is no throughput problem with the network. > > I've run tests with the write cache disabled on all disks, and the cache > flush disabled. I'm using two Intel SSDs for

Re: [zfs-discuss] write cache and cache flush

This problem only manifests itself when dealing with many small files over NFS. There is no throughput problem with the network. I've run tests with the write cache disabled on all disks, and the cache flush disabled. I'm using two Intel SSDs for ZIL devices. This setup is faster than using the

Re: [zfs-discuss] write cache and cache flush

the funny thing is that I'm showing a performance improvement over write caches + cache flushes. The only way these pools are being accessed is over NFS. Well, at least the only way I care about when it comes to high performance. I'm pretty sure it would give a performance hit locally, but I do

Re: [zfs-discuss] write cache and cache flush

Multiple Thors (more than 2?), with performance problems. Maybe it's the common demnominator - the network. Can you run local ZFS IO loads and determine if performance is expected when NFS and the network are out of the picture? Thanks, /jim Greg Mason wrote: > So, I'm still beating my head aga

Re: [zfs-discuss] write cache and cache flush

If all write caches are truly disabled, then disabling the cache flush won't affect the safety of your data. It will change your performance characteristics, almost certainly for the worse. -- This message posted from opensolaris.org ___ zfs-discuss ma

[zfs-discuss] write cache and cache flush

So, I'm still beating my head against the wall, trying to find our performance bottleneck with NFS on our Thors. We've got a couple Intel SSDs for the ZIL, using 2 SSDs as ZIL devices. Cache flushing is still enabled, as are the write caches on all 48 disk devices. What I'm thinking of doing i