On 01/08/12 18:21, Bob Friesenhahn wrote:
Something else to be aware of is that even if you don't have a dedicated
ZIL device, zfs will create a ZIL using devices in the main pool so
Terminology nit: The log device is a SLOG. Every ZFS dataset has a
ZIL. Where the ZIL writes (slog or main p
2012-01-08 5:45, Richard Elling wrote:
I think you will see a tradeoff on the read side of the mixed read/write
workload.
Sync writes have higher priority than reads so the order of I/O sent to the disk
will appear to be very random and not significantly coalesced. This is the
pathological worst
> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
> boun...@opensolaris.org] On Behalf Of Bob Friesenhahn
>
> To put things in proper perspective, with 128K filesystem blocks, the
> worst case file fragmentation as a percentage is 0.39%
> (100*1/((128*1024)/512)). On a Microsoft Wi
> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
> boun...@opensolaris.org] On Behalf Of Jim Klimov
>
> 1) Sync writes will land on disk randomly into nearest
> (to disk heads) available blocks, in order to have them
> committed ASAP;
This is true - but you need to make the distin
On Jan 9, 2012, at 5:44 AM, Edward Ned Harvey wrote:
>> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
>> boun...@opensolaris.org] On Behalf Of Bob Friesenhahn
>>
>> To put things in proper perspective, with 128K filesystem blocks, the
>> worst case file fragmentation as a percent
On 01/08/12 20:10, Jim Klimov wrote:
Is it true or false that: ZFS might skip the cache and
go to disks for "streaming" reads?
I don't believe this was ever suggested. Instead, if
data is not already in the file system cache and a
large read is made from disk should the file system
put this d
Thanks for the replies, some more questions follow.
Your answers below seem to contradict each other somewhat.
Is it true that:
1) VDEV cache before b70 used to contain a full copy
of prefetched disk contents,
2) VDEV cache since b70 analyzes the prefetched sectors
and only keeps metadata
On 01/08/12 10:15, John Martin wrote:
I believe Joerg Moellenkamp published a discussion
several years ago on how L1ARC attempt to deal with the pollution
of the cache by large streaming reads, but I don't have
a bookmark handy (nor the knowledge of whether the
behavior is still accurate).
htt
2012-01-09 18:15, John Martin пишет:
On 01/08/12 20:10, Jim Klimov wrote:
Is it true or false that: ZFS might skip the cache and
go to disks for "streaming" reads?
>> (The more I think
>> about it, the more senseless this sentence seems, and
>> I might have just mistaken it with ZIL writes of
On Mon, 9 Jan 2012, Edward Ned Harvey wrote:
I don't think that's correct...
But it is! :-)
Suppose you write a 1G file to disk. It is a database store. Now you start
running your db server. It starts performing transactions all over the
place. It overwrites the middle 4k of the file, an
2012-01-09 19:14, Bob Friesenhahn wrote:
In summary, with zfs's default 128K block size, data fragmentation is
not a significant issue, If the zfs filesystem block size is reduced to
a much smaller value (e.g. 8K) then it can become a significant issue.
As Richard Elling points out, a database l
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On 07/01/12 13:39, Jim Klimov wrote:
> I have transitioned a number of systems roughly by the same
> procedure as you've outlined. Sadly, my notes are not in English so
> they wouldn't be of much help directly;
Yes, my russian is rusty :-).
I have bi
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