From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of David Dyer-Bennet
For example, if you start with an empty drive, and you write a large
amount
of data to it, you will have no fragmentation. (At least, no
significant
fragmentation;
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Marty Scholes
What appears to be missing from this discussion is any shred of
scientific evidence that fragmentation is good or bad and by how much.
We also lack any detail on how much
On Sep 16, 2010, at 12:33 PM, Marty Scholes wrote:
David Dyer-Bennet wote:
Sure, if only a single thread is ever writing to the
disk store at a time.
This situation doesn't exist with any kind of
enterprise disk appliance,
though; there are always multiple users doing stuff.
Ok, I'll
On Wed, September 15, 2010 16:18, Edward Ned Harvey wrote:
For example, if you start with an empty drive, and you write a large
amount
of data to it, you will have no fragmentation. (At least, no significant
fragmentation; you may get a little bit based on random factors.) As life
goes
dd == David Dyer-Bennet d...@dd-b.net writes:
dd Sure, if only a single thread is ever writing to the disk
dd store at a time.
video warehousing is a reasonable use case that will have small
numbers of sequential readers and writers to large files. virtual
tape library is another
David Dyer-Bennet wote:
Sure, if only a single thread is ever writing to the
disk store at a time.
This situation doesn't exist with any kind of
enterprise disk appliance,
though; there are always multiple users doing stuff.
Ok, I'll bite.
Your assertion seems to be that any kind of
On Sep 14, 2010, at 4:58 AM, Edward Ned Harvey wrote:
From: Haudy Kazemi [mailto:kaze0...@umn.edu]
With regard to multiuser systems and how that negates the need to
defragment, I think that is only partially true. As long as the files
are defragmented enough so that each particular read
From: Richard Elling [mailto:rich...@nexenta.com]
Suppose you want to ensure at least 99% efficiency of the drive. At
most 1%
time wasted by seeking.
This is practically impossible on a HDD. If you need this, use SSD.
Lately, Richard, you're saying some of the craziest illogical
On Sep 15, 2010, at 2:18 PM, Edward Ned Harvey wrote:
From: Richard Elling [mailto:rich...@nexenta.com]
Suppose you want to ensure at least 99% efficiency of the drive. At
most 1%
time wasted by seeking.
This is practically impossible on a HDD. If you need this, use SSD.
Lately,
On 09/16/10 09:18 AM, Edward Ned Harvey wrote:
From: Richard Elling [mailto:rich...@nexenta.com]
Suppose you want to ensure at least 99% efficiency of the drive. At
most 1%
time wasted by seeking.
This is practically impossible on a HDD. If you need this, use
On Wed, Sep 15, 2010 at 05:18:08PM -0400, Edward Ned Harvey wrote:
It is absolutely not difficult to avoid fragmentation on a spindle drive, at
the level I described. Just keep plenty of empty space in your drive, and
you won't have a fragmentation problem. (Except as required by COW.) How
From: Richard Elling [mailto:rich...@nexenta.com]
It is practically impossible to keep a drive from seeking. It is also
The first time somebody (Richard) said you can't prevent a drive from
seeking, I just decided to ignore it. But then it was said twice. (Ian.)
I don't get why anybody is
From: Haudy Kazemi [mailto:kaze0...@umn.edu]
With regard to multiuser systems and how that negates the need to
defragment, I think that is only partially true. As long as the files
are defragmented enough so that each particular read request only
requires one seek before it is time to
From: Richard Elling [mailto:rich...@nexenta.com]
With appropriate write caching and grouping or re-ordering of writes
algorithms, it should be possible to minimize the amount of file
interleaving and fragmentation on write that takes place.
To some degree, ZFS already does this. The
Richard Elling wote:
Define fragmentation?
Maybe this is the wrong thread. I have noticed that an old pool can take 4
hours to scrub, with a large portion of the time reading from the pool disks at
the rate of 150+ MB/s but zpool iostat reports 2 MB/s read speed. My naive
interpretation is
The difference between multi-user thinking and single-user thinking is
really quite dramatic in this area. I came up the time-sharing side
(PDP-8, PDP-11, DECSYSTEM-20); TOPS-20 didn't have any sort of disk
defragmenter, and nobody thought one was particularly desirable, because
the normal access
From: Richard Elling [mailto:rich...@nexenta.com]
This operational definition of fragmentation comes from the single-
user,
single-tasking world (PeeCees). In that world, only one thread writes
files
from one application at one time. In those cases, there is a reasonable
expectation that
I was thinking to delete all zfs snapshots before zfs send receive to another
new zpool. Then everything would be defragmented, I thought.
(I assume snapshots works this way: I snapshot once and do some changes, say
delete file A and edit file B. When I delete the snapshot, the file A is
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Orvar Korvar
I was thinking to delete all zfs snapshots before zfs send receive to
another new zpool. Then everything would be defragmented, I thought.
You don't need to delete snaps before
On Sep 13, 2010, at 5:14 AM, Edward Ned Harvey wrote:
From: Richard Elling [mailto:rich...@nexenta.com]
This operational definition of fragmentation comes from the single-
user,
single-tasking world (PeeCees). In that world, only one thread writes
files
from one application at one time.
From: Richard Elling [mailto:rich...@nexenta.com]
Regardless of multithreading, multiprocessing, it's absolutely
possible to
have contiguous files, and/or file fragmentation. That's not a
characteristic which depends on the threading model.
Possible, yes. Probable, no. Consider
On Mon, September 13, 2010 07:14, Edward Ned Harvey wrote:
From: Richard Elling [mailto:rich...@nexenta.com]
This operational definition of fragmentation comes from the single-
user,
single-tasking world (PeeCees). In that world, only one thread writes
files
from one application at one
To summarize,
A) resilver does not defrag.
B) zfs send receive to a new zpool means it will be defragged
Correctly understood?
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On Sep 13, 2010, at 10:54 AM, Orvar Korvar wrote:
To summarize,
A) resilver does not defrag.
B) zfs send receive to a new zpool means it will be defragged
Define fragmentation?
If you follow the wikipedia definition of defragmentation then the
answer is no, zfs send/receive does not
Richard Elling wrote:
On Sep 13, 2010, at 5:14 AM, Edward Ned Harvey wrote:
From: Richard Elling [mailto:rich...@nexenta.com]
This operational definition of fragmentation comes from the single-
user,
single-tasking world (PeeCees). In that world, only one thread writes
files
from one
On Sep 13, 2010, at 9:41 PM, Haudy Kazemi wrote:
Richard Elling wrote:
On Sep 13, 2010, at 5:14 AM, Edward Ned Harvey wrote:
From: Richard Elling [mailto:rich...@nexenta.com
]
This operational definition of fragmentation comes from the single-
user,
single-tasking world (PeeCees). In that
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Orvar Korvar
I am not really worried about fragmentation. I was just wondering if I
attach new drives and zfs send recieve to a new zpool, would count as
defrag. But apparently, not.
On Sep 12, 2010, at 8:27 PM, Edward Ned Harvey wrote:
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Orvar Korvar
I am not really worried about fragmentation. I was just wondering if I
attach new drives and zfs send recieve to a new
I am not really worried about fragmentation. I was just wondering if I attach
new drives and zfs send recieve to a new zpool, would count as defrag. But
apparently, not.
Anyway thank you for your input!
--
This message posted from opensolaris.org
It really depends on your definition of fragmentation. This term is used
differently for various file systems. The UFS notion of fragmentation is
closer to the ZFS notion of gangs.
-- richard
On Sep 11, 2010, at 6:16 AM, Orvar Korvar knatte_fnatte_tja...@yahoo.com
wrote:
I am not really
On 10/09/2010 04:24, Bill Sommerfeld wrote:
C) Does zfs send zfs receive mean it will defrag?
Scores so far:
1 No
2 Yes
maybe. If there is sufficient contiguous freespace in the destination
pool, files may be less fragmented.
But if you do incremental sends of multiple snapshots, you may
A) Resilver = Defrag. True/false?
B) If I buy larger drives and resilver, does defrag happen?
C) Does zfs send zfs receive mean it will defrag?
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On Thu, Sep 9, 2010 at 1:04 PM, Orvar Korvar
knatte_fnatte_tja...@yahoo.com wrote:
A) Resilver = Defrag. True/false?
False. Resilver just rebuilds a drive in a vdev based on the
redundant data stored on the other drives in the vdev. Similar to how
replacing a dead drive works in a hardware
I am speaking from my own observations and nothing scientific such as reading
the code or designing the process.
A) Resilver = Defrag. True/false?
False
B) If I buy larger drives and resilver, does defrag
happen?
No. The first X sectors of the bigger drive are identical to the smaller
On Thu, Sep 9, 2010 at 1:26 PM, Freddie Cash fjwc...@gmail.com wrote:
On Thu, Sep 9, 2010 at 1:04 PM, Orvar Korvar
knatte_fnatte_tja...@yahoo.com wrote:
A) Resilver = Defrag. True/false?
False. Resilver just rebuilds a drive in a vdev based on the
redundant data stored on the other drives
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Orvar Korvar
A) Resilver = Defrag. True/false?
I think everyone will agree false on this question. However, more detail
may be appropriate. See below.
B) If I buy larger drives and
On 09/09/10 20:08, Edward Ned Harvey wrote:
Scores so far:
2 No
1 Yes
No. resilver does not re-layout your data or change whats in the block
pointers on disk. if it was fragmented before, it will be fragmented after.
C) Does zfs send zfs receive mean it will defrag?
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