@opensolaris.org
Subject: Re: [zfs-discuss] SSDs adequate ZIL devices?
So why buy SSD for ZIL at all?
For the record, not all SSDs ignore cache flushes. There are at
least
two SSDs sold today that guarantee synchronous write semantics; the
Sun/Oracle LogZilla and the DDRdrive X1. Also, I believe
Christopher George wrote:
So why buy SSD for ZIL at all?
For the record, not all SSDs ignore cache flushes. There are at least
two SSDs sold today that guarantee synchronous write semantics; the
Sun/Oracle LogZilla and the DDRdrive X1. Also, I believe it is more
LogZilla? Are these
Arve Paalsrud wrote:
Not to forget the The Deneva Reliability disks from OCZ that just got
released. See
http://www.oczenterprise.com/details/ocz-deneva-reliability-2-5-emlc-ssd.html
The Deneva Reliability family features built-in supercapacitor (SF-1500
models) that acts as a temporary
On Wed, June 16, 2010 03:03, Arne Jansen wrote:
Christopher George wrote:
For the record, not all SSDs ignore cache flushes. There are at least
two SSDs sold today that guarantee synchronous write semantics; the
Sun/Oracle LogZilla and the DDRdrive X1. Also, I believe it is more
LogZilla?
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I've very in-frequently seen the RAMSAN devices mentioned here. Probably
due to price.
However a long time ago I think I remember someone suggesting a build it
yourself RAMSAN.
Where is the down side of one or 2 OS boxes with a whole lot of RAM
On Wed, June 16, 2010 10:44, Arne Jansen wrote:
David Magda wrote:
I'm not sure you'd get the same latency and IOps with disk that you can
with a good SSD:
http://blogs.sun.com/brendan/entry/slog_screenshots
[...]
Please keep in mind I'm talking about a usage as ZIL, not as L2ARC or
On Wed, June 16, 2010 11:02, David Magda wrote:
[...]
Yes, I understood it as suck, and that link is for ZIL. For L2ARC SSD
numbers see:
s/suck/such/
:)
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David Magda wrote:
On Wed, June 16, 2010 11:02, David Magda wrote:
[...]
Yes, I understood it as suck, and that link is for ZIL. For L2ARC SSD
numbers see:
s/suck/such/
ah, I tried to make sense from 'suck' in the sense of 'just writing
sequentially' or something like that ;)
:)
David Magda wrote:
On Wed, June 16, 2010 10:44, Arne Jansen wrote:
David Magda wrote:
I'm not sure you'd get the same latency and IOps with disk that you can
with a good SSD:
http://blogs.sun.com/brendan/entry/slog_screenshots
[...]
Please keep in mind I'm talking about a usage as
On Wed, 16 Jun 2010, Arne Jansen wrote:
Please keep in mind I'm talking about a usage as ZIL, not as L2ARC or main
pool. Because ZIL issues nearly sequential writes, due to the NVRAM-protection
of the RAID-controller the disk can leave the write cache enabled. This means
the disk can write
Arne Jansen wrote:
David Magda wrote:
On Wed, June 16, 2010 10:44, Arne Jansen wrote:
David Magda wrote:
I'm not sure you'd get the same latency and IOps with disk that you can
with a good SSD:
http://blogs.sun.com/brendan/entry/slog_screenshots
[...]
Please keep in mind I'm talking
Bob Friesenhahn wrote:
On Wed, 16 Jun 2010, Arne Jansen wrote:
Please keep in mind I'm talking about a usage as ZIL, not as L2ARC or
main
pool. Because ZIL issues nearly sequential writes, due to the
NVRAM-protection
of the RAID-controller the disk can leave the write cache enabled.
This
On Wed, June 16, 2010 15:15, Arne Jansen wrote:
I double checked before posting: I can nearly saturate a 15k disk if I
make full use of the 32 queue slots giving 137 MB/s or 34k IOPS/s. Times
3 nearly matches the above mentioned 114k IOPS :)
34K*3 = 102K. 12K isn't anything to sneeze at :)
David Magda wrote:
On Wed, June 16, 2010 15:15, Arne Jansen wrote:
I double checked before posting: I can nearly saturate a 15k disk if I
make full use of the 32 queue slots giving 137 MB/s or 34k IOPS/s. Times
3 nearly matches the above mentioned 114k IOPS :)
34K*3 = 102K. 12K isn't
On Wed, Jun 16, 2010 at 04:44:07PM +0200, Arne Jansen wrote:
Please keep in mind I'm talking about a usage as ZIL, not as L2ARC or main
pool. Because ZIL issues nearly sequential writes, due to the NVRAM-protection
of the RAID-controller the disk can leave the write cache enabled. This means
There has been many threads in the past asking about ZIL
devices. Most of them end up in recommending Intel X-25
as an adequate device. Nevertheless there is always the
warning about them not heeding cache flushes. But what use
is a ZIL that ignores cache flushes? If I'm willing to
tolerate that
On Tue, 15 Jun 2010, Arne Jansen wrote:
In case of a power failure I will likely lose about as many writes
as I do with SSDs, a few milliseconds.
I agree with your concerns, but the data loss may span as much as 30
seconds rather than just a few milliseconds.
Using an SSD as the ZIL allows
So why buy SSD for ZIL at all?
For the record, not all SSDs ignore cache flushes. There are at least
two SSDs sold today that guarantee synchronous write semantics; the
Sun/Oracle LogZilla and the DDRdrive X1. Also, I believe it is more
accurate to describe the root cause as not power
On 15/06/2010 23:46, Christopher George cgeo...@ddrdrive.com wrote:
So why buy SSD for ZIL at all?
For the record, not all SSDs ignore cache flushes. There are at least
two SSDs sold today that guarantee synchronous write semantics; the
Sun/Oracle LogZilla and the DDRdrive X1. Also, I
Bob Friesenhahn wrote:
On Tue, 15 Jun 2010, Arne Jansen wrote:
In case of a power failure I will likely lose about as many writes as
I do with SSDs, a few milliseconds.
I agree with your concerns, but the data loss may span as much as 30
seconds rather than just a few milliseconds.
Wait,
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