Warning: DAOS object minimum participation size = 4096, which is below the minimum recommended value of 64000
Category Lotus Notes and Domino Issues DAOS
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Help file in Domino Administrator 8.5.2 says:
"Minimum size of object before Domino will store in DAOS : The minimum total size, in bytes, of any attachment to be consolidated (the default is 4096 bytes). Enter a number. Consolidating attachments of very small size is not worth the processing effort because it does not yield much disk space saving."
4096 bytes is 4 Kbytes, and that's what we have used to configure DAOS on our servers from its introduction in release 8.0. However, after installing one of the maintenance releases on the server (currently at 8.5.2FP2 on AIX 5.3 64-bit), it now displays this message on the console after starting up:
"Warning: DAOS object minimum participation size = 4096, which is below the minimum recommended value of 64000".
After some digging, I discovered that the help file fails to mention that the default value in this case is not the recommended value (ie. not anymore). That's a bit odd, because usually you want your default to be the recommended value. In this case, the default value is the minimum allowed value, according to the Notes and Domino Wiki entry on DAOS:
"“Minimum size of object before Domino will store in DAOS” (bytes): The default is 4096. 64,000 is recommended."
I contacted IBM Tech Support on this, and this is what they told me:
"Originally the recommended minimum size to use for the 'Minimum size of object' was 4096 bytes, however in later releases this has been increased to 64000 bytes as it was found that in most cases the gains from storing such small attachments was not enough for the processing required. So, for your version of Domino the recommended value for this setting is "64000" and the help file is out of date at this time. Also, please note that this value is set in bytes, meaning that 4096 bytes equates to 4KB, similarly 64000 is for about 64Kb attachments. "
Note the "about" before "64Kb" because it's 4096 bytes that comes to exactly 4 Kbytes, while 6400 bytes comes to 62.5 Kbytes, if you are using 1 Kbyte = 1024 bytes conversion factor. If one wants to go for exactly 64 Kbytes limit, then the actual number would be 65536 bytes.
We used DAOS from the day it was introduced and we went with the original default/recommended value of 4096. Back then, enabling DAOS gave us some very good results (see my original "DAOS Rocks!" post), and I guess we were lucky not to get any noticeable performance degradation resulting from setting our minimum size of DAOS attachments to such a small number (as per today's updated recommendations).
Recently, we had to temporarily disable DAOS on two of the three mail servers in the cluster so that we could copy all mail files to another server at the OS level. This gave me another opportunity to compare the "before" and "after" DAOS numbers. This time we went with 1 Mbyte limit for DAOS inclusion (ie. 1048576 bytes), instead of the original setting of 4 Kbytes (4096 Kbytes), and later lowered it to 0.5 Mbyte (524288 bytes).
smail: 552 files (shared mailboxes)
mail: 2,943 files (personal mailboxes)
These results show that by setting the minimum size of DAOS attachments to 1 MB, we recovered 93 GB of space. By lowering the limit to 0.5 MB, we recovered additional 20 GB.
More Info on DAOS:
DAOS Best Practices - Optimum Minimum Size For Participation
http://www-10.lotus.com/ldd/dominowiki.nsf/dx/daos-best-practices#Optimum+Minimum+Size+For+Participation
Bookmark :
Help file in Domino Administrator 8.5.2 says:
"Minimum size of object before Domino will store in DAOS : The minimum total size, in bytes, of any attachment to be consolidated (the default is 4096 bytes). Enter a number. Consolidating attachments of very small size is not worth the processing effort because it does not yield much disk space saving."
4096 bytes is 4 Kbytes, and that's what we have used to configure DAOS on our servers from its introduction in release 8.0. However, after installing one of the maintenance releases on the server (currently at 8.5.2FP2 on AIX 5.3 64-bit), it now displays this message on the console after starting up:
"Warning: DAOS object minimum participation size = 4096, which is below the minimum recommended value of 64000".
After some digging, I discovered that the help file fails to mention that the default value in this case is not the recommended value (ie. not anymore). That's a bit odd, because usually you want your default to be the recommended value. In this case, the default value is the minimum allowed value, according to the Notes and Domino Wiki entry on DAOS:
"“Minimum size of object before Domino will store in DAOS” (bytes): The default is 4096. 64,000 is recommended."
I contacted IBM Tech Support on this, and this is what they told me:
"Originally the recommended minimum size to use for the 'Minimum size of object' was 4096 bytes, however in later releases this has been increased to 64000 bytes as it was found that in most cases the gains from storing such small attachments was not enough for the processing required. So, for your version of Domino the recommended value for this setting is "64000" and the help file is out of date at this time. Also, please note that this value is set in bytes, meaning that 4096 bytes equates to 4KB, similarly 64000 is for about 64Kb attachments. "
Note the "about" before "64Kb" because it's 4096 bytes that comes to exactly 4 Kbytes, while 6400 bytes comes to 62.5 Kbytes, if you are using 1 Kbyte = 1024 bytes conversion factor. If one wants to go for exactly 64 Kbytes limit, then the actual number would be 65536 bytes.
We used DAOS from the day it was introduced and we went with the original default/recommended value of 4096. Back then, enabling DAOS gave us some very good results (see my original "DAOS Rocks!" post), and I guess we were lucky not to get any noticeable performance degradation resulting from setting our minimum size of DAOS attachments to such a small number (as per today's updated recommendations).
Recently, we had to temporarily disable DAOS on two of the three mail servers in the cluster so that we could copy all mail files to another server at the OS level. This gave me another opportunity to compare the "before" and "after" DAOS numbers. This time we went with 1 Mbyte limit for DAOS inclusion (ie. 1048576 bytes), instead of the original setting of 4 Kbytes (4096 Kbytes), and later lowered it to 0.5 Mbyte (524288 bytes).
smail: 552 files (shared mailboxes)
mail: 2,943 files (personal mailboxes)
|
File system
|
DAOS off,
all attachments stored inside NSFs |
DAOS on,
with 1 MB limit |
DAOS on,
0.5 MB limit | ||||
|
path
|
total allocated
|
free
|
used
|
free
|
used
|
free
|
used
|
| /opt/lotus/notesdata/mail |
707,788,800
|
163,260,780
|
544,528,020
|
334,571,836
|
373,216,964
|
376,573,016
|
331,215,784
|
| /opt/lotus/notesdata/smail |
63,963,136
|
14,276,104
|
49,687,032
|
27,849,784
|
36,113,352
|
32,015,724
|
31,947,412
|
| /opt/lotus/DAOS |
340,787,200
|
340,734,816
|
52,384
|
253,309,740
|
87,477,460
|
228,316,596
|
112,470,604
|
| TOTAL (Kbytes) |
594,267,436
|
496,807,776
|
475,633,800
| ||||
| TOTAL (Gbytes) |
567
|
474
|
454 | ||||
These results show that by setting the minimum size of DAOS attachments to 1 MB, we recovered 93 GB of space. By lowering the limit to 0.5 MB, we recovered additional 20 GB.
More Info on DAOS:
DAOS Best Practices - Optimum Minimum Size For Participation
http://www-10.lotus.com/ldd/dominowiki.nsf/dx/daos-best-practices#Optimum+Minimum+Size+For+Participation
Comments
Posted by Ulrich Krause At 12:34:11 AM On 06/05/2011 | - Website - |
Remember, Power running i5 should have a min of 1MB.
Posted by Darren Duke At 12:45:45 PM On 05/05/2011 | - Website - |