calculating size of metadata.
Hi there,
we planning to create a pv and vg on a 19,95TB partition running on raid6. One issue I have is the size of the metadata. I am looking for a way to calculate the this size, but unfortunatly, I cannot find a some. Which size should I use?
Thanks in advance.
Jan
Quoted 7 lines · Jan-Hendrik Palic
Hi there,
we planning to create a pv and vg on a 19,95TB partition running on raid6. One issue I have is the size of the metadata. I am looking for a way to calculate the this size, but unfortunatly, I cannot find a some.
Which size should I use?
Depends on how many LVs you intend to have,
and how much LV fragmentation you expect.
I'd estimate 1 to 2 kByte LVM meta data per expected LV, that should be on the safe side.
Signature · 3 lines
: Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com
It's good think about this because running out of metadata space is no fun. We use 181KB for about 300 LVs, where each snapshot is counted as two LVs because of the way it's stored. That's based on the size of the backup. vgs shows 8 MB of metadata used, though:
# vgs --units k -o vg_mda_count,vg_mda_free,vg_mda_size clones vgs #VMda VMdaFree VMdaSize vgs 3 7973.50k 16444.00k
In any event, on a 19,950,000 MB partition, even 64 MB of metadata would represent 0.0006% of the storage. To think of it another way, 64 MB costs roughly 0.03 cents, so allocate plenty.
Signature · 16 lines
Ray Morris [email protected] Strongbox - The next generation in site security: http://www.bettercgi.com/strongbox/ Throttlebox - Intelligent Bandwidth Control http://www.bettercgi.com/throttlebox/ Strongbox / Throttlebox affiliate program: http://www.bettercgi.com/affiliates/user/register.php On Tue, 24 Apr 2012 14:23:31 +0200
Quoted 17 lines · Jan-Hendrik Palic
Hi there,
we planning to create a pv and vg on a 19,95TB partition running on raid6. One issue I have is the size of the metadata. I am looking for a way to calculate the this size, but unfortunatly, I cannot find a some. Which size should I use?
Thanks in advance.
Jan
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Hi,
Quoted 2 lines · Ray Morris
It's good think about this because running out of metadata space is no fun.
We had this problem already on an other system. We had to migrate to another storage with pain. The new storage has a larger space for the metadata for sure. .-)
But I want to understand and not only set this size to an high value. Therefore this question here.
Quoted 7 lines
We use 181KB for about 300 LVs, where each snapshot is counted as two LVs because of the way it's stored. That's based on the size of the backup. vgs shows 8 MB of metadata used, though:
# vgs --units k -o vg_mda_count,vg_mda_free,vg_mda_size clones vgs #VMda VMdaFree VMdaSize vgs 3 7973.50k 16444.00k
Thank you and Lars for your replies. If I understand you right, I have to look to the count of LVs I will have in the future and not only on the size of my volumegroup.
Ok.
Quoted 3 lines
In any event, on a 19,950,000 MB partition, even 64 MB of metadata would represent 0.0006% of the storage. To think of it another way, 64 MB costs roughly 0.03 cents, so allocate plenty.
Lars stated in his mail to this list, that one entry for a LV should be less than 1kb. So if I calculate 2kb for this entry, I will be safe. I checked this here and I can confirm this.
If I have a metadata space of 64MB, I am able to create 32000 different LV (without snapshots). Right?
Well, that is enought, even with snapshots,
Anyway ... thank you for my enlightment. .-)
Best regards
Jan