12 disk setup SATA setup for VM storage

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Jon K

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Try turning on sync=always and testing again. I'm assuming you'll be setting that for your iscsi zvols, and with your current testing, you're not really going through your SLOG for writes.

Forgive my newbness but where is that set? I have been using the UI mostly so far except for testing write/read.
 

jgreco

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Ugh makes sense. More to think about lol. I did see the padding in that chart. So help me understand - does volblocksize happen at the pool or zvol?

It's basically the recordsize used for the zvol.

It would seem the parity is calculated out at the pool level especially considering the applicable configuration seems to follow the vdev layout/pool.

No, RAIDZ is unlike hardware RAID5. There are no precomputed locations for parity data. ZFS normally uses a variable block size, so again back to the chart the first block stored is 32K which is ten disk sectors. This or other multiples-of-four are going to be the preferred size because they give you the "expected" RAID5-like space consumption. However, consider a 4K block. This has to be written with a parity block so it is 100% overhead. Bleh. But no RAID5 write hole, and we recommend RAIDZ be used for large sequential file storage at which it is hellishly efficient.

What do most people use for iSCSI?

Mirrors. (And I say that with a perfectly straight face knowing it's not what you're asking.)

Also, on the topic but not, does FreeNAS support multipathing for iSCSI?

Yes. Even with VAAI support for... I can't remember which and the VM filer here is offline for a side project. Sorry.
 

Jon K

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Awesome info on all fronts jgreco. One last question before I can set my mind down and actually get some work done today. Why is it that when I turn compression off I get higher measured IOPs using zpool iostat 1 than with it on? I read the articles above but unless I missed it I didn't see that referenced.

Also, a poster above said to set sync=always but I am not sure where to do that. I don't have any datasets yet, just a volume:

gXZlrUV.png


I understand vdev, zpool, some what of the SLOG and ZIL, but zvol and dataset is a little confusing.
 

gpsguy

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Given that the OP is a storage admin, whose company probably pays large sums of $$$ for SAN support, I was hoping that pointing him in the right direction would free up some of your time for answers that are readily available (answered week after week) on the forums.

If users knew the real cost of your (billing/consulting) time, perhaps they'd spend some time searching for answers first.

Wow, I just gotta stop answering threads... that's like the fourth time today someone's slid in moments before me with a good answer.
 

Jon K

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Given that the OP is a storage admin, whose company probably pays large sums of $$$ for SAN support, I was hoping that pointing him in the right direction would free up some of your time for answers that are readily available (answered week after week) on the forums.

If users knew the real cost of your (billing/consulting) time, perhaps they'd spend some time searching for answers first.

Apologies - you need a Netapp ONTAP setup or EQL/Compellant EMC, feel free to reach out - new to FreeNAS and thought I'd be able to ping the community for feedback and answers. I am sure Netapp LIFS, SVMs, aggregates, etc. would make a lot of people ask questions. Trying to equate ZFS terminology to things I already know. The manual isn't good at that. It only barely talks about ZIL and SLOG, for instance. It also has a very peculiar section on LACP not working well in virtual environments... (I am both a storage admin and virtualization engineer). I too work for good money so I didn't cruise the guide too much today and instead thought some friendly convo would be welcome.
 

gpsguy

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I've worn both those hats too. I enjoyed using Compellent (bought into it, before the Dell aquistion).

...I am both a storage admin and virtualization engineer

If you end up using FreeNAS, I would encourage you to stop by from time to time and lend a hand. TIA
 

Jon K

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I've worn both those hats too. I enjoyed using Compellent (bought into it, before the Dell aquistion).



If you end up using FreeNAS, I would encourage you to stop by from time to time and lend a hand. TIA

I intend to hang around for sure - I like FreeNAS so far, just trying to get more familiar with the ZFS aspect. COW is intriguing. Because I've been involved in Netapp lately I am finding an awful lot of parallels. Was speaking with a co-worker the other day and said I wish Netapp was a little more transparent so I could determine exactly what they're running on the back - though, wouldn't that be nice lol. I do know there was some pending lawsuit/etc. regarding Netapp and Oracle/ZFS so that's interesting.

Compellent is nice - it does a few things differently but I like it. We're moving from many, many Equallogics/Compellents to a large multi node FAS8020 setup from Netapp. I am anxious to go NFS though iSCSI has been rock solid. We're all blade chassis now w/ Cisco FEX and 10 GbE so NFS should perform nice and has auto-grow, thin provision, dedupe on Netapp, etc. We've moved from SAN replication to Zerto, so I am no longer shipping huge LUNs over inter-facility links. The grass is getting greener! But I digress, I am really interested in FreeNAS and ZFS as a whole. Printing the 9.10 user guide today :) Anxious for FreeNAS 10 - saw a teaser on youtube, looks really cool.
 

jgreco

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Awesome info on all fronts jgreco. One last question before I can set my mind down and actually get some work done today. Why is it that when I turn compression off I get higher measured IOPs using zpool iostat 1 than with it on? I read the articles above but unless I missed it I didn't see that referenced.

Offhand guess would be that when you compress the data you're probably pushing less data to the pool. If you disable compression, more data is stored. More IOPS. Not useful IOPS though, since it's more IOPS for about the same amount of work.

Also, a poster above said to set sync=always but I am not sure where to do that. I don't have any datasets yet, just a volume:

gXZlrUV.png


I understand vdev, zpool, some what of the SLOG and ZIL, but zvol and dataset is a little confusing.

ZFS creates its big storage pool out of vdevs. Looking at the big picture of the "back end", the goal of ZFS is to create a storage pool and then be able to do useful things with the storage. The characteristics of the pool are defined by the choice of vdev type, and any modifiers such as SLOG or L2ARC.

You can grow the pool at any time by adding more vdevs. You cannot remove vdevs, a significant weakness of ZFS currently.

Now let's move to the "front end." ZFS allows us to use its pool and allocate those resources to storage needs.

Think of a dataset as being a filesystem created using (part of?) the pool as storage.

A zvol is a block storage abstraction that you create using (part of?) the pool as storage.
 

jgreco

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If users knew the real cost of your (billing/consulting) time, perhaps they'd spend some time searching for answers first.

Don't be too hard on 'im, in some ways familiarity with existing storage technologies helps but also hurts when you're learning ZFS.
 
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