Feedback on used hardware choice (Dell R730)

[Ericloewe]

Hmm I think I could get a lot more out of file level dedup than block level. Is that an option?

You can do all sorts of things at the filesystem level, but that's beyond ZFS' scope.

Reading the docs it looks like I can choose to dedup for individual directories

No, but individual datasets.

Would be nice if there was a “lazy” dedup feature that could run in quiet hours and build the ddt temporarily for the task.

That is a feature that would require Block Pointer Rewrite, and as such is unlikely to happen anytime soon.

 

[HoneyBadger]

Reading the docs it looks like I can choose to dedup for individual directories, but if it creates a level of indirection for io and ddt entries for all blocks in the whole pool as soon as it’s used for anything, well that seems to be of limited utility.

The dedup path isn't engaged, but obviously if they're all sharing the same physical vdevs the metadata workload can choke out the other non-dedup datasets.

Hmm I think I could get a lot more out of file level dedup than block level. Is that an option?

Not within ZFS unfortunately - you'd have to file-level deduplicate before putting the data on the server.

Would be nice if there was a “lazy” dedup feature that could run in quiet hours and build the ddt temporarily for the task.

Unfortunately there's no offline dedup in ZFS either.

 

[jgreco]

Hmm I think I could get a lot more out of file level dedup than block level. Is that an option?

There's no special feature, if that's what you're asking. Those of us who have been UNIX sysadmins for some time are familiar with tools like Phil Karn's dupmerge. These aren't really specific to ZFS or anything.

 

[shanemikel]

There's no special feature, if that's what you're asking. Those of us who have been UNIX sysadmins for some time are familiar with tools like Phil Karn's dupmerge. These aren't really specific to ZFS or anything.

Still it would be nice if it was transparent. Does dupmerge use symlinks or hardlinks?

If so, one needs to account for that when modifying files if the shared targets should not be modified. Similarly it may change behavior of cp, rsync, etc. Some software may even behave differently during read.

 

[shanemikel]

If I try dedup for some dataset and it turns out to have an unacceptable performance impact, is it difficult to undo and erase the ddt, restore prior behavior on the pool as if it t was never tried?

 

[jgreco]

Does dupmerge use symlinks or hardlinks?

Phil Karn's dupmerge uses hardlinks. I don't think it's been updated for nearly 20 years, and I do know for certain that there are somewhat newer tools that do the same (or similar?) job, I just tend to use the same ones I've historically used.

Similarly it may change behavior of cp, rsync, etc.

This is a natural hazard of hacking at the inode level. In some cases, it might be prudent to toss uchg (or maybe others) onto the file flags to force attempted changes to fail out.

If I try dedup for some dataset and it turns out to have an unacceptable performance impact, is it difficult to undo and erase the ddt, restore prior behavior on the pool as if it t was never tried?

My recollection is that the DDT never goes away, and that blocks referenced through the DDT will continue to be need to be indirected through the DDT. You should be able to return to similar performance by removing all the dedup'ed data (the ddt entry refcount drops to zero, the ddt entry goes away).

 

[shanemikel]

My recollection is that the DDT never goes away, and that blocks referenced through the DDT will continue to be need to be indirected through the DDT. You should be able to return to similar performance by removing all the dedup'ed data (the ddt entry refcount drops to zero, the ddt entry goes away).

So, assuming I can find the deduped data, I could un-dedup it by copying it to a non-dedup enabled location (or a different path in the same dataset after disabling). Would this necessitate the deletion of any snapshots containing dedup data as well?

 

[Ericloewe]

Would this necessitate the deletion of any snapshots containing dedup data as well?

Yes

 

[husky1055]

It seemed like I have been using Freenas and Truenas for a long time. My small server is getting old and the DIY Supermicro MB, Xeon cpu and ram and PS scare me. The Dell R730 discussion leading to the various raid controllers was very helpful and the tutorial about HBA, IT mode and different PERC model will help me with my next project. So thank you all for this really informative thread.

 

[ChrisRJ]

Funny . Having a Supermicro board for two years now, Dell and the details on proprietary hardware scare me ...

 

[Ericloewe]

What do you mean you don't enjoy looking up which SFF-8643 cables you need to support NVMe SSDs on an R630 10-bay backplane with a PCIe x16 retimer board when using a controller in an expansion slot instead of the integrated SAS card?

 

[husky1055]

My need is very limited, i.e. 4 drives and Plex server. So I just wonder if this Ebay Dell is OK for my use case:

Dell T320

Not sure about flashing the H310 to IT mode. But my B plan is to buy an IT mode controller from the Ebay seller posted above.

 

[jgreco]

What do you mean you don't enjoy looking up which SFF-8643 cables you need to support NVMe SSDs on an R630 10-bay backplane with a PCIe x16 retimer board when using a controller in an expansion slot instead of the integrated SAS card?

<mod hat on>Forum participants are reminded that while prebuilt servers are nice when everything works out, it can be painfully masochistic to have to refurbish them when repurposing them. Discussions of the details can be technically difficult and could be deemed unfriendly, actively hostile, and/or anti-social behaviour. Please note the Forum Rules. You have been warned.</mod>

(and for heaven's sake, if you don't have a sense of humor, get a Usenet subscription and visit rec.humor.funny or something)

 

[HoneyBadger]

My need is very limited, i.e. 4 drives and Plex server. So I just wonder if this Ebay Dell is OK for my use case:

Dell T320

Not sure about flashing the H310 to IT mode. But my B plan is to buy an IT mode controller from the Ebay seller posted above.

I would fork this off into another discussion, as the subject of this thread is the R730 and it could confuse a new arrival. We can then dig into your needs in a little more detail there as well.

But in brief, that server should be fine for your needs - the H310 can and should be reflashed to LSI firmware, and bear in mind that the Dell drive trays may not be included and will need to be purchased separately.

 

[husky1055]

I would fork this off into another discussion, as the subject of this thread is the R730 and it could confuse a new arrival. We can then dig into your needs in a little more detail there as well.

But in brief, that server should be fine for your needs - the H310 can and should be reflashed to LSI firmware, and bear in mind that the Dell drive trays may not be included and will need to be purchased separately.

Thank you and please forgive me for diverting from the subject. If I found a Dell Tower equivalent for the R730I would have gone into that direction.

 

[Ericloewe]

<mod hat on>Forum participants are reminded that while prebuilt servers are nice when everything works out, it can be painfully masochistic to have to refurbish them when repurposing them. Discussions of the details can be technically difficult and could be deemed unfriendly, actively hostile, and/or anti-social behaviour. Please note the Forum Rules. You have been warned.</mod>

"Pre-built" is a misnomer born out of a misunderstanding. They're pray-built, as in, pray that the OEM doesn't think you're insane or worse - trying to actively save money.

 

[HoneyBadger]

Thank you and please forgive me for diverting from the subject. If I found a Dell Tower equivalent for the R730I would have gone into that direction.

Not a problem, you may also get more of an audience with similar background or interest in the same smaller/tower style server. But for reference, the tower equivalent of the R730 is the PowerEdge T630.

Feel free to @ tag me when the new thread is posted if you like and I'll review the proposed build in detail.

 

[rvassar]

If you remove the battery, I'd suspect it's fine to lobotomize them.

Removing the battery + JBOD is about as close as you can get to IT mode.

 

[rvassar]

Not sure about flashing the H310 to IT mode. But my B plan is to buy an IT mode controller from the Ebay seller posted above.

I've been running an H310 in IT mode for years. I haven't verified your seller, but when done correctly, it just works.

 

[HoneyBadger]

Removing the battery + JBOD is about as close as you can get to IT mode.

Actually, the H710 can be fully converted into a SAS2308 thanks to the efforts of dedicated hardware hackers.

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