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SnEptUne
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PostPosted: Tue Jan 18, 2022 5:16 pm    Post subject: SSD Free Space Requirement Reply with quote

Is it still required to leave 20% free space for SSD these days with > 10TB on enterprise?

My 12TB is getting 90% full and is getting spammed by Nagios alert, but I still have 1.2TB. Is it safe to reduce the threshold to 95% (so 600GB free)? Or do we need to keep it at 20% free (2.4TB of free space is really wasteful and expensive, especially on enterprise drive)?
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mike155
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PostPosted: Tue Jan 18, 2022 7:23 pm    Post subject: Reply with quote

Which drives do you have (manufacturer / model)?

Is it a RAID system? Hardware-RAID or Software RAID?

Which filesystem do you use?

Do you run fstrim at regular intervals?
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SnEptUne
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PostPosted: Tue Jan 18, 2022 10:57 pm    Post subject: Reply with quote

mike155 wrote:
Which drives do you have (manufacturer / model)?

Is it a RAID system? Hardware-RAID or Software RAID?

Which filesystem do you use?

Do you run fstrim at regular intervals?


Yes, it is running RAID 10, software RAID. Filesystem is just ext4, so nothing fancy. I am not running fstrim, I thought discard option from ext4 should suffice. Does running RAID affect the free space requirement?
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mike155
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PostPosted: Tue Jan 18, 2022 11:47 pm    Post subject: Reply with quote

Modern SSDs come with their own reserved free space. That's why I asked for the manufacturer and the model of your drives. It could well be that you don't need free space in your file system, because your drives have sufficient reserved free space. Take a look at the data sheet of your drives to find out.

It's important to regularly send trim commands to the SSDs. Both filesystem discard and fstrim work well, although the latter is recommended.

It could be that a RAID controller removes trim commands and doesn't send them to the drives. If that's the case, it could well be that your drives are already in the state where all 'official' space is occupied. Filling up your filesystem wouldn't make it worse.


Last edited by mike155 on Tue Jan 18, 2022 11:53 pm; edited 1 time in total
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SnEptUne
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PostPosted: Tue Jan 18, 2022 11:53 pm    Post subject: Reply with quote

mike155 wrote:
Modern SSDs come with their own reserved free space. That's why I asked for the manufacturer and the model of your drives. It could well be that you don't need free space in your file system, because your drives have sufficient reserved free space. Take a look at the data sheet of your drives to find out.

It's important to regularly send trim commands to the SSDs. Both filesystem discard and fstrim work well, although the latter is recommended.

It could be that a RAID system removes trim commands and doesn't send them to the drives. If that's the case, it could well be that your drives are already in the state where all 'official' space is occupied. Filling up your filesystem wouldn't make it worse.


I see, sorry I missed your first question. The model is micron 5100 ECO, 7.68TB in RAID 10.
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mike155
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PostPosted: Wed Jan 19, 2022 12:14 am    Post subject: Reply with quote

Anandtech writes:
Quote:
Spare area ranges from a minimum of 15% on the density-focused 5100 ECO up to a massive 60% on the performance-focused 5100 MAX.

I think you can fill your filesystem up to 95%. It's probably more important to find out whether your RAID controller forwards TRIM commands to your drives...
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